Aerosols are a ubiquitous component of the atmosphere, playing pivotal roles in air quality and climate. This thesis explores the way these particles come to be, and their roles in these atmospheric processes.
\r\n\r\nAerosols form from a variety of anthropogenic and biogenic activities, processes which are very prominent in urban settings. In Los Angeles, the last decade of research has been dominated by the role of summertime secondary organic aerosol (SOA) in contributing to particulate matter (PM). Here, we make observations in the equinox seasons and in the winter and detail the formation of atmospheric aerosols in these seasons. Using aerosol mass spectrometry, we demonstrate that ammonium nitrate persists as one of the dominant secondary aerosol components despite dramatic reductions in nitrogen oxide (NO\u2093) emissions. Further, we show that this ammonium nitrate is not measured by routine air quality measurements, biasing regulatory PM2.5 measurements. In the wintertime, similar techniques demonstrate that primary organic aerosol, as opposed to secondary, is an important component of the PM2.5, contrary to the prevailing narratives that SOA dominates the aerosol mass.
\r\n\r\nAt global scales, the role of these aerosols in cloud formation and climate processes is of primary interest. While a variety of physicochemical properties of aerosols are important in the formation of cloud droplets, we focus here on the specific process of organic surface-partitioning. It has been suggested that in phase-separated aerosol, organic-rich surface layers can depress the surface tension of the particles, lowering their barrier to activate into cloud droplets. We assess this propensity for surface tension depression in two SOA systems, \u03b1-pinene and \u03b2-caryophyllene. Synergizing laboratory measurements, a thermodynamic model, and field data, it is shown that surface-active organics in these SOA systems can impact their hygroscopicity, though perhaps not sufficiently to warrant inclusion of these processes in global-scale models.
", "doi": "10.7907/dham-e191", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16447", "collection": "thesis", "collection_id": "16447", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302024-161447176", "primary_object_url": { "basename": "Buenconsejo_Caltech_Thesis_Final.pdf", "content": "final", "filesize": 92643355, "license": "other", "mime_type": "application/pdf", "url": "/16447/1/Buenconsejo_Caltech_Thesis_Final.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Clearing the Air: A Chemical Approach to Understanding Secondary Organic Aerosol Formation From Volatile Chemical Products", "author": [ { "family_name": "Buenconsejo", "given_name": "Reina S.", "orcid": "0000-0002-0162-905X", "clpid": "Buenconsejo-Reina-S" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Understanding sources of air pollution is critically important as ~7 million premature deaths are associated with poor air quality. A key component of urban air quality is secondary organic aerosol (SOA), a type of particulate matter that contributes smog. SOA is formed via the reactive oxidation of volatile organic chemicals (VOCs), gas-phase compounds often emitted from anthropogenic sources. Historically, SOA formation and VOC emissions have been driven by on-road mobile sources. In recent years, however, other sources, such as consumer and industrial solvents - so called volatile chemical products (VCPs) - have become increasingly more important. SOA also impacts climate change, as particulate matter affects global radiative forcing. \r\n\r\nCharacterizing the chemistry and SOA formation from VCPs can elucidate our understanding of modern urban air pollution, particularly as we try to uncover recent stagnation in air quality. Because VCPs are comprised of hundreds of individual chemical compounds, it is exceedingly difficult to study and characterize each one individually. By contrast, understanding these compounds through a chemistry lens can help to make broader generalizations about larger classes of compounds. \r\n\r\nThis dissertation looks at the chemistry leading to SOA formation from several chemicals that make up VCPs. Specifically, this work looks at benzyl alcohol and ethoxyethanol. These compounds are used in personal care products, cleaning products, architectural coatings and adhesives. Understanding the reactivity of these compounds can help us understand more broadly the chemistry and SOA potential of other chemicals in VCPs that have similar chemical structures.", "doi": "10.7907/6sq5-5m61", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:15261", "collection": "thesis", "collection_id": "15261", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012023-202236185", "type": "thesis", "title": "Insights into the Sources of Atmospheric Aerosols and Greenhouse Gases in California", "author": [ { "family_name": "Schulze", "given_name": "Benjamin Christopher", "orcid": "0000-0002-6405-8872", "clpid": "Schulze-Benjamin-Christopher" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Frankenberg", "given_name": "Christian", "orcid": "0000-0002-0546-5857", "clpid": "Frankenberg-Christian" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "A substantial fraction of atmospheric science research is motivated by uncertainties in the sources of urban particulate matter and greenhouse gases. Such a focus is justified, as particulate matter exposure is responsible for up to nine million annual premature deaths globally, while climate change is rapidly altering ecosystems across the world. Recognizing the urgency of these interrelated problems, regulatory agencies in the U.S. and elsewhere have sought to limit emissions contributing to air quality degradation and global warming.
\r\n \r\nIn this dissertation, we use a combination of ambient measurements, statistical models, and computational models to identify the sources of urban particulate matter and methane in multiple locations in California. In Los Angeles, we investigated the effects of reductions in mobile source pollutant emissions (i.e., on-road and off-road vehicles) on ambient aerosol concentrations. Mobile sources have historically accounted for the dominant fraction of urban particulate matter in Los Angeles, but despite notable reductions in their emissions over the last decade, ambient aerosol concentrations have not declined appreciably. Measurements using an Aerosol Mass Spectrometer demonstrate the complex interplay of direct (i.e., intended) and indirect effects of simultaneous reductions in organic aerosol (OA) precursor and nitrogen oxide emissions from these sources. Mobile sources are found to account for a modest and declining fraction of the total aerosol burden, while the contributions of non-traditional sources such as volatile chemical products (e.g., paints and coatings, cleaning products, adhesives and sealants) have increased. Simulations of organic and inorganic aerosol formation informed by in-situ measurements are developed to identify possible targets of future regulatory efforts.
\r\n\r\nIn the San Joaquin Valley, we used airborne measurements of methane fluxes to evaluate dairy emissions inventories used by state regulatory agencies for policy development. Dairy operations currently account for nearly half of the state\u2019s methane emissions, and recent legislation has mandated a 40% reduction in emissions by 2030. Observed methane fluxes align well with emission inventory predictions and demonstrate the utility of airborne flux measurements to track emission reduction progress in the future. Factor analysis of a combined dataset of greenhouse gas and volatile organic compound concentrations indicates dairy operations account for ~65% of total methane emissions in the southern San Joaquin Valley, with the remainder attributed to fugitive oil and gas emissions.
", "doi": "10.7907/zay2-1v59", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15037", "collection": "thesis", "collection_id": "15037", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09292022-204343735", "type": "thesis", "title": "Development of Numerical Models to Advance the Understanding of Air Quality in Los Angeles", "author": [ { "family_name": "Pennington", "given_name": "Elyse Ann", "orcid": "0000-0003-1736-2342", "clpid": "Pennington-Elyse-Ann" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Wang", "given_name": "Yuan", "orcid": "0000-0001-6657-8401", "clpid": "Wang-Yuan" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Atmospheric pollutants such as particulate matter (PM) and ozone (O\u2083) are harmful to human health and intensify climate change. Secondary organic aerosol (SOA) is a main component of PM and is formed via atmospheric oxidation reactions of thousands of gas- and aerosol-phase precursors. Regional-scale chemical transport models predict the formation of these pollutants by representing natural and human emissions of hundreds of species and their subsequent chemical and physical processing in the atmosphere. These models are useful in the absence of detailed measurements and allow researchers to investigate the impact of changing emissions and weather. Los Angeles has unique meteorology and anthropogenic emissions which lead to dangerous pollution events and make this region an important area to study SOA, PM, and O\u2083 formation. As vehicles have become cleaner and their emissions have declined, other sources of emissions have become increasingly important. One important category of emissions is volatile chemical products (VCPs), which are consumer and industrial products that have high volatile organic compound (VOC) emissions that have not been well-constrained or studied in relation to their SOA and O\u2083 formation potential. In this dissertation, I use the Community Multiscale Air Quality (CMAQ) model to represent the air quality of the Los Angeles Basin. First, a new chemical mechanism is developed to represent the formation of SOA from VCPs, implemented in the CMAQ model to simulate 2010 California, and the impact of VCPs on atmospheric pollutants is quantified. Next, we created contemporary inputs to CMAQ by simulating the meteorology, emissions, and land surface of the Los Angeles Basin in 2020. Lastly, the new inputs and chemistry are applied to CMAQ to understand current air quality issues in Los Angeles. We quantify the impact of VCPs on SOA, PM, O\u2083, and other pollutants in both 2010 and 2020. The apportionment of other emission sources and the impact of the COVID-19 pandemic are investigated, and pollutant concentrations are compared to measurements made throughout the Basin and specifically in Pasadena. This works demonstrates the importance of intentional policies to mitigate harmful air pollution events. Limiting NO\u2093 emissions is not sufficient to limit the formation of ozone and PM, and there must be a simultaneous reduction of VOC emissions.", "doi": "10.7907/cvzw-kt61", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15257", "collection": "thesis", "collection_id": "15257", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012023-170244182", "type": "thesis", "title": "A Novel Algorithm for Inferring the Vertical Distribution of Trace Gases Using Remote Sensing Measurements", "author": [ { "family_name": "Parker", "given_name": "Harrison Alexander", "orcid": "0000-0002-0041-2764", "clpid": "Parker-Harrison-Alexander" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Frankenberg", "given_name": "Christian", "orcid": "0000-0002-0546-5857", "clpid": "Frankenberg-Christian" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Remote sensing is a powerful tool that is used to diagnose sources, sinks, and fluxes of trace gases across different spatial and temporal scales. Ground-based remote sensing measurements of column-averaged dry mole fractions (DMF) of gases such as carbon dioxide (CO\u2082) and carbon monoxide (CO) made by the Total Carbon Column Observing Network (TCCON) are used to validate space-based measurements and better understand the carbon cycle. Surface signals of gas exchange can be masked in the total column values, however, limiting their use in assessment of local surface fluxes. Retrievals of the vertical distribution of trace gases can be used to obtain gas exchange information that is more directly related to changes at the surface but require high precision measurements with less temporal resolution than the TCCON total column measurements. In this thesis, I develop an algorithm, the Temporal Atmospheric Retrieval Determining Information from Secondary Scaling (TARDISS), that infers vertical information, or \u2018partial columns\u2019, from existing, quality-controlled total column data. The TARDISS algorithm does not fit the solar spectra but rather begins with trace gas column retrievals obtained from different spectral bands using the standard TCCON retrievals. TARDISS takes advantage of the fact that different bands have different sensitivities to the same trace gas as a function of altitude and solar zenith angle. We use the TARDISS partial column data to examine estimated surface fluxes in the North American boreal forest and compare them to surface fluxes estimated from tall tower in situ measurements. We also outline changes in air quality from the sudden change in traffic behavior from the COVID-19 lockdown which serves as motivation for the use of the TARDISS-derived lower partial column CO data to examine recent changes in air quality in the South Coast Air Basin.", "doi": "10.7907/xfkf-8t80", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15276", "collection": "thesis", "collection_id": "15276", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022023-045855497", "type": "thesis", "title": "Inference of Global Methane Emissions from Oil and Gas Production", "author": [ { "family_name": "Tribby", "given_name": "Ariana Linnae", "orcid": "0000-0002-6435-4575", "clpid": "Tribby-Ariana-Linnae" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "Resnick Sustainability Institute" }, { "literal": "div_chem" } ], "abstract": "Atmospheric methane plays a significant role in warming the climate. Characterizing its sources and sinks is important for future climate and air quality impacts. Global methane background trends suggest a sustained increase in emissions since 2007. There is no debate that reducing anthropogenic (human-driven) emissions can lead to short-term decreases in atmospheric methane, posing an attractive avenue towards mitigating climate change. Yet, effective policy to limit emissions from energy-related activities relies on accurate emission estimates, and historically, it has been challenging to diagnose both the magnitude and origin of methane leaks from a wide range of facilities and components across production, transmission, storage, and distribution systems. We present a novel Bayesian hierarchical model to improve methane emission estimates on global and regional scales from oil and gas processes. We also present methods to optimize time and cost of model simulations of certain trace gases, including several of which have important climate implications. Finally, we present our efforts in characterizing fossil methane from burgeoning oil production in Oklahoma and Texas using long term ground-based remote-sensing observations combined with Stochastic Time-Inverted Larangian Transport modeling.
", "doi": "10.7907/pjn3-az83", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:14616", "collection": "thesis", "collection_id": "14616", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05252022-162959411", "primary_object_url": { "basename": "Seungkyeum Kim Ph.D. Thesis Ver 2.pdf", "content": "final", "filesize": 2442673, "license": "other", "mime_type": "application/pdf", "url": "/14616/1/Seungkyeum Kim Ph.D. Thesis Ver 2.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Development of Electrochemical Processes for More Practical and Effective Onsite Wastewater Treatment", "author": [ { "family_name": "Kim", "given_name": "Seungkyeum", "orcid": "0000-0002-0948-6452", "clpid": "Kim-Seungkyeum" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Gray", "given_name": "Harry B.", "orcid": "0000-0002-7937-7876", "clpid": "Gray-H-B" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "In spite of the lack of safely managed sanitation and water supply systems, developing countries with rapid urbanization cannot afford to implement advanced treatment technologies that are highly centralized, calling for the development of practical onsite wastewater treatment. As effective yet practical solutions to the water crisis, I have developed high-performance earth-abundant electrocatalysts and an uncoupled electro-peroxone (E-peroxone) prototype reactor that can be applied in and as decentralized wastewater treatment systems. A series of conductive TiO\u2082 nanotube array electrodes are known to be effective for chlorine evolution reaction (CER) for wastewater treatment and oxygen evolution reaction (OER) for water splitting. In order to further enhance their electrocatalytic activities, an ultrathin layer of Al\u2082O\u2083 was deposited onto TiO\u2082 nanotube arrays via atomic layer deposition (ALD). Due to the facilitated formation of Ti\u00b3\u207a and oxygen vacancies by Al\u2082O\u2083 ALD, black TiO\u2082 nanotube arrays with 8 ALD cycles achieved up to 30% enhancement in CER and OER overpotentials in comparison to those without Al\u2082O\u2083 coating. Moreover, the ultrathin Al\u2082O\u2083 overlayer (~2 nm) reduced the charge transfer resistance and increased the electrochemical chemical surface area (ECSA) 3-fold for both reactions. Black TiO\u2082 nanotube arrays with 8 cycles were applied for toilet wastewater treatment and outperformed a dimensionally stable anode (DSA) in terms of chemical oxygen demand (COD) and ammonia reductions. The simplicity of the synthetic procedures and the use of inexpensive metal oxides suggest that Al\u2082O\u2083-deposited TiO\u2082 nanotube arrays can provide a promising approach to wastewater treatment and water splitting as practical alternatives for costly DSAs.
\r\n\r\nThe uncoupled E-peroxone reactor system integrates ozonation with in situ hydrogen peroxide (H\u2082O\u2082) production to generate hydroxyl radicals for wastewater treatment. The E-peroxone process variables such as H2O2 concentration and ozone dose were optimized to maximize the treatment efficiency. Consequently, the system succeeded in reducing COD by 89%, total organic carbon (TOC) by 91%, biochemical oxygen demand (BOD) by 86%, and turbidity by 95% after 90-minute treatment of synthetic graywater. Moreover, the system reclaimed treated wastewater as an electrolyte for H\u2082O\u2082 production for subsequent treatment and maintained over 80% and 70% reductions in COD and TOC, respectively, over four consecutive treatment cycles. This system does not need any chemical additive, utilizes the energy-efficient E-peroxone process, and comprises inexpensive, accessible components. As a result, these advantages significantly reduce the system\u2019s capital and operational costs. The promising results and cost-effectiveness show that it can provide a viable solution for the treatment of graywater and human wastewater in low-resource settings.
", "doi": "10.7907/ab1v-he77", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14494", "collection": "thesis", "collection_id": "14494", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02112022-233628713", "primary_object_url": { "basename": "Vasquez_Dissertation_Final_V2.pdf", "content": "final", "filesize": 5824267, "license": "other", "mime_type": "application/pdf", "url": "/14494/1/Vasquez_Dissertation_Final_V2.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Isomer Separation of Multifunctional Atmospheric Compounds Using Gas Chromatography and Chemical Ionization Mass Spectrometry", "author": [ { "family_name": "Vasquez", "given_name": "Krystal TonyBeth", "orcid": "000-0003-4540-4212", "clpid": "Vasquez-Krystal-TonyBeth" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Oxygenated volatile organic compounds are a group of carbon-containing species that include one or more functional groups. They are formed during oxidation of hydrocarbons in the atmosphere. Afterwards, they readily undergo atmospheric processing, which\u2014depending on their chemical properties\u2014can lead to the formation of harmful pollutants, such as ozone or secondary organic aerosols (SOA). Prolonged exposure to either compound can negatively impact human health.
\r\n\r\nUnfortunately, most existing analytical techniques struggle to quantify the concentrations of the majority of OVOCs due to their characteristic low abundances and high reactivities. In addition, most of these compounds are also made up of a complex mixture of isomers that few instruments are able to resolve. Since even slight changes in structure can impact an OVOC\u2019s atmospheric fate, this can lead to uncertainties when elucidating their chemical mechanisms. As a result, despite decades of research, there are still many outstanding questions pertaining to atmospheric processing of OVOCs and, by extension, their impact on air quality.
\r\n\r\nTo combat this issue, novel instrumentation was developed that can provide accurate, isomer-resolved measurements of a wide variety of OVOCs, which it achieves by combining the sensitive, specific nature of gas chromatography (GC) with the equally sensitive, yet non-invasive aspects of chemical ionization mass spectrometry (CIMS). To showcase its capabilities, these new instrumental methods are applied to the study of isoprene oxidation. More specifically, we report new insights into the isomer-specific loss processes of isoprene-derived hydroxy nitrates. Inclusion of our findings into atmospheric models can greatly improve our simulations of NO\u2093, ozone, and nitric acid.
", "doi": "10.7907/yaz8-qr39", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14528", "collection": "thesis", "collection_id": "14528", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03242022-211905773", "primary_object_url": { "basename": "KensethChristopher_2022_Thesis.pdf", "content": "final", "filesize": 46922631, "license": "other", "mime_type": "application/pdf", "url": "/14528/1/KensethChristopher_2022_Thesis.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Formation, Abundance, and Evolution of Molecular Products in \u03b1-Pinene and \u03b2-Pinene Secondary Organic Aerosol", "author": [ { "family_name": "Kenseth", "given_name": "Christopher M.", "orcid": "0000-0003-3188-2336", "clpid": "Kenseth-Christopher-M" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The atmospheric oxidation of \u03b1-pinene and \u03b2-pinene (C10H16), emitted in appreciable quantities from forested regions (~85 Tg y\u20131), contributes significantly to the global burden of secondary organic aerosol (SOA), a substantial component (15\u201380% by mass) of atmospheric fine particulate matter (PM2.5), which exerts large but uncertain effects on climate as well as adverse impacts on air quality and human health. Deciphering the molecular composition, and in turn formation and aging mechanisms, of \u03b1-pinene and \u03b2-pinene SOA is essential to reducing uncertainty in assessment of their environmental and health impacts. However, molecular characterization of \u03b1-pinene and \u03b2-pinene SOA is significantly hindered by their chemical complexity. In this work, we constrain the formation, abundance, and evolution of molecular products in SOA derived from ozonolysis and photooxidation of \u03b1-pinene and \u03b2-pinene using a combination of laboratory experiments, liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS), and organic synthesis. Through detailed MS/MS analysis, coupled with 13C isotopic labeling and OH scavenging, we identify a suite of dimeric compounds (C15\u201319H24\u201332O5\u201311) formed from synergistic O3 + OH oxidation of \u03b2-pinene (i.e., accretion of O3- and OH-derived products/intermediates). Informed by these structural analyses, together with 18O isotopic labeling and H/D exchange, we synthesize the first authentic standards of several major dimer esters identified in SOA from ozonolysis of \u03b1-pinene and \u03b2-pinene and elucidate their formation mechanism from targeted environmental chamber experiments. Additionally, we synthesize a series of pinene-derived carboxylic acid and dimer ester homologues and find that the ESI efficiencies of the dimer esters are 19\u201336 times higher than that of commercial cis-pinonic acid, a common quantification surrogate. Finally, we investigate the aqueous (photo)chemistry (kinetics, products, and mechanisms) of the carboxylic acid and dimer ester homologues at cloudwater-relevant concentrations as a function of pH.
", "doi": "10.7907/bj1b-1441", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14445", "collection": "thesis", "collection_id": "14445", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12102021-231944176", "primary_object_url": { "basename": "KjeldbjergCamilla2022Thesis.pdf", "content": "final", "filesize": 57009594, "license": "other", "mime_type": "application/pdf", "url": "/14445/1/KjeldbjergCamilla2022Thesis.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "The Effects of Confinement in Active Matter: the Casimir Effect, Partitioning, and Hindered Diffusion", "author": [ { "family_name": "Kjeldbjerg", "given_name": "Camilla Maria", "orcid": "0000-0003-2224-0534", "clpid": "Kjeldbjerg-Camilla-Maria" } ], "thesis_advisor": [ { "family_name": "Brady", "given_name": "John F.", "orcid": "0000-0001-5817-9128", "clpid": "Brady-J-F" } ], "thesis_committee": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Brady", "given_name": "John F.", "orcid": "0000-0001-5817-9128", "clpid": "Brady-J-F" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Shapiro", "given_name": "Mikhail G.", "orcid": "0000-0002-0291-4215", "clpid": "Shapiro-M-G" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Active matter describes a class of materials for which constituent \"particles\" convert chemical energy into mechanical motion leading to self-propulsion (swimming). The origins of this swimming motion for both biological and synthetic constituents is a thriving area of research. However, here we focus on the physical properties and mechanics of the active matter systems. We model active particles using the active Brownian particle (ABP) model that is the simplest model that captures the essential physics, where a particle translates with a swim speed U0 in a direction q for a characteristic reorientation time \tτR; the average length they move between each reorientation is called the run, or persistence, length ℓ = U0τR. Owing to this persistent swimming, the ABPs distribute non-homogenously near surfaces, accumulating at no-flux boundaries leading to a concentration boundary layer near solid surfaces. Active particles often have an effective size—their run length—which can be much larger than their geometric size such that they experience confinement in geometries whose size is on the order of the run length. Active systems are inherently far from equilibrium, and we cannot appeal to properties of equilibrium thermodynamic such as the chemical potential to predict the partitioning. Fortunately, active particles are still subject to the laws of mechanics, and in this work, we present a simple macroscopic balance that allows one to predict behavior without detailed calculations. We predict the attractive force between two parallel plates in a reservoir (also called the Casimir effect) and find that the average concentration between the plates equals that in the bulk reservoir independent of the degree of confinement (ratio of run length to the spacing between the plates). We then examine the confinement effects in a channel geometry, where the behavior is fundamentally different, and the average concentration grows linearly with the degree of confinement. The understanding of these fundamental geometries motivated us to look into more complex geometries such as porous media. Based on dimensional analysis and our predictive model, we explain the transient behavior and steady-state partitioning of active particles between a fluid reservoir and a porous medium. Lastly, we discuss the hindered diffusion in periodic porous media and how the diffusion depends not only on the porosity of the medium but also on the degree of confinement. We believe that utilizing the insights in effects of confinement for these fundamental geometries and the porous media will be valuable in designing optimal structures for enhancing or isolating active particles.
", "doi": "10.7907/avfw-fh81", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14207", "collection": "thesis", "collection_id": "14207", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312021-044610797", "primary_object_url": { "basename": "Thesis_CharanSophia_2021.pdf", "content": "final", "filesize": 50382298, "license": "other", "mime_type": "application/pdf", "url": "/14207/1/Thesis_CharanSophia_2021.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Secondary Organic Aerosol Formation from Volatile Chemical Products: Understanding Aerosol Yields and Dynamics", "author": [ { "family_name": "Charan", "given_name": "Sophia Mohini", "orcid": "0000-0002-2023-6403", "clpid": "Charan-Sophia-Mohini" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" }, { "family_name": "Brady", "given_name": "John F.", "orcid": "0000-0001-5817-9128", "clpid": "Brady-J-F" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Particulate matter impacts public health and climate. A major component of small particulate matter, called secondary organic aerosol (SOA), is formed from the condensation of the oxidation products of organic compounds emitted into the atmosphere in the gas phase. Recent analysis suggests that volatile chemical products are responsible for a large fraction of the particulate matter formed from petroleum sources: perhaps more than motor vehicles. This is especially the case in urban areas, which have significant air pollution burdens.
\r\n \r\nUnderstanding exactly which precursors are responsible for this large SOA formation and under which conditions is difficult: for each compound, different chemical pathways dominate and even similar molecules can form vastly varied amounts of aerosol. Even if one could study every compound, extrapolating data to the atmosphere is non-trivial. SOA formation is principally understood through laboratory chamber studies, but these studies require a rigorous, quantitative grasp of chamber phenomena to meaningfully interpret the results.
\r\n \r\nIn this dissertation, computational simulations of environmental chambers illuminate the physico-chemical processes that occur within a chamber and the manner in which these processes interact, in order to help extrapolate data to real-world conditions. In particular, the contribution of particle charge to the rate of particle-wall deposition within environmental chambers is investigated.
\r\n\r\nWith this understanding, the amount of aerosol formed per precursor emitted, called the secondary organic aerosol yield, is investigated for benzyl alcohol and decamethylcylopentasiloxane (D5). At atmospherically relevant concentrations, benzyl alcohol and D5 have disparate SOA mass yields: as much as 100% for benzyl alcohol and ~1% for D5. Both of these findings differ from what was previously modeled and measured, indicating the importance of performing experiments on the compounds of interest and evaluating the oxidation products under atmospherically relevant conditions.
", "doi": "10.7907/yvj9-fv16", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13964", "collection": "thesis", "collection_id": "13964", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09232020-234052730", "primary_object_url": { "basename": "Kempler _ Thesis _ Revised2.pdf", "content": "final", "filesize": 19760134, "license": "other", "mime_type": "application/pdf", "url": "/13964/73/Kempler _ Thesis _ Revised2.pdf", "version": "v17.0.0" }, "type": "thesis", "title": "High-Aspect Ratio Structures in Light-Absorbers and Electrocatalysts for Solar Fuels Devices", "author": [ { "family_name": "Kempler", "given_name": "Paul Andrew", "orcid": "0000-0003-3909-1790", "clpid": "Kempler-Paul-Andrew" } ], "thesis_advisor": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "thesis_committee": [ { "family_name": "Davis", "given_name": "Mark E.", "orcid": "0000-0001-8294-1477", "clpid": "Davis-M-E" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Giapis", "given_name": "Konstantinos P.", "orcid": "0000-0002-7393-298X", "clpid": "Giapis-K-P" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Solar fuels devices produce hydrogen fuel from water and sunlight and address a critical societal need for inexpensive, long-duration energy storage. Such devices are prepared from combinations of light-absorbing semiconductors and catalysts to sunlight to drive thermodynamically uphill reactions. This dissertation puts forth strategies for controlling the three-dimensional structure of semiconductors, electrocatalysts, and the film of gas bubbles evolved on the top and bottom of a solar fuels device. High-aspect ratio features led to unexpected effects in semiconductor/electrocatalyst assemblies. Optical losses were decoupled from the mass-loading of cobalt phosphide and copper electrocatalysts integrated onto silicon microwire photocathodes for the photoelectrochemical generation of hydrogen and hydrocarbons, respectively. Anti-reflective silicon microcone arrays were patterned with continuous films of Pt or CoP particles with minimal reflection losses due to the catalyst films. Transparent metal films were prepared from nanostructured metal phosphides, a class of earth-abundant hydrogen evolution catalysts. Silicon microwire array (photo)electrode surfaces were used to force bubbles away from electrocatalyst surfaces, even when oriented against gravity, leading to sustained operation in the absence of external convection.
", "doi": "10.7907/xpty-9891", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13968", "collection": "thesis", "collection_id": "13968", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09272020-215437294", "type": "thesis", "title": "Nanometer-sized Aerosol Particles in the Atmosphere: Measurement, Analysis, and Impact", "author": [ { "family_name": "Kong", "given_name": "Weimeng (Stephanie)", "orcid": "0000-0002-9432-2857", "clpid": "Kong-Weimeng-Stephanie" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "New particle formation (NPF) from gaseous precursor vapors is frequently observed in the ambient environment and contributes to a major source of global cloud condensation nuclei (CCN). The survival and CCN activation of newly formed particles are highly dependent on particle growth below 10 nm. Characterizing and understanding nanoparticle early growth will therefore help to quantify the impact of NPF on cloud reflectivity and global energy budget. In this work, I first present a recently developed instrument, the Caltech nano-Scanning Electrical Mobility Spectrometer (nSEMS), which consists of a charge conditioner, a novel differential mobility analyzer (DMA), and a two-stage condensation particle counter (CPC). This new design, coupled with a data inversion method that combines empirical calibration and COMSOL simulation, can help to measure nanoparticle size distributions from 1.5 nm to 25 nm more accurately. This instrument was employed in the experiments conducted in the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at the European Organization for Nuclear Research (CERN) to better understand NPF, particle growth and survival. Multiple experimental parameters were varied to study the influence of different highly oxygenated molecules (HOMs) and inorganic trace gases, such as ammonia and nitrogen oxides on particle early growth. Experiment results have suggested a novel mechanism that may help to explain nanoparticle formation and growth in highly polluted urban environments or in the cold free troposphere. In as little as a few minutes, freshly nucleated particles as small as 2 nanometers in diameter can grow very rapidly due to simultaneous condensation of nitric acid and ammonia. This can help them to survive through the so-called \"valley of death\" where they would otherwise be lost to larger particles, and instead allow them to grow to sizes where they are less vulnerable to loss and can continue on to sizes where they influence local air quality or climate. Further, the laboratory results of nanoparticle growth were incorporated into the Global Model of Aerosol Processes (GLOMAP) model to study the impact of this extremely rapid growth on the global CCN budget. Having realized the importance of conducting well-controlled chamber experiments and of using chamber experimental data, we established an online data infrastructure, the Index of Chamber Atmospheric Research in the United States (ICARUS), for storing, sharing, and using chamber data. A combined effort of the described works contributes to better measuring the size distribution of nanoparticles and to understanding their impact on global climate.
", "doi": "10.7907/893j-7x60", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:14008", "collection": "thesis", "collection_id": "14008", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12022020-190300132", "primary_object_url": { "basename": "Messinger_Thesis_Final.pdf", "content": "final", "filesize": 2576650, "license": "other", "mime_type": "application/pdf", "url": "/14008/1/Messinger_Thesis_Final.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Spectroscopy and Kinetics of Atmospheric and Astrochemical Reactions", "author": [ { "family_name": "Messinger", "given_name": "Joseph Peter Herman", "orcid": "0000-0001-7305-3945", "clpid": "Messinger-Joseph-Peter-Herman" } ], "thesis_advisor": [ { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The reactions between reactive radicals and other neutral compounds have long been known to be important in atmospheric chemistry and astrochemistry. This work uses pulsed-laser photolysis cavity ringdown spectroscopy and laser-induced fluorescence to measure the rate constants and branching ratios of chemical reactions over a wide range of temperatures and pressures relevant to both polluted atmospheres, and the interstellar medium. This includes studying the OH + NO\u2082 reaction in the 253 \u2013 333 K range, the reaction of CN with benzene (C\u2086H\u2086) and toluene (C\u2087H\u2088) down to 16 K, and the OH + CO reaction down to 30 K.
", "doi": "10.7907/ak7w-w439", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:14221", "collection": "thesis", "collection_id": "14221", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012021-172201123", "primary_object_url": { "basename": "Allen_Hannah_2021.pdf", "content": "final", "filesize": 8409021, "license": "other", "mime_type": "application/pdf", "url": "/14221/2/Allen_Hannah_2021.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Constraining the Formation and Fate of Hydroperoxides in the Remote Atmosphere", "author": [ { "family_name": "Allen", "given_name": "Hannah Marie", "orcid": "0000-0002-4218-5133", "clpid": "Allen-Hannah-Marie" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Okumura", "given_name": "Mitchio", "orcid": "0000-0001-6874-1137", "clpid": "Okumura-M" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Atmospheric hydroperoxides form as second generation products in the atmospheric oxidation of many volatile organic compounds (VOCs) during reactions of these VOCs with OH and HO2 (i.e. HOx), where HOx are among the atmosphere's main oxidants and thus drivers of the majority of atmospheric chemistry. Once formed, the lifetime and ultimate fate of hydroperoxides are set by a variety of potential chemical and physical pathways that have different impacts on the atmosphere's oxidizing capacity, including either recycling HOx or removing HOx. This dissertation explores the role of hydroperoxides with several different structures through field and laboratory studies using CF3O- chemical ionization mass spectrometry (CIMS) to understand the role of these hydroperoxides in the oxidation chemistry of the remote atmosphere.
\r\n\r\nHydrogen peroxide (H2O2) and methyl hydroperoxide (MHP, CH3OOH) are two of the most abundant hydroperoxides found in oceanic environments. Both hydroperoxides were measured using time of flight and tandem quadrupole CIMS aboard the NASA DC-8 aircraft during the Atmospheric Tomography Mission, enabling a seasonal investigation into their global distribution with near pole-to-pole coverage across the Pacific and Atlantic Oceans and ranging in altitude from the marine boundary layer to the upper troposphere and lower stratosphere. Hydroxymethyl hydroperoxide (HMHP, HOCH2OOH) and isoprene hydroxy hydroperoxides (ISOPOOH, HOC5H8OOH) are organic hydroperoxides derived from the oxidation of isoprene, one of the dominant biogenic VOCs in forested environments. The loss of HMHP from the atmosphere via reaction with OH is investigated in the laboratory using time of flight CIMS and laser induced fluorescence along with theoretical chemical modeling methods. To better distinguish the varying roles of structurally complex hydroperoxides, a novel field-deployable gas chromatograph integrated with a high resolution time of flight CIMS is developed that sensitively detects hydroperoxides along with a number of other oxidation products. This instrument is deployed at a rural forested site in northern Michigan during the PROPHET field campaign to probe the relative contribution of different ISOPOOH isomers to the oxidation pathways of isoprene.
", "doi": "10.7907/1108-c936", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13763", "collection": "thesis", "collection_id": "13763", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012020-155204817", "primary_object_url": { "basename": "rooney_brigitte_2020_thesis.pdf", "content": "final", "filesize": 4866331, "license": "other", "mime_type": "application/pdf", "url": "/13763/1/rooney_brigitte_2020_thesis.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Modeling the Impact of Biomass Combustion on Atmospheric Aerosol", "author": [ { "family_name": "Rooney", "given_name": "Brigitte Lee", "orcid": "0000-0002-9725-9080", "clpid": "Rooney-Brigitte-Lee" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Wang", "given_name": "Yuan", "clpid": "Wang-Yuan" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Biomass burning is a significant source of atmospheric particulate matter less than 2.5 micrometers in diameter (PM2.5) and encompasses a variety of activities, fuels, and emissions profiles. A significant portion of the world population relies on solid biofuels for cooking and other household activities. Residential use of solid biofuels can have negative impacts on human health, particularly in southeast Asia, and contribute to ambient air quality. In addition, wildfires are of increasing concern as climate changes and human activity expands further into the wildland-urban interface. Understanding the contributions of biomass combustion to air quality is critical for creating mitigation strategies.
\r\n\r\nIn this work, the impact of biomass burning on air quality is examined using numerical and observational methods. The Community Multiscale Air Quality modeling system (CMAQ) and the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) are used to study two biomass burning scenarios: the combustion of solid biofuels for cooking in rural India and the November 2018 Camp Fire in northern California. Model simulations are combined with surface and satellite observational data to evaluate their performance as well as their applicability to health and economic impact assessment studies. Additionally, discrepancies in methods used in laboratory experiments and field studies of cookstove emissions are investigated. Contributions of cookstove and wildfire emissions to PM2.5 are estimated, and climate and health co-benefits of residential solid biofuel use is assessed. This thesis strives to expand the current understanding of sources of PM2.5 and provide a base for future computational studies of biomass burning impacts on air quality, climate, and human health.
", "doi": "10.7907/adpa-0947", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:11313", "collection": "thesis", "collection_id": "11313", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12122018-171618053", "type": "thesis", "title": "Intramolecular Hydrogen-shift Reactions of Peroxy Radicals", "author": [ { "family_name": "Praske", "given_name": "Eric", "orcid": "0000-0001-7169-4423", "clpid": "Praske-Eric" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Straight chain alkanes with more than five carbons, emitted in cities due to incomplete combustion and fuel evaporation, undergo atmospheric gas-phase oxidation with the hydroxyl radical to produce alkyl radicals. These alkyl radicals subsequently add O2, leading to the formation of peroxy radicals. Following further reaction of these radicals in urban areas, hydroxy-substituted peroxy radicals are formed. Previously, the fate of these peroxy radicals was assumed to be dominated by reaction with nitric oxide, a common air pollutant. Computational and experimental investigations of the oxidation mechanism of 2-hexanol, however, demonstrate that hydrogens \u03b1 to the hydroxy group exhibit a significantly reduced energetic barrier toward intramolecular hydrogen shifts to the peroxy radical. The barrier reduction for these hydrogen shift reactions results in rate constants that are orders of magnitude larger than for alkyl hydrogens that lack \u03b1 substitution. Due to significant reductions of nitric oxide emissions in North America, these rate constants are sufficiently large to suggest that this chemistry is competitive even in large cities, particularly during warm summer days. Gas-phase alkyl hydroperoxides, a class of compounds previously expected to exist in negligible quantities in cities, are major products of this chemistry.
\r\n\r\nFurther oxidation of alkyl hydroperoxides leads to the formation of hydroperoxy-substituted peroxy radicals. The chemistry of such peroxy radicals is evaluated through the oxidation of 2-hydroperoxy-2-methylpentane. Experimental observations confirm the previously reported computational result that these peroxy radicals rapidly isomerize by intramolecular hydrogen shift of the hydroperoxide hydrogen. This isomerization occurs on timescales that are much faster than those of bimolecular reaction in essentially all regions of the troposphere. As a consequence of the isomerization, one peroxy radical isomer produced in the oxidation of 2-hydroperoxy-2-methylpentane exhibits an \u03b1 hydroperoxide hydrogen shift. This reaction rate constant is similar to that reported for the \u03b1 hydroxy hydrogen shift in the 2-hexanol system.
\r\n\r\nAlkoxy radicals produced in the oxidation of 2-hydroperoxy-2-methylpentane are similarly shown to undergo a very rapid hydrogen shift of the hydroperoxide hydrogen. One of these shifts results in a peroxy radical that exhibits an \u03b1 hydroxy hydrogen shift. Thus, the rapid scrambling of hydroperoxy-subsituted alkoxy and peroxy radicals is a key process that can enable additional unimolecular pathways that are otherwise inaccessible. This chemistry has the potential to introduce significant mechanistic complexity and, due to the rapid nature of the reactions, cannot be neglected even under typical \"high NO\" conditions employed in chamber studies.
", "doi": "10.7907/KBX8-H010", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11720", "collection": "thesis", "collection_id": "11720", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06072019-161940566", "primary_object_url": { "basename": "grantz_amanda_2019_thesis.pdf", "content": "final", "filesize": 13534786, "license": "other", "mime_type": "application/pdf", "url": "/11720/1/grantz_amanda_2019_thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Aerosol Particle Measurements: Strategies for Health-Relevant Data Collection and Analysis", "author": [ { "family_name": "Grantz Pansing", "given_name": "Amanda", "clpid": "Grantz-Pansing-Amanda" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Davis", "given_name": "Mark E.", "clpid": "Davis-M-E" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Particulate matter (PM) is an important component of outdoor and indoor air pollution that can cause significant harm to human health. The present work, organized into two parts, introduces strategies for optimizing the collection and analysis of airborne particle measurements to inform PM health-effect research.
\r\n\r\nPart I focuses on the fundamental aerosol data analysis task of interpreting indirect measurements of particle size to reveal the distribution of sizes of particles in a sampled aerosol. An approach to this aerosol data inversion problem is developed that shows improved particle size distribution recovery compared to other common approaches described in the literature. This inverse solution method incorporates cubic spline interpolation to represent the particle size distribution within a discrete linear model of the inverse problem while placing no constraints on the number or spacing of solution points. The inverse problem setup can then interface with three established numerical methods for solution computation. The accuracy of this procedure is demonstrated through analysis of test-case data for differential mobility analyzer systems. Source code and supporting documentation are also provided to encourage researchers to use and adapt this inversion algorithm for analyzing data collected from existing as well as potential future measurement systems.
\r\n\r\nPart II of this work focuses on the retrieval of health-relevant information from aerosol particle measurement data. The inversion analysis introduced in Part I is incorporated into an extended analysis procedure for evaluating the metrics of PM exposure and respiratory dose that can be obtained from different measurement systems. Applying this evaluation procedure to a range of existing and potential future measurement techniques reveals that full characterization of particle size distributions need not be time and resource intensive and should be pursued for the great benefits this information would provide to health studies. Not only can size distribution information permit lung tissue dose estimates through a set of relatively simple calculations, but a single set of size distribution data can be analyzed and reanalyzed to provide dose estimates for human populations of interest by applying the appropriate respiratory tract deposition profiles. The measurement evaluation procedure developed here reveals target criteria for the particle characterization necessary to provide sufficient exposure and dose information for health studies. The intent is not to eliminate the current measurements and standards, but to help direct future developments in health-related aerosol particle measurement design.
", "doi": "10.7907/Y730-W245", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11539", "collection": "thesis", "collection_id": "11539", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05232019-231457899", "primary_object_url": { "basename": "Huang_Yuanlong_2019.pdf", "content": "final", "filesize": 17832600, "license": "other", "mime_type": "application/pdf", "url": "/11539/1/Huang_Yuanlong_2019.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Development of Methods to Study Secondary Organic Aerosol", "author": [ { "family_name": "Huang", "given_name": "Yuanlong", "orcid": "0000-0002-6726-8904", "clpid": "Huang-Yuanlong" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Secondary organic aerosol (SOA) in the atmosphere contributes significantly to air pollution and has profound impacts on regional and global climate change, as well as human health. SOA, as opposed to directly emitted particles, refers to those particles formed from oxidation of gas-phase compounds followed by nucleation and/or gas-particle partitioning, as well as those modified by gas-phase oxidants (e.g., O3, OH radical, and NO3 radical) through heterogeneous reactions within their lifetime in the atmosphere. Investigations of SOA formation in the laboratory have been carried out in batch reactors (e.g., environmental smog chambers) and continuous flow reactors (e.g., oxidation flow reactors). Compared with the real atmosphere, the reactors in the laboratory have boundaries and defined residence times under different operation conditions. To better constrain the experimental results and derive reliable parameters for aerosol models (e.g., yields of volatile organic compounds), a full understanding of the role of the reactors on the gas-phase components and suspended particles is needed.
\r\n \r\nIn this thesis research, a number of studies were carried out to understand the role of the reactor itself on the behavior of SOA-forming systems. This includes the effect of the Teflon-walled Caltech Environmental Chamber on vapor molecules and characterization of the newly-built Caltech PhotoOxidation Flow Tube reactor (CPOT) for atmospheric chemistry studies.
\r\n \r\nVapor-wall interactions in Teflon-walled environmental chambers have been studied; however, conflicting results existed in the literature concerning the basic timescales of vapor-wall loss in environmental chambers. The competition between vapor-particle and vapor-wall interactions determines the fate of vapor molecules in the reactor. A unified theory and empirical equations have been developed in this thesis to explain the observed vapor-wall interaction timescales. About 100 compounds have been studied to verify this theory. In characterizing the flow reactor performance, computational fluid dynamics (CFD) simulations have been combined with residence time distribution (RTD) experiments, revealing, among others, the importance of the inlet design of the reactor and the effect of temperature gradients on radial mixing in the reactor. An axial-dispersed plug flow reactor (AD-PFR) model framework was developed as a basis on which to simulate photochemistry occurring in the CPOT. An analytical solution for the cumulative RTD, which uses data during the transition period to a steady state, can be applied to diagnose the dispersion condition inside the flow rector.
\r\n \r\nSince SOA formation involves interactions among gas-phase molecules, particle surfaces, and particle bulk phases, a state-of-the-art experimental technique (field-induced droplet ionization mass spectrometry, FIDI-MS) and a comprehensive model coupling gas-surface-aqueous multiphase transport and chemical reactions have been applied to investigate the gas-phase OH-initiated oxidation of pinonic acid (PA) at the air-water interface. The interfacial oxidation mechanism has been found to differ from that of homogeneous reactions, and the kinetics depend on both OH diffusion from gas-phase to the interface and aqueous-phase reaction of pinonic acid + OH. The model calculation shows that, under typical ambient OH levels, PA is oxidized exclusively at the air-water interface of droplets with a diameter of 5 \u00b5m, demonstrating the critical importance of air-water interfacial chemistry in determining the fate of surface-active species.
", "doi": "10.7907/783S-K686", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:10989", "collection": "thesis", "collection_id": "10989", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312018-154833107", "primary_object_url": { "basename": "caltech-thesis-zhang-xiyue-final.pdf", "content": "final", "filesize": 5643782, "license": "other", "mime_type": "application/pdf", "url": "/10989/2/caltech-thesis-zhang-xiyue-final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Dynamics of Resolved Polar Clouds", "author": [ { "family_name": "Zhang", "given_name": "Xiyue", "orcid": "0000-0002-6031-7830", "clpid": "Zhang-Xiyue" } ], "thesis_advisor": [ { "family_name": "Schneider", "given_name": "Tapio", "orcid": "0000-0001-5687-2287", "clpid": "Schneider-T" } ], "thesis_committee": [ { "family_name": "Bordoni", "given_name": "Simona", "orcid": "0000-0003-4771-3350", "clpid": "Bordoni-S" }, { "family_name": "Thompson", "given_name": "Andrew F.", "orcid": "0000-0003-0322-4811", "clpid": "Thompson-A-F" }, { "family_name": "Teixeira", "given_name": "Joao", "clpid": "Teixeira-Joao" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Schneider", "given_name": "Tapio", "orcid": "0000-0001-5687-2287", "clpid": "Schneider-T" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The polar regions have been experiencing rapid warming and ice loss as greenhouse gas concentrations have risen. The projected warming in the Arctic varies significantly across climate models, part of which is attributed to polar cloud feedbacks. This thesis addresses the question of what drives the changes in polar clouds as the climate warms, using a large eddy simulation (LES) model. LES is a powerful high-resolution model that resolves the most energetic turbulence relevant for clouds. First, we focus on the Arctic boundary layer clouds through three observation based case studies. The cloud and boundary layer characteristics simulated by the LES agree reasonably well with observations and model intercomparisons. We found that during polar night over sea ice, cloud water path increases with temperature and free-tropospheric relative humidity, but it decreases with inversion strength across the cloud top. Most of these changes can be explained by a mixed-layer model. The strength of the estimated positive cloud longwave feedback largely depends on the cloud top inversion strength. Next, we extend the LES domain to cover the entire polar troposphere, and use output from an idealized GCM as forcing to drive the LES. This novel framework allows changes in the large-scale circulation to be parameterized in the LES. The simulated seasonal cycle of liquid clouds resembles observations. In a warmer climate, there is a significant decrease of the low-level liquid clouds during summer and autumn. In spring and winter, liquid clouds increase at all levels. Both the liquid and ice cloud tops rise as the climate warms. Offline radiative transfer calculations estimate a positive cloud feedback that is dominated by longwave feedback.\r\n", "doi": "10.7907/69E7-0Q10", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10989", "collection": "thesis", "collection_id": "10989", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312018-154833107", "primary_object_url": { "basename": "caltech-thesis-zhang-xiyue-final.pdf", "content": "final", "filesize": 5643782, "license": "other", "mime_type": "application/pdf", "url": "/10989/2/caltech-thesis-zhang-xiyue-final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Dynamics of Resolved Polar Clouds", "author": [ { "family_name": "Zhang", "given_name": "Xiyue", "orcid": "0000-0002-6031-7830", "clpid": "Zhang-Xiyue" } ], "thesis_advisor": [ { "family_name": "Schneider", "given_name": "Tapio", "orcid": "0000-0001-5687-2287", "clpid": "Schneider-T" } ], "thesis_committee": [ { "family_name": "Bordoni", "given_name": "Simona", "orcid": "0000-0003-4771-3350", "clpid": "Bordoni-S" }, { "family_name": "Thompson", "given_name": "Andrew F.", "orcid": "0000-0003-0322-4811", "clpid": "Thompson-A-F" }, { "family_name": "Teixeira", "given_name": "Joao", "clpid": "Teixeira-Joao" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Schneider", "given_name": "Tapio", "orcid": "0000-0001-5687-2287", "clpid": "Schneider-T" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The polar regions have been experiencing rapid warming and ice loss as greenhouse gas concentrations have risen. The projected warming in the Arctic varies significantly across climate models, part of which is attributed to polar cloud feedbacks. This thesis addresses the question of what drives the changes in polar clouds as the climate warms, using a large eddy simulation (LES) model. LES is a powerful high-resolution model that resolves the most energetic turbulence relevant for clouds. First, we focus on the Arctic boundary layer clouds through three observation based case studies. The cloud and boundary layer characteristics simulated by the LES agree reasonably well with observations and model intercomparisons. We found that during polar night over sea ice, cloud water path increases with temperature and free-tropospheric relative humidity, but it decreases with inversion strength across the cloud top. Most of these changes can be explained by a mixed-layer model. The strength of the estimated positive cloud longwave feedback largely depends on the cloud top inversion strength. Next, we extend the LES domain to cover the entire polar troposphere, and use output from an idealized GCM as forcing to drive the LES. This novel framework allows changes in the large-scale circulation to be parameterized in the LES. The simulated seasonal cycle of liquid clouds resembles observations. In a warmer climate, there is a significant decrease of the low-level liquid clouds during summer and autumn. In spring and winter, liquid clouds increase at all levels. Both the liquid and ice cloud tops rise as the climate warms. Offline radiative transfer calculations estimate a positive cloud feedback that is dominated by longwave feedback.\r\n", "doi": "10.7907/69E7-0Q10", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10454", "collection": "thesis", "collection_id": "10454", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09252017-114900745", "type": "thesis", "title": "The Study of the Stepwise Hydroxyl Radical-Mediated Oxidation of Alkyl Surfactants at the Air-Water Interface", "author": [ { "family_name": "Barraza", "given_name": "Kevin Mitchell", "orcid": "0000-0003-1849-5219", "clpid": "Barraza-Kevin-Mitchell" } ], "thesis_advisor": [ { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" } ], "thesis_committee": [ { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Dervan", "given_name": "Peter B.", "clpid": "Dervan-P-B" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis presents work on the heterogeneous chemistry of surfactant monolayers adsorbed at the air-water interface with gas phase hydroxyl radicals (OH). A novel hydroxyl radical source utilizing a low-temperature plasma known as the dielectric barrier discharge source (DBDS) is designed, characterized, and implemented as a high concentration OH generator (approximately 1000 fold higher than ambient conditions) in these experiments. Millimeter-sized water droplets containing a monolayer of surface-adsorbed species are exposed to this OH source until a designated level of oxidation. Field-induced droplet ionization mass spectrometry (FIDI-MS), which has been previously proven to be a surface-selective ionization technique, is used as an analytical method to determine the identity and relative quantity of oxidation products at the interface by sampling progeny droplets expelled upon the application of a pulsed electric field. Chapter 2 establishes the utility of the DBDS and FIDI-MS setup by oxidizing the 12-carbon n-alkyl surfactant dodecyltrimethylammonium (DTA+). Mechanistic details can be determined through the evolution of high mass oxidation products through a nearly complete conversion of the parent monolayer. Carbonyl, hydroxyl, peroxyl, and small amounts of fragmentation products can be discerned from the collision-induced dissociation mass spectra and through hydrogen-deuterium exchange experiments. Psuedo-first order kinetics can also be observed in this system, suggesting a Langmuir-Hinshelwood mechanism of OH-initiated oxidation. Chapter 3 extends the study of oxidation of hydrocarbon surfactants by looking at neighbor chain competition among a bis-quaternary ammonium gemini surfactants, a species that contains two long alkyl chains. Specifically, the experiment assesses the ability of two non-identical alkyl chains to compete with each other for the impinging gas phase hydroxyl radical. The increased reactivity of singly oxidized chains is evaluated by the oxidation of a gemini surfactant parent with identical alkyl chains. Chapter 4 investigates the oxidation of \u03b1,\u03c9-surfactants, those that contain polar functional group separated by methylene spacers, discussing deviations of this class of surfactants with those that contain only one head group (i.e. DTA+). Chapter 5 demonstrates the DBDS and FIDI-MS system for use as a peptide footprinting technique for the amphiphilic species substance P. Localization of the site of oxidation can be done through FIDI-MS/MS analysis.
", "doi": "10.7907/Z9BG2M5K", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10949", "collection": "thesis", "collection_id": "10949", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05272018-093411980", "primary_object_url": { "basename": "Mai_Huajun_2018.pdf", "content": "final", "filesize": 56276256, "license": "other", "mime_type": "application/pdf", "url": "/10949/1/Mai_Huajun_2018.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Scanning Electrical Mobility Methods for Aerosol Characterization", "author": [ { "family_name": "Mai", "given_name": "Huajun", "orcid": "0000-0002-0616-1986", "clpid": "Mai-Huajun" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The scanning electrical mobility measurement is the most common tool used to characterize the size distribution of fine particles in the atmosphere. This thesis develops the methods for retrieving the particle size distribution from scanning electrical mobility measurement data for two systems: (1) the scanning electrical mobility spectrometer (SEMS; also known as the scanning mobility particle sizer, SMPS), which measures particle size distribution ranging from 15 - 1000 nm; (2) the scanning radial opposed migration ion and aerosol classifier (ROMIAC) system, which uses a two-stage condensation particle counter as particle detector to complete the 1 - 20 nm particle size distribution measurements.
\r\n\r\nSEMS / SMPS data have traditionally been inverted to determine the particle size distribution by solving a Fredholm integral equation in which the kernel function is based upon constant-voltage operation of the mobility classifier. The viscous boundary layer within the classifier renders that model invalid. This thesis determines, for the first time, the transfer function for a real differential mobility analyzer (DMA) that is operated in the scanning mode. The flow and electric fields within the instrument were obtained by finite element simulations taking into account its detailed geometry. Brownian dynamics simulations were then used to simulate diffusive particle trajectories within the instrument as the voltage was scanned. There results were coupled with empirically-derived response-time functions for the condensation particle counter that serves as a detector in the SEMS / SMPS to obtain integrated system transfer function that substantially improve the fidelity of the SEMS / SMPS data inversion.
\r\n\r\nThis approach was also applied to adaptation of the radial opposed migration ion/aerosol classifier (ROMIAC) for scanning-mode operation. The transfer function obtained through simulation of the scanning ROMIAC was used in the experimental validation of this new measurement method. This new instrument was then used to measure wall loss rates for 1.6 nm to 20 nm particles in the Caltech environmental chamber.
", "doi": "10.7907/9D4H-QS44", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10544", "collection": "thesis", "collection_id": "10544", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10252017-021526235", "primary_object_url": { "basename": "kmarshall-thesis-final-oneside.pdf", "content": "final", "filesize": 37536636, "license": "other", "mime_type": "application/pdf", "url": "/10544/1/kmarshall-thesis-final-oneside.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "The Hydrodynamics of Active Particles Inside of a Porous Container and the Galerkin Boundary Element Discretization of Stokes Flow", "author": [ { "family_name": "Marshall", "given_name": "Kevin James", "orcid": "0000-0001-6025-7674", "clpid": "Marshall-Kevin-James" } ], "thesis_advisor": [ { "family_name": "Brady", "given_name": "John F.", "clpid": "Brady-J-F" } ], "thesis_committee": [ { "family_name": "Brady", "given_name": "John F.", "clpid": "Brady-J-F" }, { "family_name": "Barr", "given_name": "Alan H.", "clpid": "Barr-A-H" }, { "family_name": "Kornfield", "given_name": "Julia A.", "clpid": "Kornfield-J-A" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "In this thesis I formulate and present a novel and new framework for simulating the dynamics of arbitrarily shaped active or passive particles immersed in a Stokesian fluid and evolving under confinement by a porous container or in free space. I use a completed double layer boundary integral equation to model the particle's dynamics and combine this with a new formulation that uses a second kind integral equation for describing the motion of the porous container. This newly formulated porous container model permits fluid to pass through the container's surface at a velocity in proportion to a discontinuous jump in stress across the container's surface. This jump in stress is induced by the active particle's motion. The proposed porous container model is general in the sense that it allows fluid to pass through the membrane with finite tangential and normal velocity components. I obtain the exact analytical solution to this model when the active particle and porous container are perfectly concentric. In addition, I numerically solve this system of boundary integral equations for arbitrary particle positions, and fully characterize the particle and container dynamics by performing a vast number of trajectory studies. Both the container and particle are seen to move in complicated ways owing to their self and pairwise hydrodynamic interactions. This system is studied over a vast parameter space, for multiple container to particle size ratios, multiple types of active particles, and various permeability parameterizations. This coupled set of particle and container boundary integral equations is discretized using a novel interpretation and new extension of the Galerkin Boundary Element discretization to multi-body particle systems in Stokes flow. I also implement and extend an h-adaptive conformal mesh refinement algorithm to accurately resolve near-contact particle and container interactions. In addition, I perform all Galerkin BEM calculations on CUDA enabled GPUs, allowing for these simulations to be run on modern desktop computers in seconds. I combine all of these techniques in a modern C++ Galerkin Boundary Element Method computational framework called GPUGBEM.
", "doi": "10.7907/Z9MP51G8", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10137", "collection": "thesis", "collection_id": "10137", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04142017-135033314", "primary_object_url": { "basename": "Hedelius_Jacob_2017_fullthesis.pdf", "content": "final", "filesize": 16777443, "license": "other", "mime_type": "application/pdf", "url": "/10137/1/Hedelius_Jacob_2017_fullthesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "What Can We Infer About the Atmospheric Composition Within the South Coast Air Basin from Remote Sensing?", "author": [ { "family_name": "Hedelius", "given_name": "Jacob K.", "orcid": "0000-0003-2025-7519", "clpid": "Hedelius-Jacob-K" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "To observe a change in a gas (e.g., CO2) flux from an area, the change must exceed the error of the flux estimate. Changing bias could be misinterpreted as a change in flux, and should be avoided. Errors can arise in column CO2 (XCO2) retrievals, in mis-interpreting XCO2 variations, or in the models to estimate fluxes. My thesis work has focused on recognizing and quantifying these errors and biases.
\r\n\r\nThe most widely-used ground-based observations of XCO2 are from the Total Carbon Column Observing Network (TCCON), which uses observations from similar spectrometers at high (0.02 cm-1) resolution. Within the past 5 years there has been increased use of portable, lower resolution (0.5 cm-1) spectrometers for focused, short-term campaigns. This thesis discusses sources of errors and biases in retrievals from these lower resolution spectrometers.
\r\n\r\nPrevious error estimates for the TCCON were made by propagating various perturbations through the retrieval. These uncertainty estimates were about 0.2 % for CO2 and 0.4 % for CH4. A pair of portable 0.5 cm-1 resolution spectrometers were used to empirically diagnose the magnitude of bias among TCCON sites. Median estimates were about 0.1 %.
\r\n\r\nColumn measurements have increased in popularity within the last 15 years because of their reduced sensitivity to the dry mole fractions (DMF) of gases near the surface. However, in the presence of a sharp gradient between the atmospheric mixed layer (ML) and free troposphere rapid changes in terrain may cause the ML height above ground level and XCO2 to vary significantly over a small area. This explains ~20-36 % of the difference in XCO2 between 2 sites (Caltech and JPL) within 10 km of each other in the South Coast Air Basin (SoCAB).
\r\n\r\nDynamical models may have biases (e.g., in wind speed) compared to true atmospheric behavior. This may cause biases in flux estimates. An estimate of the SoCAB CO2 flux using readily available model data is higher than those reported by bottom-up methods, perhaps due to a high wind speed bias. The flux is also sensitive to sub-sampling, which highlights the need to filter out biased data and the benefits additional observations could provide.
\r\n\r\nCarbon dioxide is not the only radiative forcer---aerosols are the largest source of uncertainty on the global radiative forcing budget, and additional measurements may better constrain their impacts. Estimate of changes in aerosol optical depth (AOD) can be made using portable spectrometers. While these estimates are not highly accurate, they are a value-added product and may increase the understanding of atmospheric behavior.
", "doi": "10.7907/Z9862DGR", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10265", "collection": "thesis", "collection_id": "10265", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042017-134711204", "primary_object_url": { "basename": "teng-alexander-2017.pdf", "content": "final", "filesize": 24441892, "license": "other", "mime_type": "application/pdf", "url": "/10265/1/teng-alexander-2017.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Insights on the Formation and Fate of Organic Nitrates in the Atmosphere from Field and Laboratory Observations", "author": [ { "family_name": "Teng", "given_name": "Alexander Pai-Chung", "orcid": "0000-0002-6434-0501", "clpid": "Teng-Alexander-Pai-Chung" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Sander", "given_name": "Stanley P.", "clpid": "Sander-S-P" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Alkenes are oxidized rapidly in the atmosphere by addition of OH and subsequently O2, leading to the formation of peroxy radicals. These peroxy radicals react with NO to form organic nitrates through a minor radical-terminating branching pathway. Over large regions of the continental boundary layer, the formation of organic nitrates control tropospheric ozone and the lifetime of NOx. Laboratory investigations described herein show that the yield of nitrates through this pathway is larger than previously described for alkenes, and the yield increases with the number of heavy atoms. This result is used to interpret field observations taken over Houston in the summer of 2013. These measurements show that small alkenes still play a large role in ozone production more than a decade after they had been identified as a causal factor.\r\n\r\nIn further studies, measurements of isoprene hydroxy nitrates (ISOPN) and hydroperoxides, formed from the OH oxidation of isoprene, are used to diagnose the complexities of reversible O2 addition for allylic hydroxy isoprene radicals. It is shown that over most of the atmosphere, isoprene's peroxy radical isomers are in their equilibrium distribution. In this regime, hydroxy peroxy radical isomers comprise approximately 95% of the radical pool, a much higher fraction than in the nascent (kinetic) distribution. Intramolecular H-shift isomerization from the Z hydroxy peroxy radical isomers produced from OH addition to C4 is estimated to be 4s-1 at 297K. While the Z isomer is initially produced in low yield, it is continually reformed via decomposition of the hydroxy peroxy radicals. As a result, unimolecular chemistry from this isomer contributes as much as half of the atmospheric fate of the entire pool of peroxy radicals formed via addition of OH at C4. In contrast, unimolecular chemistry following OH addition at C1 is slower and less important. \r\n\r\nField observations of alkyl nitrates over the Southeastern United States during the summer over forested environments show that there are still gaps in our understanding of the organic nitrate budget. The formation of isoprene hydroxy nitrates (ISOPN) is shown to be a dominant NOx loss pathway during the day. ", "doi": "10.7907/Z9RV0KRJ", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10233", "collection": "thesis", "collection_id": "10233", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312017-144547085", "primary_object_url": { "basename": "Bates_Kelvin_2017.pdf", "content": "final", "filesize": 58551554, "license": "other", "mime_type": "application/pdf", "url": "/10233/103/Bates_Kelvin_2017.pdf", "version": "v23.0.0" }, "type": "thesis", "title": "Isoprene Oxidation Mechanisms and Secondary Organic Aerosol Formation Under HO2-Dominated Conditions", "author": [ { "family_name": "Bates", "given_name": "Kelvin Hamilton", "orcid": "0000-0001-7544-9580", "clpid": "Bates-Kelvin-Hamilton" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Stoltz", "given_name": "Brian M.", "clpid": "Stoltz-B-M" } ], "thesis_committee": [ { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Stoltz", "given_name": "Brian M.", "clpid": "Stoltz-B-M" }, { "family_name": "Grubbs", "given_name": "Robert H.", "clpid": "Grubbs-R-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Isoprene, a volatile hydrocarbon emitted by plants, represents the single most abundant source of non-methane organic carbon to the atmosphere. After its rapid oxidation by OH radicals in the troposphere, isoprene may follow any of a number of complex reaction mechanisms to form more highly functionalized products, depending in large part on the relative abundance of reactive radicals such as HO2 and NO; some of these products can be sufficiently water-soluble, non-volatile, and/or reactive to partition into atmospheric particles and contribute to the creation of secondary organic aerosol (SOA). In this work, I explore the gas-phase oxidation mechanisms and SOA formation potential of second- and later-generation products formed in the HO2-dominated reaction cascade, which predominates in remote regions and is estimated to account for over >40% of isoprene oxidation. Pure standards of significant isoprene products, such as isoprene epoxydiols (IEPOX) and C4 dihydroxycarbonyl compounds, are synthesized, and the rates and product yields of their gas-phase reactions with OH are measured by CF3O- chemical ionization mass spectrometry in environmental chamber experiments. Results are compared to field observations from the Southern Oxidant and Aerosol Study in the Southeastern United States, where significant concentrations of these compounds were detected, and are integrated into a global chemical transport model to investigate their effects throughout the atmosphere. Further, the results from these and other gas-phase kinetic and product studies are incorporated into an explicit isoprene oxidation mechanism, designed to simulate the effects of isoprene chemistry on oxidant concentrations and to produce accurate representations of products known to be involved in condensed phase processes, including IEPOX. Finally, additional chamber experiments with synthetic IEPOX and inorganic seed aerosol are performed to derive particle uptake coefficients and examine the effects of particle pH, liquid water content, and chemical composition on IEPOX-SOA formation, using aerosol mass spectrometry and differential mobility analysis. The gas- and particle-phase reaction rates and product yields reported herein, along with the explicit model, provide important constraints on the fate of isoprene-derived carbon in the atmosphere and on the influence the HO2-dominated isoprene oxidation pathway exerts on SOA and oxidant budgets.
", "doi": "10.7907/Z9930R6T", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:9971", "collection": "thesis", "collection_id": "9971", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11022016-133509841", "type": "thesis", "title": "Identifying Isoprene and Toluene Gas-Phase Oxidation Products to Better Constrain Ozone and Secondary Organic Aerosol Formation in the Atmosphere", "author": [ { "family_name": "Schwantes", "given_name": "Rebecca Helen", "orcid": "0000-0002-7095-3718", "clpid": "Schwantes-Rebecca-Helen" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Anthropogenic pollutants such as NOx interact with volatile organic compounds (VOCs) such as isoprene and toluene to produce ozone (O3) and oxidized low volatility compounds that are responsible for forming secondary organic aerosol (SOA). Understanding the processes that form O3 and SOA from VOCs is important for understanding climate interactions and air quality. Both O3 and SOA are harmful air pollutants. O3 directly contributes to warming while the influence of aerosols is far more complicated, but ultimately leads to regional cooling. Understanding the chemistry that produces O3 and SOA will help better predict how future regulations will influence climate and air quality. A series of experiments using the Caltech chamber facility were designed and performed to better understand the influence of isoprene and toluene gas-phase oxidation products on O3 and SOA formation.
\r\n\r\nFirst, in order to conduct experiments, the new Caltech chamber facility was characterized. Second, to understand the oxidation products from isoprene in the presence of anthropogenic pollutants such as NOx, a chemical ionization mass spectrometer (CIMS) was used to identify the gas-phase products from the oxidation of isoprene by the nitrate radical (NO3). First-generation nitrates were identified to be predominantly δ-nitrates while first-generation nitrates formed from OH oxidation of isoprene in the presence of NO are predominantly β-nitrates. This has important consequences for NOx recycling and O3 generation because these β- and δ-nitrates react with O3 and OH at different rates and form different products. Photooxidation products from nitrooxy hydroperoxide, a product from isoprene + NO3 oxidation (in the presence of hydroperoxy radical-HO2), were identified to be predominantly propanone nitrate and nitrooxy hydroxy epoxide. Nitrooxy hydroxy epoxide undergoes reactive uptake to seed aerosol similar to isoprene dihydroxy epoxide, suggesting it may be important for SOA formation.
\r\n\r\nLastly, first- and later-generation photooxoidation products from cresol and benzaldehyde oxidation were identified. Cresol and benzaldehyde are products from toluene OH oxidation. Low volatility ring-retaining products produced from cresol oxidation were detected in the gas phase by the CIMS and in the particle phase using offline direct analysis in real time mass spectrometry (DART-MS). Products detected included polyols such as dihydroxy, trihydroxy, tetrahydroxy, and pentahydroxy toluenes and benzoquinones such as hydroxy, dihydroxy, and trihydroxy methyl benzoquinones. These results suggest that even though the cresol pathway only contributes ∼20% to gas-phase toluene oxidation, products from the cresol channel potentially generate a significant fraction ( ∼20-40%) of toluene SOA.
", "doi": "10.7907/Z92805K8", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:9917", "collection": "thesis", "collection_id": "9917", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09062016-204048228", "type": "thesis", "title": "Development and Applications of Opposed Migration Aerosol Classifiers (OMACs)", "author": [ { "family_name": "Mui", "given_name": "Wilton", "orcid": "0000-0003-3065-1296", "clpid": "Mui-Wilton" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Particle electrical mobility classification has made important contributions in atmospheric and climate science, public health and welfare policy, and nanotechnology. The measurement of the particle size distribution is integral to characterization of the sub-micrometer aerosol particle population. The differential mobility analyzer (DMA) has been the primary instrument for such measurements. Aerosol particles are transmitted through the DMA on the condition that their migration time across an electrode separation distance is approximately equal to the advective transport time from the inlet to the outlet; these two travel times are induced by an electric field between the electrodes and an orthogonal particle-free carrier gas flow. However, scientific interest has increasingly shifted toward both the nanometer-scale particle size distribution and the miniaturization of instruments. The classical DMA suffers from severe resolution degradation and diffusional losses of nanometer-scale particles, as well as being ill-suited for lightweight, low-power applications. It is relatively recently that miniaturization of DMAs for portable applications has appeared in the scientific literature. Additionally, an abundance of efforts on DMA design have yielded instruments that can probe the nanometer-scale particle size regime, though their use is restricted to the laboratory as they require powerful pumps and operate at near-turbulent flow conditions.
\r\n\r\nThe opposed migration aerosol classifier (OMAC) is a novel concept for particle electrical mobility classification introduced about a decade ago. In contrast to the DMA, the OMAC transmits particles on the condition that their migration velocity in an electric field is approximately equal to the advective transport velocity by a particle-free flow; the migration velocity is induced by an electric field between two porous electrodes, through which a particle-free cross-flow moves in an anti-parallel direction to the electric field. Because of this flow field arrangement, the length scale over which diffusion must act to affect resolution is the entire electrode separation distance in the OMAC, whereas in the DMA it is smaller by about a factor of the sample-to-carrier gas flow rate ratio. As a result, resolution degradation due to diffusion occurs at a lower operating voltage in the OMAC compared to the DMA. Not only does this suggest a larger dynamic range for the OMAC, but also the capability to classify nanometer-scale particles with greater resolution and lower operating voltages and flow rates.
\r\n\r\nMotivated by the theoretical advantages of an OMAC compared to a DMA, this thesis details the design and characterization of OMAC classifiers to verify the performance of realized OMACs. The capabilities of prototype radial geometry OMACs were first investigated. They demonstrated sub-20 nm particle diameter classification at high resolution using modest flow rates, making them amenable to non-laboratory applications. Additionally, the delayed resolution degradation of OMACs was validated by the maintenance of resolution at operating voltages below those at which a DMA would have experienced severely degraded resolution.
\r\n\r\nVarious applications were then carried out to validate the use of OMACs in both nanometer-scale and sub-micrometer particle size regimes. The first OMAC application was in the field of biomolecule analysis, in which the radial OMAC was operated as an ion mobility spectrometer coupled to a mass spectrometer to resolve conformations of sub-2 nm biomolecules. The resolving power of the radial OMAC was high enough to differentiate peptide stereoisomers and populations of thermally-induced biomolecule conformations.
\r\n\r\nIn the aerosol measurement field, aerosol particle size distributions are typically obtained by passing the sample through an ionization source to impart charges on the sample particles, before mobility separation and detection. The detected signal must be inverted, using detector efficiencies, classifier transfer functions, and charge distributions, to obtain the true particle size distribution. While detector efficiencies and classifier transfer functions are typically well-quantified for the specific instruments used in the measurement, the charge distribution is almost never calculated for the specific measurement conditions. This is due both to the computational expense of, as well as the present impracticability of obtaining all the information needed for carrying out such calculations. Aerosol scientists typically use one parameterization of the charge distribution, regardless of the measurement conditions. Thus, the charge distribution represents the greatest source of bias in particle size distribution measurements. Having demonstrated high resolution of sub-2 nm ions, the radial OMAC was then used to obtain mobility distributions of gas ions formed in a bipolar aerosol charger. These ion mobility distributions were then used to quantify the particle size distribution bias due to the use of the common charge distribution parameterization.
\r\n\r\nIn atmospheric nucleation field, the radial OMAC was deployed as part of an airborne particle detection payload over a large cattle feedlot. Again, the radial OMAC demonstrated the ability to obtain nanometer-scale particle size distributions, that, when paired with a concurrently-deployed DMA, allowed for the measurement of ambient particle size distributions over the entire sub-micrometer size range. A spatially-dense set of such particle size distributions allowed for the calculation of particle growth rates from a clear nucleation event from cattle feedlot emissions.
\r\n\r\nFinally, OMACs were evaluated for their performance at low-flow rate operation to obtain sub-micron particle size distribution for deployment as portable exposure monitors, distributed network area monitors, and unmanned aerial vehicle instrumentation. The radial OMAC showed high fidelity to a reference instrument in reported ambient particle size distributions for nearly 48 hours of unattended operation. A planar geometry OMAC prototype was designed and characterized as well, indicating design and construction issues that caused deviations from ideal behavior. The planer OMAC qualitatively agreed with a reference instrument in reported ambient particle size distributions for about 12 hours of unattended operation. Both radial and planar OMACs were more compact, lower in weight, and less demanding in power consumption than a classical DMA, showing high potential for further miniaturized instrumentation development.
", "doi": "10.7907/Z9T72FF1", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:9725", "collection": "thesis", "collection_id": "9725", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05172016-133615016", "type": "thesis", "title": "Modeling the Effect of Vapor Wall Deposition on the Formation of Secondary Organic Aerosol in Chamber Studies", "author": [ { "family_name": "McVay", "given_name": "Renee Catherine", "orcid": "0000-0001-7766-5009", "clpid": "McVay-Renee-Catherine" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Laboratory chamber experiments are used to investigate formation of secondary organic aerosol (SOA) from biogenic and anthropogenic precursors under a variety of environmental conditions. Simulations of these experiments test our understanding of the prevailing chemistry of SOA formation as well as the dynamic processes occurring in the chamber itself. One dynamic process occurring in the chamber that was only recently recognized is the deposition of vapor species to the Teflon walls of the chamber. Low-volatility products formed from the oxidation of volatile organic compounds (VOCs) deposit on the walls rather than forming SOA, decreasing the amount of SOA formed (quantified as the SOA yield: mass of SOA formed per mass of VOC reacted). In this work, several modeling studies are presented that address the effect of vapor wall deposition on SOA formation in chambers.\r\n\r\nA coupled vapor-particle dynamics model is used to examine the competition among the rates of gas-phase oxidation to low volatility products, wall deposition of these products, and mass transfer to the particle phase. The relative time scales of these rates control the amount of SOA formed by affecting the influence of vapor wall deposition. Simulations show that an effect on SOA yield of changing the vapor-particle mass transfer rate is only observed when SOA formation is kinetically limited. For systems with kinetically limited SOA formation, increasing the rate of vapor-particle mass transfer by increasing the concentration of seed particles is an effective way to minimize the effect of vapor wall deposition.
\r\n\r\nThis coupled vapor-particle dynamics model is then applied to α-pinene ozonolysis SOA experiments. Experiments show that the SOA yield is affected when changing the oxidation rate but not when changing the rate of gas-particle mass transfer by changing the concentration of seed particles. Model simulations show that the absence of an effect of changing the seed particle concentration is consistent with SOA formation being governed by quasi-equilibrium growth, in which gas-particle equilibrium is established much faster than the rate of change of the gas-phase concentration. The observed effect of oxidation rate on SOA yield arises due to the presence of vapor wall deposition: gas-phase oxidation products are produced more quickly and condense preferentially onto seed particles before being lost to the walls. Therefore, for α-pinene ozonolysis, increasing the oxidation rate is the most effective way to mitigate the influence of vapor wall deposition.
\r\n\r\nFinally, the detailed model GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) is used to simulate α-pinene photooxidation SOA experiments. Unexpectedly, α-pinene OH oxidation experiments show no effect when changing either the oxidation rate or the vapor-particle mass transfer rate, whereas GECKO-A predicts that changing the oxidation rate should drastically affect the SOA yield. Sensitivity studies show that the assumed magnitude of the vapor wall deposition rate can greatly affect conclusions drawn from comparisons between simulations and experiments. If vapor wall loss in the Caltech chamber is of order 10-5 s-1, GECKO-A greatly overpredicts SOA during high UV experiments, likely due to an overprediction of second-generation products. However, if instead vapor wall loss in the Caltech chamber is of order 10-3 s-1, GECKO-A greatly underpredicts SOA during low UV experiments, possibly due to missing autoxidation pathways in the α-pinene mechanism.
", "doi": "10.7907/Z9FX77DG", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:9107", "collection": "thesis", "collection_id": "9107", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08192015-043550928", "type": "thesis", "title": "Simulations and Mechanisms of Subtropical Low-cloud Response to Climate Change", "author": [ { "family_name": "Tan", "given_name": "Zhihong", "orcid": "0000-0002-7422-3317", "clpid": "Tan-Zhihong" } ], "thesis_advisor": [ { "family_name": "Schneider", "given_name": "Tapio", "orcid": "0000-0001-5687-2287", "clpid": "Schneider-T" }, { "family_name": "Teixeira", "given_name": "Joao", "clpid": "Teixeira-J" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Schneider", "given_name": "Tapio", "orcid": "0000-0001-5687-2287", "clpid": "Schneider-T" }, { "family_name": "Teixeira", "given_name": "Joao", "clpid": "Teixeira-Joao" }, { "family_name": "Bordoni", "given_name": "Simona", "orcid": "0000-0003-4771-3350", "clpid": "Bordoni-S" }, { "family_name": "Wennberg", "given_name": "Paul O.", "orcid": "0000-0002-6126-3854", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This thesis focuses on improving the simulation skills and the theoretical understanding of the subtropical low cloud response to climate change.
\r\n\r\nFirst, an energetically consistent forcing framework is designed and implemented for the large eddy simulation (LES) of the low-cloud response to climate change. The three representative current-day subtropical low cloud regimes of cumulus (Cu), cumulus-over-stratocumulus, and stratocumulus (Sc) are all well simulated with this framework, and results are comparable to the conventional fixed-SST approach. However, the cumulus response to climate warming subject to energetic constraints differs significantly from the conventional approach with fixed SST. Under the energetic constraint, the subtropics warm less than the tropics, since longwave (LW) cooling is more efficient with the drier subtropical free troposphere. The surface latent heat flux (LHF) also increases only weakly subject to the surface energetic constraint. Both factors contribute to an increased estimated inversion strength (EIS), and decreased inversion height. The decreased Cu-depth contributes to a decrease of liquid water path (LWP) and weak positive cloud feedback. The conventional fixed-SST approach instead simulates a strong increase in LHF and deepening of the Cu layer, leading to a weakly negative cloud feedback. This illustrates the importance of energetic constraints to the simulation and understanding of the sign and magnitude of low-cloud feedback.
\r\n\r\nSecond, an extended eddy-diffusivity mass-flux (EDMF) closure for the unified representation of sub-grid scale (SGS) turbulence and convection processes in general circulation models (GCM) is presented. The inclusion of prognostic terms and the elimination of the infinitesimal updraft fraction assumption makes it more flexible for implementation in models across different scales. This framework can be consistently extended to formulate multiple updrafts and downdrafts, as well as variances and covariances. It has been verified with LES in different boundary layer regimes in the current climate, and further development and implementation of this closure may help to improve our simulation skills and understanding of low-cloud feedback through GCMs.
", "doi": "10.7907/Z9JS9NC9", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:9166", "collection": "thesis", "collection_id": "9166", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09222015-114148959", "primary_object_url": { "basename": "Coggon_Matthew_2015_thesis.pdf", "content": "final", "filesize": 32882973, "license": "other", "mime_type": "application/pdf", "url": "/9166/1/Coggon_Matthew_2015_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Field and Laboratory Studies of Atmospheric Organic Aerosol", "author": [ { "family_name": "Coggon", "given_name": "Matthew Mitchell", "clpid": "Coggon-Matthew-Mitchell" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Sorooshian", "given_name": "Armin", "clpid": "Sorooshian-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis is the culmination of field and laboratory studies aimed at assessing processes that affect the composition and distribution of atmospheric organic aerosol. An emphasis is placed on measurements conducted using compact and high-resolution Aerodyne Aerosol Mass Spectrometers (AMS). The first three chapters summarize results from aircraft campaigns designed to evaluate anthropogenic and biogenic impacts on marine aerosol and clouds off the coast of California. Subsequent chapters describe laboratory studies intended to evaluate gas and particle-phase mechanisms of organic aerosol oxidation.
\r\n\r\nThe 2013 Nucleation in California Experiment (NiCE) was a campaign designed to study environments impacted by nucleated and/or freshly formed aerosol particles. Terrestrial biogenic aerosol with > 85% organic mass was observed to reside in the free troposphere above marine stratocumulus. This biogenic organic aerosol (BOA) originated from the Northwestern United States and was transported to the marine atmosphere during periodic cloud-clearing events. Spectra recorded by a cloud condensation nuclei counter demonstrated that BOA is CCN active. BOA enhancements at latitudes north of San Francisco, CA coincided with enhanced cloud water concentrations of organic species such as acetate and formate.
\r\n\r\nAirborne measurements conducted during the 2011 Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) were aimed at evaluating the contribution of ship emissions to the properties of marine aerosol and clouds off the coast of central California. In one study, analysis of organic aerosol mass spectra during periods of enhanced shipping activity yielded unique tracers indicative of cloud-processed ship emissions (m/z 42 and 99). The variation of their organic fraction (f42 and f99) was found to coincide with periods of heavy (f42 > 0.15; f99 > 0.04), moderate (0.05 < f42 < 0.15; 0.01 < f99 < 0.04), and negligible (f42 < 0.05; f99 < 0.01) ship influence. Application of these conditions to all measurements conducted during E-PEACE demonstrated that a large fraction of cloud droplet (72%) and dry aerosol mass (12%) sampled in the California coastal study region was heavily or moderately influenced by ship emissions. Another study investigated the chemical and physical evolution of a controlled organic plume emitted from the R/V Point Sur. Under sunny conditions, nucleated particles composed of oxidized organic compounds contributed nearly an order of magnitude more cloud condensation nuclei (CCN) than less oxidized particles formed under cloudy conditions. The processing time necessary for particles to become CCN active was short ( < 1 hr) compared to the time needed for particles to become hygroscopic at sub-saturated humidity ( > 4 hr).
\r\n\r\nLaboratory chamber experiments were also conducted to evaluate particle-phase processes influencing aerosol phase and composition. In one study, ammonium sulfate seed was coated with a layer of secondary organic aerosol (SOA) from toluene oxidation followed by a layer of SOA from α-pinene oxidation. The system exhibited different evaporative properties than ammonium sulfate seed initially coated with \u03b1-pinene SOA followed by a layer of toluene SOA. This behavior is consistent with a shell-and-core model and suggests limited mixing among different SOA types. Another study investigated the reactive uptake of isoprene epoxy diols (IEPOX) onto non-acidified aerosol. It was demonstrated that particle acidity has limited influence on organic aerosol formation onto ammonium sulfate seed, and that the chemical system is limited by the availability of nucleophiles such as sulfate.
\r\n\r\n\r\nFlow tube experiments were conducted to examine the role of iron in the reactive uptake and chemical oxidation of glycolaldehyde. Aerosol particles doped with iron and hydrogen peroxide were mixed with gas-phase glycolaldehyde and photochemically aged in a custom-built flow reactor. Compared to particles free of iron, iron-doped aerosols significantly enhanced the oxygen to carbon (O/C) ratio of accumulated organic mass. The primary oxidation mechanism is suggested to be a combination of Fenton and photo-Fenton reactions which enhance particle-phase OH radical concentrations.
", "doi": "10.7907/Z9959FH7", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:8881", "collection": "thesis", "collection_id": "8881", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05222015-145550415", "primary_object_url": { "basename": "SchillingK_thesis.pdf", "content": "final", "filesize": 46529213, "license": "other", "mime_type": "application/pdf", "url": "/8881/1/SchillingK_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Secondary Organic Aerosol Composition Studies Using Mass Spectrometry", "author": [ { "family_name": "Schilling", "given_name": "Katherine Ann", "clpid": "Schilling-Katherine-Ann" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "clpid": "Blake-G-A" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Trace volatile organic compounds emitted by biogenic and anthropogenic sources into the atmosphere can undergo extensive photooxidation to form species with lower volatility. By equilibrium partitioning or reactive uptake, these compounds can nucleate into new aerosol particles or deposit onto already-existing particles to form secondary organic aerosol (SOA). SOA and other atmospheric particulate matter have measurable effects on global climate and public health, making understanding SOA formation a needed field of scientific inquiry. SOA formation can be done in a laboratory setting, using an environmental chamber; under these controlled conditions it is possible to generate SOA from a single parent compound and study the chemical composition of the gas and particle phases. By studying the SOA composition, it is possible to gain understanding of the chemical reactions that occur in the gas phase and particle phase, and identify potential heterogeneous processes that occur at the surface of SOA particles. In this thesis, mass spectrometric methods are used to identify qualitatively and qualitatively the chemical components of SOA derived from the photooxidation of important anthropogenic volatile organic compounds that are associated with gasoline and diesel fuels and industrial activity (C12 alkanes, toluene, and o-, m-, and p-cresols). The conditions under which SOA was generated in each system were varied to explore the effect of NOx and inorganic seed composition on SOA chemical composition. The structure of the parent alkane was varied to investigate the effect on the functionalization and fragmentation of the resulting oxidation products. Relative humidity was varied in the alkane system as well to measure the effect of increased particle-phase water on condensed-phase reactions. In all systems, oligomeric species, resulting potentially from particle-phase and heterogeneous processes, were identified. Imines produced by reactions between (NH4)2SO4 seed and carbonyl compounds were identified in all systems. Multigenerational photochemistry producing low- and extremely low-volatility organic compounds (LVOC and ELVOC) was reflected strongly in the particle-phase composition as well.", "doi": "10.7907/Z93F4MJR", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8911", "collection": "thesis", "collection_id": "8911", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282015-214235298", "primary_object_url": { "basename": "XuanZhang2015thesis.pdf", "content": "final", "filesize": 28424335, "license": "other", "mime_type": "application/pdf", "url": "/8911/1/XuanZhang2015thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Investigation of Fundamental Processes Governing Secondary Organic Aerosol Formation in Laboratory Chambers", "author": [ { "family_name": "Zhang", "given_name": "Xuan", "orcid": "0000-0003-1548-8021", "clpid": "Zhang-Xuan" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Our understanding of the processes and mechanisms by which secondary organic aerosol (SOA) is formed is derived from laboratory chamber studies. In the atmosphere, SOA formation is primarily driven by progressive photooxidation of SOA precursors, coupled with their gas-particle partitioning. In the chamber environment, SOA-forming vapors undergo multiple chemical and physical processes that involve production and removal via gas-phase reactions; partitioning onto suspended particles vs. particles deposited on the chamber wall; and direct deposition on the chamber wall. The main focus of this dissertation is to characterize the interactions of organic vapors with suspended particles and the chamber wall and explore how these intertwined processes in laboratory chambers govern SOA formation and evolution.
\r\n \r\nA Functional Group Oxidation Model (FGOM) that represents SOA formation and evolution in terms of the competition between functionalization and fragmentation, the extent of oxygen atom addition, and the change of volatility, is developed. The FGOM contains a set of parameters that are to be determined by fitting of the model to laboratory chamber data. The sensitivity of the model prediction to variation of the adjustable parameters allows one to assess the relative importance of various pathways involved in SOA formation.
\r\n \r\nA critical aspect of the environmental chamber is the presence of the wall, which can induce deposition of SOA-forming vapors and promote heterogeneous reactions. An experimental protocol and model framework are first developed to constrain the vapor-wall interactions. By optimal fitting the model predictions to the observed wall-induced decay profiles of 25 oxidized organic compounds, the dominant parameter governing the extent of wall deposition of a compound is identified, i.e., wall accommodation coefficient. By correlating this parameter with the molecular properties of a compound via its volatility, the wall-induced deposition rate of an organic compound can be predicted based on its carbon and oxygen numbers in the molecule.
\r\n \r\nHeterogeneous transformation of \u03b4-hydroxycarbonyl, a major first-generation product from long-chain alkane photochemistry, is observed on the surface of particles and walls. The uniqueness of this reaction scheme is the production of substituted dihydrofuran, which is highly reactive towards ozone, OH, and NO3, thereby opening a reaction pathway that is not usually accessible to alkanes. A spectrum of highly-oxygenated products with carboxylic acid, ester, and ether functional groups is produced from the substituted dihydrofuran chemistry, thereby affecting the average oxidation state of the alkane-derived SOA.
\r\n \r\nThe vapor wall loss correction is applied to several chamber-derived SOA systems generated from both anthropogenic and biogenic sources. Experimental and modeling approaches are employed to constrain the partitioning behavior of SOA-forming vapors onto suspended particles vs. chamber walls. It is demonstrated that deposition of SOA-forming vapors to the chamber wall during photooxidation experiments can lead to substantial and systematic underestimation of SOA. Therefore, it is likely that a lack of proper accounting for vapor wall losses that suppress chamber-derived SOA yields contribute substantially to the underprediction of ambient SOA concentrations in atmospheric models.
\r\n", "doi": "10.7907/Z9QZ27WP", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8625", "collection": "thesis", "collection_id": "8625", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07312014-164509193", "primary_object_url": { "basename": "Kangwoo Cho_2015_thesis_entire.pdf", "content": "final", "filesize": 5122341, "license": "other", "mime_type": "application/pdf", "url": "/8625/33/Kangwoo Cho_2015_thesis_entire.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Wastewater Electrolysis Cell for Environmental Pollutants Degradation and Molecular Hydrogen Generation\r ", "author": [ { "family_name": "Cho", "given_name": "Kangwoo", "orcid": "0000-0002-1819-7687", "clpid": "Cho-Kangwoo" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Goddard", "given_name": "William A., III", "clpid": "Goddard-W-A-III" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "This study proposes a wastewater electrolysis cell (WEC) for on-site treatment of human waste coupled with decentralized molecular H2 production. The core of the WEC includes mixed metal oxides anodes functionalized with bismuth doped TiO2 (BiOx/TiO2). The BiOx/TiO2 anode shows reliable electro-catalytic activity to oxidize Cl- to reactive chlorine species (RCS), which degrades environmental pollutants including chemical oxygen demand (COD), protein, NH4+, urea, and total coliforms. The WEC experiments for treatment of various kinds of synthetic and real wastewater demonstrate sufficient water quality of effluent for reuse for toilet flushing and environmental purposes. Cathodic reduction of water and proton on stainless steel cathodes produced molecular H2 with moderate levels of current and energy efficiency. This thesis presents a comprehensive environmental analysis together with kinetic models to provide an in-depth understanding of reaction pathways mediated by the RCS and the effects of key operating parameters. The latter part of this thesis is dedicated to bilayer hetero-junction anodes which show enhanced generation efficiency of RCS and long-term stability.
\r\n\r\nChapter 2 describes the reaction pathway and kinetics of urea degradation mediated by electrochemically generated RCS. The urea oxidation involves chloramines and chlorinated urea as reaction intermediates, for which the mass/charge balance analysis reveals that N2 and CO2 are the primary products. Chapter 3 investigates direct-current and photovoltaic powered WEC for domestic wastewater treatment, while Chapter 4 demonstrates the feasibility of the WEC to treat model septic tank effluents. The results in Chapter 2 and 3 corroborate the active roles of chlorine radicals (Cl\u2022/Cl2-\u2022) based on iR-compensated anodic potential (thermodynamic basis) and enhanced pseudo-first-order rate constants (kinetic basis). The effects of operating parameters (anodic potential and [Cl-] in Chapter 3; influent dilution and anaerobic pretreatment in Chapter 4) on the rate and current/energy efficiency of pollutants degradation and H2 production are thoroughly discussed based on robust kinetic models. Chapter 5 reports the generation of RCS on Ir0.7Ta0.3Oy/BixTi1-xOz hetero-junction anodes with enhanced rate, current efficiency, and long-term stability compared to the Ir0.7Ta0.3Oy anode. The effects of surficial Bi concentration are interrogated, focusing on relative distributions between surface-bound hydroxyl radical and higher oxide.
\r\n", "doi": "10.7907/Z9DZ0676", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8147", "collection": "thesis", "collection_id": "8147", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03192014-130444619", "primary_object_url": { "basename": "thesismain_embed.pdf", "content": "final", "filesize": 45503203, "license": "other", "mime_type": "application/pdf", "url": "/8147/1/thesismain_embed.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Studies of Ambient Organic and Inorganic Aerosol in Southern California", "author": [ { "family_name": "Ensberg", "given_name": "Joseph James", "clpid": "Ensberg-Joseph-James" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Dabdub", "given_name": "Donald", "clpid": "Dabdub-D" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The negative impacts of ambient aerosol particles, or particulate matter (PM), on human health and climate are well recognized. However, owing to the complexity of aerosol particle formation and chemical evolution, emissions control strategies remain difficult to develop in a cost effective manner. In this work, three studies are presented to address several key issues currently stymieing California's efforts to continue improving its air quality.
\r\n\r\nGas-phase organic mass (GPOM) and CO emission factors are used in conjunction with measured enhancements in oxygenated organic aerosol (OOA) relative to CO to quantify the significant lack of closure between expected and observed organic aerosol concentrations attributable to fossil-fuel emissions. Two possible conclusions emerge from the analysis to yield consistency with the ambient organic data: (1) vehicular emissions are not a dominant source of anthropogenic fossil SOA in the Los Angeles Basin, or (2) the ambient SOA mass yields used to determine the SOA formation potential of vehicular emissions are substantially higher than those derived from laboratory chamber studies. Additional laboratory chamber studies confirm that, owing to vapor-phase wall loss, the SOA mass yields currently used in virtually all 3D chemical transport models are biased low by as much as a factor of 4. Furthermore, predictions from the Statistical Oxidation Model suggest that this bias could be as high as a factor of 8 if the influence of the chamber walls could be removed entirely.
\r\n\r\nOnce vapor-phase wall loss has been accounted for in a new suite of laboratory chamber experiments, the SOA parameterizations within atmospheric chemical transport models should also be updated. To address the numerical challenges of implementing the next generation of SOA models in atmospheric chemical transport models, a novel mathematical framework, termed the Moment Method, is designed and presented. Assessment of the Moment Method strengths and weaknesses provide valuable insight that can guide future development of SOA modules for atmospheric CTMs.
\r\n\r\nFinally, regional inorganic aerosol formation and evolution is investigated via detailed comparison of predictions from the Community Multiscale Air Quality (CMAQ version 4.7.1) model against a suite of airborne and ground-based meteorological measurements, gas- and aerosol-phase inorganic measurements, and black carbon (BC) measurements over Southern California during the CalNex field campaign in May/June 2010. Results suggests that continuing to target sulfur emissions with the hopes of reducing ambient PM concentrations may not the most effective strategy for Southern California. Instead, targeting dairy emissions is likely to be an effective strategy for substantially reducing ammonium nitrate concentrations in the eastern part of the Los Angeles Basin.
\r\n", "doi": "10.7907/4J4Q-HP22", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "id": "thesis:7881", "collection": "thesis", "collection_id": "7881", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06102013-101017079", "primary_object_url": { "basename": "Yi-Chun_Chen_2013_Thesis_upload.pdf", "content": "final", "filesize": 6780011, "license": "other", "mime_type": "application/pdf", "url": "/7881/1/Yi-Chun_Chen_2013_Thesis_upload.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Aerosol-Cloud-Precipitation Interactions in Marine Stratocumulus Clouds", "author": [ { "family_name": "Chen", "given_name": "Yi-Chun", "clpid": "Chen-Yi-Chun" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Bordoni", "given_name": "Simona", "clpid": "Bordoni-S" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Stephens", "given_name": "Graeme Leslie", "clpid": "Stephens-G-L" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Marine stratocumulus clouds are generally optically thick and shallow, exerting a net cooling influence on climate. Changes in atmospheric aerosol levels alter cloud microphysics (e.g., droplet size) and cloud macrophysics (e.g., liquid water path, cloud thickness), thereby affecting cloud albedo and Earth\u2019s radiative balance. To understand the aerosol-cloud-precipitation interactions and to explore the dynamical effects, three-dimensional large-eddy simulations (LES) with detailed bin-resolved microphysics are performed to explore the diurnal variation of marine stratocumulus clouds under different aerosol levels and environmental conditions. It is shown that the marine stratocumulus cloud albedo is sensitive to aerosol perturbation under clean background conditions, and to environmental conditions such as large-scale divergence rate and free tropospheric humidity.
\r\n\r\nBased on the in-situ Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) during Jul. and Aug. 2011, and A-Train satellite observation of 589 individual ship tracks during Jun. 2006-Dec. 2009, an analysis of cloud albedo responses in ship tracks is presented. It is found that the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. Under closed cell structure (i.e., cloud cells ringed by a perimeter of clear air), with sufficiently dry air above cloud tops and/or higher cloud top heights, the cloud albedo can become lower in ship tracks. Based on the satellite data, nearly 25% of ship tracks exhibited a decreased albedo. The cloud macrophysical responses are crucial in determining both the strength and the sign of the cloud albedo response to aerosols.
\r\n\r\nTo understand the aerosol indirect effects on global marine warm clouds, multisensory satellite observations, including CloudSat, MODIS, CALIPSO, AMSR-E, ECMWF, CERES, and NCEP, have been applied to study the sensitivity of cloud properties to aerosol levels and to large scale environmental conditions. With an estimate of anthropogenic aerosol fraction, the global aerosol indirect radiative forcing has been assessed.
\r\n\r\nAs the coupling among aerosol, cloud, precipitation, and meteorological conditions in the marine boundary layer is complex, the integration of LES modeling, in-situ aircraft measurements, and global multisensory satellite data analyses improves our understanding of this complex system.
\r\n", "doi": "10.7907/9SGJ-TT23", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7612", "collection": "thesis", "collection_id": "7612", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04112013-190107672", "primary_object_url": { "basename": "CravenJill2013.pdf", "content": "final", "filesize": 63955245, "license": "other", "mime_type": "application/pdf", "url": "/7612/1/CravenJill2013.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Studies of Ambient and Chamber Aerosol Composition Using the Aerosol Mass Spectrometer", "author": [ { "family_name": "Craven", "given_name": "Jill Suzanne", "clpid": "Craven-Jill-Suzanne" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis presents composition measurements for atmospherically relevant inorganic and organic aerosol from laboratory and ambient measurements using the Aerodyne aerosol mass spectrometer. Studies include the oxidation of dodecane in the Caltech environmental chambers, and several aircraft- and ground-based field studies, which include the quantification of wildfire emissions off the coast of California, and Los Angeles urban emissions.
\r\n\r\nThe oxidation of dodecane by OH under low NO conditions and the formation of secondary organic aerosol (SOA) was explored using a gas-phase chemical model, gas-phase CIMS measurements, and high molecular weight ion traces from particle- phase HR-TOF-AMS mass spectra. The combination of these measurements support the hypothesis that particle-phase chemistry leading to peroxyhemiacetal formation is important. Positive matrix factorization (PMF) was applied to the AMS mass spectra which revealed three factors representing a combination of gas-particle partitioning, chemical conversion in the aerosol, and wall deposition.
\r\n\r\nAirborne measurements of biomass burning emissions from a chaparral fire on the central Californian coast were carried out in November 2009. Physical and chemical changes were reported for smoke ages 0 \u2013 4 h old. CO2 normalized ammonium, nitrate, and sulfate increased, whereas the normalized OA decreased sharply in the first 1.5 - 2 h, and then slowly increased for the remaining 2 h (net decrease in normalized OA). Comparison to wildfire samples from the Yucatan revealed that factors such as relative humidity, incident UV radiation, age of smoke, and concentration of emissions are important for wildfire evolution.
\r\n\r\nGround-based aerosol composition is reported for Pasadena, CA during the summer of 2009. The OA component, which dominated the submicron aerosol mass, was deconvolved into hydrocarbon-like organic aerosol (HOA), semi-volatile oxidized organic aerosol (SVOOA), and low-volatility oxidized organic aerosol (LVOOA). The HOA/OA was only 0.08\u20130.23, indicating that most of Pasadena OA in the summer months is dominated by oxidized OA resulting from transported emissions that have undergone photochemistry and/or moisture-influenced processing, as apposed to only primary organic aerosol emissions. Airborne measurements and model predictions of aerosol composition are reported for the 2010 CalNex field campaign.
", "doi": "10.7907/J69H-EK18", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7790", "collection": "thesis", "collection_id": "7790", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312013-115629933", "primary_object_url": { "basename": "CLL_PhD_thesis.pdf", "content": "final", "filesize": 21097660, "license": "other", "mime_type": "application/pdf", "url": "/7790/14/CLL_PhD_thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Investigations of Secondary Organic Aerosol Formation in Laboratory Chambers", "author": [ { "family_name": "Loza", "given_name": "Christine Lauren", "clpid": "Loza-Christine-Lauren" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Sander", "given_name": "Stanley P.", "clpid": "Sander-S-P" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Secondary organic aerosol (SOA) is produced in the atmosphere by oxidation of volatile organic compounds. Laboratory chambers are used understand the formation mechanisms and evolution of SOA formed under controlled conditions. This thesis presents studies of SOA formed from anthropogenic and biogenic precursors and discusses the effects of chamber walls on suspended vapors and particles.
\r\n\r\nDuring a chamber experiment, suspended vapors and particles can interact with the chamber walls. Particle wall loss is relatively well-understood, but vapor wall losses have received little study. Vapor wall loss of 2,3-epoxy-1,4-butanediol (BEPOX) and glyoxal was identified, quantified, and found to depend on chamber age and relative humidity.
\r\n\r\nParticles reside in the atmosphere for a week or more and can evolve chemically during that time period, a process termed aging. Simulating aging in laboratory chambers has proven to be challenging. A protocol was developed to extend the duration of a chamber experiment to 36 h of oxidation and was used to evaluate aging of SOA produced from m-xylene. Total SOA mass concentration increased and then decreased with increasing photooxidation suggesting a transition from functionalization to fragmentation chemistry driven by photochemical processes. SOA oxidation, measured as the bulk particle elemental oxygen-to-carbon ratio and fraction of organic mass at m/z 44, increased continuously starting after 5 h of photooxidation.
\r\n\r\nThe physical state and chemical composition of an organic aerosol affect the mixing of aerosol components and its interactions with condensing species. A laboratory chamber protocol was developed to evaluate the mixing of SOA produced sequentially from two different sources by heating the chamber to induce particle evaporation. Using this protocol, SOA produced from toluene was found to be less volatile than that produced from a-pinene. When the two types of SOA were formed sequentially, the evaporation behavior most closely represented that of SOA from the second parent hydrocarbon, suggesting that the structure of the mixed SOA particles resembles a core of SOA from the first precursor coated by a layer of SOA from the second precursor, indicative of limiting mixing.
", "doi": "10.7907/WZXD-KX70", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7521", "collection": "thesis", "collection_id": "7521", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03162013-090820386", "type": "thesis", "title": "Chemistry of Secondary Organic Aerosol Formation", "author": [ { "family_name": "Yee", "given_name": "Lindsay Diana", "clpid": "Yee-Lindsay-Diana" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The photooxidation of volatile organic compounds (VOCs) in the atmosphere can lead to the formation of secondary organic aerosol (SOA), a major component of fine particulate matter. Improvements to air quality require insight into the many reactive intermediates that lead to SOA formation, of which only a small fraction have been measured at the molecular level. This thesis describes the chemistry of secondary organic aerosol (SOA) formation from several atmospherically relevant hydrocarbon precursors. Photooxidation experiments of methoxyphenol and phenolic compounds and C12 alkanes were conducted in the Caltech Environmental Chamber. These experiments include the first photooxidation studies of these precursors run under sufficiently low NOx levels, such that RO2 + HO2 chemistry dominates, an important chemical regime in the atmosphere. Using online Chemical Ionization Mass Spectrometery (CIMS), key gas-phase intermediates that lead to SOA formation in these systems were identified. With complementary particle-phase analyses, chemical mechanisms elucidating the SOA formation from these compounds are proposed.
\r\n\r\nThree methoxyphenol species (phenol, guaiacol, and syringol) were studied to model potential photooxidation schemes of biomass burning intermediates. SOA yields (ratio of mass of SOA formed to mass of primary organic reacted) exceeding 25% are observed. Aerosol growth is rapid and linear with the organic conversion, consistent with the formation of essentially non-volatile products. Gas and aerosol-phase oxidation products from the guaiacol system show that the chemical mechanism consists of highly oxidized aromatic species in the particle phase. Syringol SOA yields are lower than that of phenol and guaiacol, likely due to unique chemistry dependent on methoxy group position.
\r\n\r\nThe photooxidation of several C12 alkanes of varying structure n-dodecane, 2-methylundecane, cyclododecane, and hexylcyclohexane) were run under extended OH exposure to investigate the effect of molecular structure on SOA yields and photochemical aging. Peroxyhemiacetal formation from the reactions of several multifunctional hydroperoxides and aldehyde intermediates was found to be central to organic growth in all systems, and SOA yields increased with cyclic character of the starting hydrocarbon. All of these studies provide direction for future experiments and modeling in order to lessen outstanding discrepancies between predicted and measured SOA.
", "doi": "10.7907/BPKE-M777", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7699", "collection": "thesis", "collection_id": "7699", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05122013-183426374", "type": "thesis", "title": "Physical Investigations of Small Particles: (I) Aerosol Particle Charging and Flux Enhancement and (II) Whispering Gallery Mode Sensing", "author": [ { "family_name": "L\u00f3pez-Yglesias", "given_name": "Xerxes F.", "clpid": "L\u00f3pez-Yglesias-Xerxes-F" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Beauchamp", "given_name": "Jack L.", "clpid": "Beauchamp-J-L" }, { "family_name": "Porter", "given_name": "Frank C.", "clpid": "Porter-F-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Part I
\r\n\r\nParticles are a key feature of planetary atmospheres. On Earth they represent the greatest source of uncertainty in the global energy budget. This uncertainty can be addressed by making more measurement, by improving the theoretical analysis of measurements, and by better modeling basic particle nucleation and initial particle growth within an atmosphere. This work will focus on the latter two methods of improvement.
\r\n\r\nUncertainty in measurements is largely due to particle charging. Accurate descriptions of particle charging are challenging because one deals with particles in a gas as opposed to a vacuum, so different length scales come into play. Previous studies have considered the effects of transition between the continuum and kinetic regime and the effects of two and three body interactions within the kinetic regime. These studies, however, use questionable assumptions about the charging process which resulted in skewed observations, and bias in the proposed dynamics of aerosol particles. These assumptions affect both the ions and particles in the system. Ions are assumed to be point monopoles that have a single characteristic speed rather than follow a distribution. Particles are assumed to be perfect conductors that have up to five elementary charges on them. The effects of three body interaction, ion-molecule-particle, are also overestimated. By revising this theory so that the basic physical attributes of both ions and particles and their interactions are better represented, we are able to make more accurate predictions of particle charging in both the kinetic and continuum regimes.
\r\n\r\nThe same revised theory that was used above to model ion charging can also be applied to the flux of neutral vapor phase molecules to a particle or initial cluster. Using these results we can model the vapor flux to a neutral or charged particle due to diffusion and electromagnetic interactions. In many classical theories currently applied to these models, the finite size of the molecule and the electromagnetic interaction between the molecule and particle, especially for the neutral particle case, are completely ignored, or, as is often the case for a permanent dipole vapor species, strongly underestimated. Comparing our model to these classical models we determine an \u201cenhancement factor\u201d to characterize how important the addition of these physical parameters and processes is to the understanding of particle nucleation and growth.
\r\n\r\nPart II
\r\n\r\nWhispering gallery mode (WGM) optical biosensors are capable of extraordinarily sensitive specific and non-specific detection of species suspended in a gas or fluid. Recent experimental results suggest that these devices may attain single-molecule sensitivity to protein solutions in the form of stepwise shifts in their resonance wavelength, \\lambda_{R}, but present sensor models predict much smaller steps than were reported. This study examines the physical interaction between a WGM sensor and a molecule adsorbed to its surface, exploring assumptions made in previous efforts to model WGM sensor behavior, and describing computational schemes that model the experiments for which single protein sensitivity was reported. The resulting model is used to simulate sensor performance, within constraints imposed by the limited material property data. On this basis, we conclude that nonlinear optical effects would be needed to attain the reported sensitivity, and that, in the experiments for which extreme sensitivity was reported, a bound protein experiences optical energy fluxes too high for such effects to be ignored.
", "doi": "10.7907/DP06-K961", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:6880", "collection": "thesis", "collection_id": "6880", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03292012-204204319", "primary_object_url": { "basename": "thesismain.pdf", "content": "final", "filesize": 12051492, "license": "other", "mime_type": "application/pdf", "url": "/6880/1/thesismain.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Computational Modeling Studies of Fundamental Aerosol-Cloud Interactions", "author": [ { "family_name": "Lebo", "given_name": "Zachary John", "clpid": "Lebo-Zachary-John" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Schneider", "given_name": "Tapio", "clpid": "Schneider-T" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Li", "given_name": "Juilin F.", "clpid": "Li-J-F" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Basic questions regarding the interaction between changes in human activity and the atmosphere remain unanswered. Among these, the link between aerosol particles and cloud formation and development, especially in an altered climate, is a large point of uncertainty in recent climate projections. This should come as no surprise given the uncertainty in model parameters required to predict droplet activation, even in the most detailed models used for climate predictions. Here, a detailed spectral mixed-phase microphysics scheme and a state-of-the-art continuous two-dimensional (2-D) aerosol-droplet microphysics scheme have been developed and coupled to the Weather Research and Forecasting (WRF) model to more closely analyze the effects of aerosol perturbations on single clouds or cloud systems with the hope of ultimately improving numerical parameterizations used by microphysics schemes in general circulation models (GCMs).
\r\n\r\nThe continuous 2-D aerosol-droplet model is developed to explicitly treat the entire spectrum of aerosol, haze droplets, cloud droplets, and drizzle drops while allowing the solute mass spectrum to evolve within the droplets. In other words, the aerosol mass is conserved and regeneration of aerosol particles upon droplet evaporation is physically accurate without any a priori assumptions. The model is tested by performing simulations of marine stratocumulus and the results are compared with those from the aforementioned bin and bulk models. It is shown that microphysical processing of aerosols alone results in a large shift in the aerosol spectrum toward larger particles (via collision-coalescence of droplets). This could have potentially large effects on the activation of regenerated particles. Future studies with the model will address the need for better parameterizations of the aerosol regeneration process.
\r\n\r\nThe spectral mixed-phase microphysics scheme is used in conjunction with a two-moment bulk microphysics model to study the effect of aerosol perturbations on deep convective clouds. The bin model shows that with an increase in aerosol number concentration comes an invigoration and a decrease in precipitation. On the other hand, the bulk model suggests that the storm ought to weaken and precipitation will increase in a more polluted environment. The invigoration predicted by the bin model is a result of the suppression of the collision-coalescence process that permits more droplets to be lofted above the freezing level, hence increasing the bulk freezing rate aloft. The additional freezing and subsequent deposition acts to increase the latent heating and thus increase buoyancy. However, the cloud particles in the polluted cases are now smaller and more numerous and consequently have a shorter evaporation/sublimation timescale and a longer sedimentation time-scale. The ultimate result is for precipitation to decrease in conjunction with a moistening of the mid- to upper-troposphere. The difference in the sign of the aerosol effect between the two models is thought to be related to the saturation adjustment scheme used in the bulk model and is addressed by including an explicit treatment of condensation and activation within the bulk model, similar to the algorithm utilized in the bin model. The results of the inter-model comparison demonstrate the significance of the saturation adjustment assumption on the sign and magnitude of the aerosol effect on deep convective clouds.
", "doi": "10.7907/HH11-8N22", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:7073", "collection": "thesis", "collection_id": "7073", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05242012-112013951", "primary_object_url": { "basename": "Metcalf2012_thesis-final.pdf", "content": "final", "filesize": 61773691, "license": "other", "mime_type": "application/pdf", "url": "/7073/1/Metcalf2012_thesis-final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Atmospheric Black Carbon: Measurements in the Los Angeles Atmosphere and Aging by Condensation of Organic Aerosol", "author": [ { "family_name": "Metcalf", "given_name": "Andrew Richard", "orcid": "0000-0003-0385-1356", "clpid": "Metcalf-Andrew-Richard" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Jonsson", "given_name": "Haflidi H.", "clpid": "Jonsson-H-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Aerosol particles in the atmosphere scatter and absorb solar radiation; an interaction that yields the largest uncertainty in models of future climate change. While most aerosols scatter light and, therefore, cool the environment, absorbing aerosol warms the environment. In particular, black carbon (BC) aerosol, the largest component of absorbing aerosol, may exhibit the second-largest forcing on climate behind greenhouse gases. In addition, the mixing state of BC aerosol, or the degree to which a BC core is coated with a scattering substance, may significantly increase the absorbing potential of BC. This thesis presents results from field and laboratory studies of BC aerosol, its mixing state in the atmosphere, and how it ages in the presence of condensing secondary organic aerosol.
\r\n\r\nA major field study, CalNex 2010, was conducted in Southern California to study air quality and climate change issues. Measurements of BC aerosol in and around the Los Angeles (LA) Basin reveal the evolution of BC aerosol from a thinly coated state near sources in the eastern LA Basin to a more thickly coated state in the outflow regions of the Basin. While the majority of BC aerosol emitted in the LA Basin remains near the surface, some BC aerosol is transported to the free troposphere through sea-breeze and mountain-flow coupling. BC aerosol above the inversion layer tends to be thickly coated, indicating that it is more aged than the BC measured near the surface.
\r\n\r\nTo understand how the mixing state of BC evolves with secondary formation of species in the atmosphere, carefully controlled environmental chamber experiments were conducted. Two types of secondary organic aerosol (SOA) precursors, alpha-pinene and naphthalene, were reacted in the chamber to condense secondary products onto BC seed aerosol. The rate of growth and magnitude of absorption enhancement due to the secondary coating on BC was measured, revealing that growth of coatings is diffusion-limited. Particle composition measurements reveal that condensed SOA onto BC seed particles is nearly identical to nucleated SOA from the same parent hydrocarbon. Measurements of coating thickness and optical properties provide insight to single-particle SOA growth and volatility.
", "doi": "10.7907/YZY9-EW06", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6754", "collection": "thesis", "collection_id": "6754", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12152011-220323752", "type": "thesis", "title": "Mass Spectrometric Analysis of Organic Aerosol Composition: Laboratory and Ambient", "author": [ { "family_name": "Chan", "given_name": "Man Nin", "orcid": "0000-0002-2384-2695", "clpid": "Chan-Man-Nin" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Organic compounds contribute a significant mass fraction of ambient aerosol and play a role in determining the physiochemical properties of ambient aerosol. A significant fraction of organic aerosol is secondary organic aerosol (SOA), which is produced when the volatile organic compounds (VOCs) originated from various anthropogenic and biogenic sources react with atmospheric oxidants such as ozone, hydroxyl radicals, and nitrate radicals to form lower volatility organic compounds, which subsequently partition into the particle phase. Understanding the composition of ambient aerosol is crucial for identifying their sources and formation mechanisms and predicting their properties and effects on various ambient processes. This thesis focuses on investigating the composition of laboratory\u2013generated SOA formed from the oxidation of biogenic VOCs of atmospheric importance (isoprene and \u03b2\u2013caryophyllene) and ambient aerosol collected in the field campaigns using advanced mass spectrometric techniques. By comparing the mass spectrometric data collected for the both laboratory\u2013generated SOA and ambient aerosol, we propose reaction pathways and new chemical tracers for these biogenic VOCs, which enhance our knowledge of the composition, sources, and formation pathways of SOA in the atmosphere. With a better knowledge of the SOA composition, a product\u2013specific model is proposed to predict the composition and aerosol mass yields (mass of SOA formed per mass of hydrocarbon reacted) of laboratory\u2013generated \u03b1\u2013pinene SOA. ", "doi": "10.7907/CGKH-EW24", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:7101", "collection": "thesis", "collection_id": "7101", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302012-163207555", "primary_object_url": { "basename": "downard_thesis.pdf", "content": "final", "filesize": 4301489, "license": "other", "mime_type": "application/pdf", "url": "/7101/5/downard_thesis.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Classification of Sub-10 nm Aerosol: Theory, Instrument Development, and Experiment", "author": [ { "family_name": "Downard", "given_name": "Andrew Joseph", "clpid": "Downard-Andrew-Joseph" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The large diffusion coefficients of sub-10 nm aerosol have posed a long-standing challenge to the aerosol community; to understand nucleation and early growth, there is a need for methods such as those presented here that transmit a strong, high resolution signal of classified charged aerosol to the detector. I introduce a framework for comparison of the Flagan Laboratory classifiers to other instruments, and I show why our instruments perform favorably relative to these alternatives. Reducing the size of the classification region reduces the effect of diffusion on performance and will ultimately enable the development of personal health monitors. The deployment of our instruments to the Cosmics Leaving OUtdoor Droplets experiment at CERN motivated a deeper look into detector performance and design for extreme operating conditions. I caution about the possible interference of ion nucleation with measurements and introduce a process for optimizing detector performance at arbitrary temperature. My experience with aerosol classifications has inspired the invention of separation methods for related fields; I conclude by describing methods for the high resolution separation of gas ions and of aqueous particles such as proteins and antibodies.", "doi": "10.7907/KP0F-8T32", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6405", "collection": "thesis", "collection_id": "6405", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05182011-094338191", "primary_object_url": { "basename": "thesismain.pdf", "content": "final", "filesize": 4695173, "license": "other", "mime_type": "application/pdf", "url": "/6405/1/thesismain.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Studies of Chamber Organic Aerosol using an Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer", "author": [ { "family_name": "Chhabra", "given_name": "Puneet Singh", "clpid": "Chhabra-Puneet-Singh" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Secondary organic aerosol (SOA) contributes a substantial fraction to total ambient particulate mass. SOA is a complex mixture of different organic species formed via many gas- and particle-phase reaction pathways. The Aerodyne aerosol mass spectrometer (AMS) has become a standard tool in measuring the bulk chemical composition of SOA in realtime. In addition to acquiring mass spectra of SOA, the high-resolution time-of-flight AMS, or HR-ToF-AMS, can distinguish and quantify ions with the same nominal mass but different elemental compositions. This thesis presents results from several studies in which the HR-ToF-AMS is used to chemically characterize SOA generated in chamber experiments.
\r\n\r\nGlyoxal is a common oxidation product of both biogenic and anthropogenic volatile organic compounds (VOCs) and is known to partition into wet inorganic aerosol. Chamber studies of glyoxal uptake onto ammonium sulfate aerosol are conducted to better understand the mechanisms controlling glyoxal uptake onto ambient aerosol. Organic growth due to glyoxal uptake was found to be reversible under dark conditions. HR-ToF-AMS spectra provide evidence for glyoxal dimers and trimers existing in the particle phase. HR-ToF-AMS spectra indicate the irreversible formation of carbon-nitrogen compounds in the aerosol. Organosulfates are not detected under dark conditions; however, active photochemistry was found to occur within aerosol during irradiated experiments. Carboxylic acids and organic esters are identified within the aerosol. An organosulfate, which had been previously assigned as glyoxal sulfate in ambient samples and chamber studies of isoprene oxidation, is observed only in the irradiated experiments. Comparison with a laboratory-synthesized standard and chemical considerations strongly suggest that this organosulfate is glycolic acid sulfate, an isomer of the previously proposed glyoxal sulfate.
\r\n\r\nDevelopments in HR-ToF-AMS data analysis have allowed for the measurement of the elemental composition of SOA. Additional graphical representations of AMS spectra and elemental composition have been developed to explain the oxidative and aging processes of SOA. It has been shown previously that oxygenated organic aerosol (OOA) components from ambient and laboratory data fall within a triangular region in the f44 vs. f43 space, where f44 and f43 are the ratios of the organic signal at m/z 44 and 43 to the total organic signal, respectively; we refer to this model as the \"triangle plot.\" Alternatively, the Van Krevelen diagram has been used to plot the elemental composition of SOA and describe the evolution of functional groups in SOA. The variability of SOA formed in chamber experiments from twelve different precursors in both \"triangle plot\" and Van Krevelen domains are investigated. Spectral and elemental data from the high-resolution Aerodyne aerosol mass spectrometer are compared to offline species identification analysis and FTIR filter analysis to better understand the changes in functional and elemental composition inherent in SOA formation and aging. SOA formed under high- and low-NOx conditions occupy similar areas in the \"triangle plot\" and Van Krevelen diagram, and SOA generated from already-oxidized precursors starts higher on the \"triangle plot.\" The most oxidized SOA come from the photooxidation of methoxyphenol precursors which yielded SOA O/C ratios near unity. \u221d-pinene ozonolysis and naphthalene photooxidation SOA systems have had the highest degree of mass closure in previous chemical characterization studies and also show the best agreement between AMS elemental composition measurements and elemental composition of identified species. In general the elemental composition of chamber SOA follows a slope shallower than -1 on the Van Krevelen diagram. From the spectra of SOA studied, the triangular region originally constructed with ambient OOA components with chamber aerosol can be reproduced. Ambient data in the middle of the triangle represent the ensemble average of many different SOA precursors, ages, and oxidative processes.
", "doi": "10.7907/2FKC-Y116", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:5993", "collection": "thesis", "collection_id": "5993", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08172010-150049831", "type": "thesis", "title": "Investigations of Global Chemistry-Climate Interactions and Organic Aerosol Using Atmospheric Modeling", "author": [ { "family_name": "Pye", "given_name": "Havala Olson Taylor", "clpid": "Pye-Havala-Olson-Taylor" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Aerosol, or particulate matter (PM), is an important component of the atmosphere responsible for negative health impacts, environmental degradation, reductions in visibility, and climate change. In this work, the global chemical transport model, GEOS-Chem, is used as a tool to examine chemistry-climate interactions and organic aerosols.
\r\n\r\nGEOS-Chem is used to simulate present-day (year 2000) and future (year 2050) sulfate, nitrate, and ammonium aerosols and investigate the potential effects of changes in climate and emissions on global budgets and U.S. air quality. Changes in a number of meteorological parameters, such as temperature and precipitation, are potentially important for aerosols and could lead to increases or decreases in PM concentrations. Although projected changes in sulfate and nitrate precursor emissions favor lower PM concentrations over the U.S., projected increases in ammonia emissions could result in higher nitrate concentrations.
\r\n\r\nThe organic aerosol simulation in GEOS-Chem is updated to include aerosol from primary semivolatile organic compounds (SVOCS), intermediate volatility compounds (IVOCs), NOx dependent terpene aerosol, and aerosol from isoprene + NO3 reaction. SVOCs are identified as the largest global source of organic aerosol even though their atmospheric transformation is highly uncertain and emissions are probably underestimated. As a result of significant nighttime terpene emissions, fast reaction of monoterpenes with the nitrate radical, and high aerosol yields from NO3 oxidation, biogenic hydrocarbons reacting with the nitrate radical are expected to be a major contributor to surface level aerosol concentrations in anthropogenically influenced areas such as the United States. Globally, 69 to 88 Tg/yr of aerosol is predicted to be produced annually, approximately 22 to 24 Tg/yr of which is from biogenic hydrocarbons.
", "doi": "10.7907/WCT5-RM26", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:11762", "collection": "thesis", "collection_id": "11762", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05172011-160342650", "primary_object_url": { "basename": "crounse_thesis_final.pdf", "content": "final", "filesize": 27067752, "license": "other", "mime_type": "application/pdf", "url": "/11762/1/crounse_thesis_final.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Atmospheric Reactive Trace Gas Observations in Field and Chamber Studies Using CF\u2083O\u207b Chemical Ionization Mass Spectrometry", "author": [ { "family_name": "Crounse", "given_name": "John D.", "orcid": "0000-0001-5443-729X", "clpid": "Crounse-John-D" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "clpid": "Blake-G-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This dissertation describes the development of chemical ionization mass spectrometry (CIMS) instrumentation and methods utilizing the CF3O- reagent ion for the sensitive, specific, and direct detection of many oxygenated volatile organic compounds (OVOC) and inorganic reactive trace gases in the atmosphere. These species include HNO3, HONO, HO2NO2, SO2, HCN, H2O2, CH3OOH, CH3(O)OOH, HC(O)OH, CH3C(O)OH, HC(O)CH2OH, CH3C(O)CH2OH, organic hydroperoxides (ROOH), and many additional multifunctional species (e.g., hydroxynitrates, hydroxycarbonyls, hydroxyhydroperoxides, carbonylnitrates, carbonylhydroperoxides, etc.).
\r\n\r\nCF3O--tandem mass spectrometry (MSMS) is demonstrated to be useful for distinguishing and individual quantification of certain isobaric compounds, as well as solving instrumental background problems for certain species. This technology is applied in field studies conducted from aircraft and ground-based platforms and to chamber studies investigating VOC oxidation and organic aerosol formation mechanisms. Comparisons with simultaneous observations from other instrumentation for several species show good agreement with CIMS observations. CF3O--CIMS observations of HCN (a biomass burning tracer) from aircraft are used to quantify the impact of biomass burning emissions to the Mexico City region in March 2006. Biomass burning emissions are shown to contribute significantly to a number of gas and aerosol phase pollutants even in the midst of the large anthropogenic pollution emissions from Mexico City. The analysis of the photochemical aging of a fire plume over the Yucatan Peninsula (March 2006) is also reported. Observations indicate intense chemistry occurring within the fire plume evidenced by high OH levels, fast production of H2O2 and conversion of NO and NO2 (NOx) into peroxyacetylnitrate (PAN) and aerosol nitrate. This rapid chemistry is likely driven by photolysis of HONO, which is observed to be emitted in high amounts from these fires.
\r\n\r\nThe CIMS methods are applied to studies of VOC oxidation and organic aerosol formation conducted in chamber experiments. Specifically, new insights gained from the study of isoprene oxidation under high and low NOx conditions are reported. We quantify the formation of small carboxylic acids as well as C5-hydroxynitrates from the oxidation of isoprene under high NOx conditions. Under low NOx conditions, we show that C5-hydroxyhydroperoxides are formed in high yield. Subsequent oxidation of these hydroxyhydroperoxides is shown to occur through a unique HOx neutral mechanism that generates C5-epoxydiols, a likely precursor to organic aerosol.
\r\n\r\nWe utilize the high sensitivity and specificity of CF3O- -CIMS to study novel intermolecular hydrogen-shift isomerization processes in peroxy radicals formed during isoprene oxidation. We find these rates to be substantially slower than recent theoretical predictions; however, we find these isomerization rates to be fast enough that they are important in atmospheric isoprene oxidation in regions where lifetimes become long. Globally, we estimate 8-11% of isoprene peroxy radicals react through 1,6-H-shift isomerization reactions.
", "doi": "10.7907/JMSN-NF98", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:6363", "collection": "thesis", "collection_id": "6363", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04292011-155605494", "primary_object_url": { "basename": "Thesis_final.pdf", "content": "final", "filesize": 11780488, "license": "other", "mime_type": "application/pdf", "url": "/6363/1/Thesis_final.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Insights into the Isoprene Photochemical Cascade", "author": [ { "family_name": "Paulot", "given_name": "Fabien Georges Andr\u00e9", "clpid": "Paulot-Fabien-Georges-Andr\u00e9" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Sander", "given_name": "Stanley P.", "clpid": "Sander-S-P" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Isoprene emissions are the single largest source of non-methane reduced carbon to the atmosphere. Proper simulation of the effect of its photooxidation on regional air quality and secondary organic aerosol formation requires detailed multi-generation and multi-phase photochemical mechanisms. In this work, I first demonstrate that CF3O- chemical ionization mass spectrometry (CIMS) is a powerful method to probe isoprene photochemical oxidation. Under high NOx, isoprene nitrates and their photochemical products are directly observed and quantified. As isoprene nitrates are critical to the impact of isoprene photochemistry on ozone, these observations provide an important constraint on the effect of isoprene emissions on air quality in polluted and biogenic rich regions (e.g., Southeastern United States). The use of tandem CIMS in association with isotopically labelled hydroxy radicals is used to identify dihydroxyepoxides as major products of isoprene photooxidation in low NOx conditions. This class of compounds may provide an important precursor for secondary organic aerosols under acidic conditions. The chemical mechanism derived from these laboratory observations is then incorporated in a chemical transport model to assess the impact of isoprene photooxidation on atmospheric chemistry. I examine how the photooxidation of isoprene impacts the budget of formic and acetic acids, two ubiquitous trace gases whose sources are poorly constrained. Comparison with observations from satellite, ground and aircraft platforms, reveal a major missing source that may originate from the aging of secondary organic aerosols. Finally, the consequences of the multi-scale interplay between NOx and isoprene photochemistry on the tropical budget of ozone are examined using forward and adjoint sensitivity simulations.", "doi": "10.7907/C11Q-E180", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:6452", "collection": "thesis", "collection_id": "6452", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05262011-132849976", "primary_object_url": { "basename": "KMSpencer_thesisfinal.pdf", "content": "final", "filesize": 1070495, "license": "other", "mime_type": "application/pdf", "url": "/6452/1/KMSpencer_thesisfinal.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Constraining Anthropogenic and Biogenic Emissions using Chemical Ionization Mass Spectrometry", "author": [ { "family_name": "Spencer", "given_name": "Kathleen Marie", "clpid": "Spencer-Kathleen-Marie" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" } ], "thesis_committee": [ { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "clpid": "Blake-G-A" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Numerous gas-phase anthropogenic and biogenic compounds are emitted into the atmosphere. These gases undergo oxidation to form other gas-phase species and particulate matter. Whether directly or indirectly, primary pollutants, secondary gas-phase products, and particulate matter all pose health and environmental risks. In this work, ambient measurements conducted using chemical ionization mass spectrometry are used as a tool for investigating regional air quality.
\r\n\r\nAmbient measurements of peroxynitric acid (HO\u2082NO\u2082) were conducted in Mexico City. A method of inferring the rate of ozone production, PO3, is developed based on observations of HO\u2082NO\u2082, NO, and NO\u2082. Comparison of this observationally based PO3 to a highly constrained photochemical box model indicates that regulations aimed at reducing ozone levels in Mexico City by reducing NOx concentrations may be effective at higher NOx levels than predicted using accepted photochemistry.
\r\n\r\nMeasurements of SO\u2082 and particulate sulfate were conducted over the Los Angeles basin in 2008 and are compared to measurements made in 2002. A large decrease in SO\u2082 concentration and a change in spatial distribution are observed. Nevertheless, only a modest reduction in sulfate concentration is observed at ground sites within the basin. Possible explanations for these trends are investigated.
\r\n\r\nTwo techniques, single and triple quadrupole chemical ionization mass spectrometry, were used to quantify ambient concentrations of biogenic oxidation products, hydroxyacetone and glycolaldehyde. The use of these techniques demonstrates the advantage of triple quadrupole mass spectrometry for separation of mass analogues, provided the collision-induced daughter ions are sufficiently distinct. Enhancement ratios of hydroxyacetone and glycolaldehyde in Californian biomass burning plumes are presented as are concentrations of these compounds at a rural ground site downwind of Sacramento.
", "doi": "10.7907/XRFJ-2Q92", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:5955", "collection": "thesis", "collection_id": "5955", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06222010-150731880", "primary_object_url": { "basename": "Thesis.pdf", "content": "final", "filesize": 2618850, "license": "other", "mime_type": "application/pdf", "url": "/5955/1/Thesis.pdf", "version": "v10.0.0" }, "type": "thesis", "title": "Investigating Sources and Sinks of Organic Aerosols: NO\u2083-initiated Oxidation of Isoprene and Heterogeneous Oxidation of Organic Aerosol\r ", "author": [ { "family_name": "Kwan", "given_name": "Alan Jake-Man", "clpid": "Kwan-Alan-Jake-Man" } ], "thesis_advisor": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "thesis_committee": [ { "family_name": "Sessions", "given_name": "Alex L.", "clpid": "Sessions-A-L" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Secondary organic aerosol (SOA) are important components in atmospheric processes and significantly impact human health. The complexity of SOA composition and formation processes has hampered efforts to fully characterize their impacts, and to predict how those impacts will be affected by changes in climate and human activity. Here, we explore SOA formation in the laboratory by coupling an environmental chamber with a suite of analytical tools, including a gas-phase mass spectrometry technique that is well suited for tracking the hydrocarbon oxidation processes that drive SOA formation. Focusing on the oxidation of isoprene by the nitrate radical, NO\u2083, we find that reactions of peroxy radicals (RO\u2082) to form ROOR dimers is an important process in SOA formation. The other gas-phase products of these RO\u2082 reactions differ from what is expected from studies of simpler radicals, indicating that more studies are necessary to fully constrain RO\u2082 chemistry. Finally, we examine the role of heterogeneous oxidation as a sink of organic aerosol and a source of oxygenated volatile organic compounds in the free troposphere.", "doi": "10.7907/2ET7-0D89", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:6449", "collection": "thesis", "collection_id": "6449", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05262011-104023732", "primary_object_url": { "basename": "Hersey_Thesis_FinalSubmit_110525.pdf", "content": "final", "filesize": 44947049, "license": "other", "mime_type": "application/pdf", "url": "/6449/1/Hersey_Thesis_FinalSubmit_110525.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Studies of Aerosol Composition and Hygroscopicity", "author": [ { "family_name": "Hersey", "given_name": "Scott Patrick", "clpid": "Hersey-Scott-Patrick" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Sorooshian", "given_name": "Armin", "clpid": "Sorooshian-A" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Atmospheric aerosols have significant impacts on human health, regional visibility, and the radiative energy balance of Earth, but there remain many uncertainties about their sources and evolution in the atmosphere, as well as the details and magnitude of their impact on climate. This thesis introduces a novel instrument for measuring aerosol hygroscopicity, an important factor in the overall climate impact of aerosols, and presents results from several field campaigns and laboratory experiments aimed at characterizing the chemical composition and hygroscopicity of atmospheric particles.
\r\n\r\nAerosol water uptake determines particle size, which thereby determines an aerosol's scattering properties and radiative forcing. The Differential Sizing and Hygroscopicity Spectrometer Probe (DASH-SP) was designed to make rapid measurements of hygroscopicity on timescales short enough for aircraft deployment. Combined with an iterative data processing algorithm, the DASH-SP is demonstrated to accurately measure particle size, growth, and ``effective\" refractive index for particles from 135 nm to over 1 \u03bcm on timescales as short as a few seconds.
\r\n\r\nThe DASH-SP was deployed off the coast of Central California to measure aerosol water uptake in a marine atmosphere impacted by aged anthropogenic emissions. Composition data from an Aerosol Mass Spectrometer (AMS) indicates that organics are uniformly highly oxidized (O:C ratio = 0.92 \u00b1 0.33), and aerosol growth data from the DASH-SP indicates that in such a highly-oxidized environment, growth factor GF = Dp,wet/Dp,dry) can be accurately predicted as a simple function of relative humidity (RH) and organic volume fraction.
\r\n\r\nA major ground-based sampling study was carried out in Pasadena, CA, a receptor site for transported Los Angeles pollution, and was dubbed the Pasadena Aerosol Characterization Observatory (PACO). Results indicate that organics dominate transported Los Angeles aerosols, and that they are overwhelmingly oxidized in nature. Aerosol species tend to reside in distinct size modes, with inorganics typically found in larger, accumulation-mode aerosol, while semivolatile secondary organic aerosol (SV-OOA) products appear to reside predominantly in a fine mode. Hygroscopicity was found to be a strong function of organic mass fraction (OMF).
\r\n\r\nThe end of PACO sampling coincided with a major forest fire in Los Angeles County. The impact of this fire on the sampling site is explored by comparing water soluble organic carbon (WSOC) and organic mass-to-charge (m/z) markers from the AMS. In the absence of fire influence, WSOC concentrations are primarily driven by concurrent photochemistry and sea breeze transport from source-rich areas. Fire periods are characterized by significant primary production of WSOC and overnight/early morning transport of fire emissions to the sampling site.
\r\n\r\nFinally, DASH-SP results from the May 2010 CalNex field experiment indicate that aerosol hygroscopicity is determined primarily by the mass fraction of organics and nitrate in the aerosol. Overall hygroscopicity is very similar to that measured during PACO, though organics appear to be less hygroscopic during CalNex - likely because PACO represented transported, aged aerosol, while CalNex flights covered the entirety of the LA basin, including more source-rich areas.
", "doi": "10.7907/GZY7-P532", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:5874", "collection": "thesis", "collection_id": "5874", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282010-012507201", "primary_object_url": { "basename": "Manuj_thesis.pdf", "content": "final", "filesize": 5067713, "license": "other", "mime_type": "application/pdf", "url": "/5874/1/Manuj_thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "The Bulk Viscosity of Suspensions", "author": [ { "family_name": "Swaroop", "given_name": "Manuj", "clpid": "Swaroop-Manuj" } ], "thesis_advisor": [ { "family_name": "Brady", "given_name": "John F.", "clpid": "Brady-J-F" } ], "thesis_committee": [ { "family_name": "Brady", "given_name": "John F.", "clpid": "Brady-J-F" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Hunt", "given_name": "Melany L.", "clpid": "Hunt-M-L" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Particles suspended in a fluid are known to undergo variations in the local concentration in many flow situations; essentially a compression or expansion of the particle phase. The modeling of this behavior on a macroscopic scale requires knowledge of the effective bulk viscosity of the suspension, which has not been studied before. The bulk viscosity of a pure compressible fluid is defined as the constant of proportionality that relates the difference between the mechanical pressure and the thermodynamic pressure to the rate of compression. The bulk viscosity of a suspension is defined analogous to that for a pure fluid as the constant of proportionality relating the deviation of the trace of the macroscopic stress from its equilibrium value to the average rate of compression. The compression flow drives the suspension microstructure out of equilibrium and the thermal motion of the particles tries to restore equilibrium. The Peclet number (Pe), defined as the expansion rate made dimensionless with the Brownian time-scale, governs the departure of the microstructure from equilibrium. The microstructural forcing in compression is monopolar for small Pe resulting in a significantly slower spatial and temporal response of the microstructure compared to shearing or diffusive motion.
\r\n\r\nWe have determined the effective suspension bulk viscosity for all concentrations and all rates of compression, accounting for the full thermodynamic and hydrodynamic interactions that particles experience at the micro-scale. Current simulation techniques were enhanced to enable the dynamic simulation of compression flows in a suspension. A 'compression thinning' of the suspension is observed at small rates of compression and there is some 'compression thickening' at large compression rates. The bulk viscosity diverges as the volume fraction nears maximum packing and is in fact larger than the shear viscosity. Existing models for multiphase flows must therefore include the bulk viscosity term to properly simulate variations in particle concentration.
\r\n\r\nAn understanding of bulk viscosity effects in suspensions will enable the modeling of certain aggregation and separation behavior and lead to more accurate models for multiphase flows where there are variations in the particle concentration, such as filtration or fluidization.
", "doi": "10.7907/HQGZ-DV22", "publication_date": "2010", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:5471", "collection": "thesis", "collection_id": "5471", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12212009-151636210", "primary_object_url": { "basename": "Thesis_JC.pdf", "content": "final", "filesize": 3792814, "license": "other", "mime_type": "application/pdf", "url": "/5471/11/Thesis_JC.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Chemical Fractionation at Environmental Interfaces", "author": [ { "family_name": "Cheng", "given_name": "Jie", "clpid": "Cheng-Jie" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Chemical processes at the interfaces often differ kinetically and mechanistically from the bulk counterparts, partly due to the concentration inhomogeneity of different chemicals at the interfaces. The fractionation of chemicals at the interfaces not only determines their interfacial concentrations, but also affects the physicochemical properties of the interfaces. In this thesis, three sets of chemicals/interfaces with important environmental implications are studied: (1) anion fractionation at the gas\u2013liquid microdroplet interfaces, (2) fractionation of perfluoroalkyl surfactants and matrix components at the bubble\u2013water interface in ultrasonically irradiated solutions, and (3) ion fractionation across the ice\u2013water interface during the freeze\u2013thaw cycle of electrolyte solutions.
\r\n\r\nThe relative anion affinity for the air\u2013water interface, as measured by Electrospray Mass Spectrometry (ES\u2013MS), is exponentially correlated with ionic radius. The affinities respond differently to different additives, suggesting that specific anion effects are due to different energy levels of physical interactions. Relative anion affinities at the air\u2013methanol interfaces are almost identical to those at the air\u2013water interface, suggesting that surface structure is not the primary driving force for interfacial anion fractionation.
\r\n\r\nPerfluoroalkyl carboxylates and sulfonates can be transferred from the ocean to marine aerosols due to their high affinity for the air\u2013water interface, but transfer to gas phase is unlikely as they remain deprotonated in aqueous phase because of their low pKa. Organic matrix components may reduce the sonochemical kinetics of Perfluorooctanesulfonate (PFOS) and Perfluorooctanoate (PFOA) by competitive adsorption onto the bubble\u2013water interface or by lowering the interfacial temperatures. Inorganic anions, but not cations, may significantly enhance or reduce the sonochemical kinetics of PFOS and PFOA. The specific anion effects following the Hofmeister series are likely related to anions\u2019 partitioning to and interaction with the bubble\u2013water interface.
\r\n\r\nTime\u2013resolved confocal fluorescence microscopy of freezing electrolyte solutions reveals that the thickness of interstitial liquid films depends non\u2013monotonically on electrolyte concentration. It also confirms that selective incorporation of cations (anions) into the ice lattice decreases (increases) the pH of the interstitial liquid films. Since the magnitude of pH change during freezing is smaller than during the subsequent thawing process, it is likely to be limited by the seepage of proton or hydroxide slowly produced via water dissociation.
\r\n", "doi": "10.7907/08FV-FP25", "publication_date": "2010", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:5593", "collection": "thesis", "collection_id": "5593", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03122010-020001934", "type": "thesis", "title": "Analysis of the Chemical Composition of Atmospheric Organic Aerosols by Mass Spectrometry", "author": [ { "family_name": "Surratt", "given_name": "Jason Douglas", "orcid": "0000-0002-6833-1450", "clpid": "Surratt-Jason-Douglas" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Blake", "given_name": "Geoffrey A.", "clpid": "Blake-G-A" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Although secondary organic aerosol (SOA) makes up a substantial fraction of the organic mass observed in tropospheric fine particulate matter, there remain significant uncertainties in the true impact of atmospheric aerosols on climate and health due to the lack of full knowledge of the sources, composition, and mechanisms of formation of SOA. This thesis demonstrates how the detailed chemical characterization of both laboratory-generated and ambient organic aerosol using advanced mass spectrometric techniques has been critical to the discovery of previously unidentified sources (i.e., role heterogeneous chemistry) of SOA.
\r\n\r\nThe focal point of this thesis is given to the detailed chemical characterization of isoprene SOA formed under both high- and low-NOx conditions. Until recently, the formation of SOA from isoprene, the most abundant non-methane hydrocarbon emitted into the troposphere, was considered insignificant owing to the volatility of its oxidation products. In conjunction with the chemical characterization of gas-phase oxidation products, we identify the role of two key reactive intermediates, epoxydiols of isoprene (IEPOX) and methacryloylperoxynitrate (MPAN), that are formed during isoprene oxidation under low- and high-NOx conditions, respectively. Increased uptake of IEPOX by acid-catalyzed particle-phase reactions is shown to enhance low-NOx SOA formation. The similarity of the composition of SOA formed from the photooxidation of MPAN to that formed from isoprene and methacrolein demonstrates the role of MPAN in the formation of isoprene high-NOx SOA. More specifically, the further oxidation of MPAN leads to SOA by particle-phase esterification reactions. Reactions of IEPOX and MPAN in the presence of anthropogenic pollutants could be a substantial source of \"missing urban SOA\" not included in current SOA models.
\r\n\r\nIncreased aerosol acidity is found to result in the formation of organosulfates, which was a previously unrecognized source of SOA. By comparing the tandem mass spectrometric and accurate mass measurements collected for both the laboratory generated and ambient aerosol, previously uncharacterized ambient organic aerosol components are found to be organosulfates of isoprene, \u03b1 pinene, \u03b2 pinene, and limonene-like monoterpenes, demonstrating the ubiquity of organosulfate formation in ambient SOA. We estimate that the organosulfate contribution to the total organic mass fraction in certain locations could be substantial (upwards of 30%).
\r\n\r\n", "doi": "10.7907/PVWD-HZ44", "publication_date": "2010", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:5814", "collection": "thesis", "collection_id": "5814", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05182010-161102525", "primary_object_url": { "basename": "thesis_awhc.pdf", "content": "final", "filesize": 15871075, "license": "other", "mime_type": "application/pdf", "url": "/5814/1/thesis_awhc.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Chamber Studies and Modeling of Secondary Organic Aerosol Formation", "author": [ { "family_name": "Chan", "given_name": "Arthur Wing Hong", "orcid": "0000-0001-7392-4237", "clpid": "Chan-Arthur-Wing-Hong" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Secondary organic aerosol (SOA), formed from atmospheric oxidation of gas-phase hydrocarbons, comprise a large fraction of ambient particulate matter. Significant uncertainties exist in identifying the sources and mechanisms responsible for SOA formation, making it difficult to understand its impact on global climate and local air quality. Laboratory chambers have been a valuable tool to study underlying chemical mechanisms of SOA formation and to quantify SOA formation from select hydrocarbons in a controlled environment. However, a good understanding of the chemical processes involved is required to be able to extrapolate data acquired from smog chamber studies. This thesis presents results from experimental investigation of SOA formation from atmospherically important compounds, and model simulations of kinetic mechanisms involved in SOA formation.
\r\n\r\nThe distinguishing mechanism of SOA formation is the partitioning of semivolatile hydrocarbon oxidation products between the gas and aerosol phases. While SOA formation is typically described in terms of partitioning only, the rate of formation and ultimate yield of SOA can also depend on the kinetics of both gas- and aerosol-phase processes. Here a general equilibrium/kinetic model of SOA formation is presented to provide a framework for evaluating the extent to which the controlling mechanisms of SOA formation can be inferred from laboratory chamber data. Current atmospheric models systematically underpredict SOA formation, suggesting that in current models, 1) signicant SOA precursors could be missing and 2) SOA forming processes could be misrepresented. Aerosol formation from oxidation of 2-methyl-3-buten-2-ol (MBO) and polycyclic aromatic hydrocarbons (PAHs), two important classes of compounds previously assumed to be an insignicant SOA source, is studied. Upon photooxidation, MBO produces glyoxal (an important SOA intermediate), but the yields are too low to be atmospherically important. Photooxidation of napthalene and other 2-ring PAHs leads to substantial amounts of aerosol, and can account for a large fraction of SOA formed from oxidation of diesel exhaust and other primary emissions.
\r\n\r\nIsoprene is a signicant source of atmospheric organic aerosol; however, the oxidation pathways that lead to SOA have remained elusive. Under remote low-NOx conditions, epoxydiols are formed from gas-phase photooxidation of isoprene, and are found to undergo reactive uptake to lead to low-volatility compounds, such as C5-methyltetrols and organosulfates observed in ambient particulate matter. Under urban high-NOx conditions, methacrolein, an important C4 aldehyde formed from isoprene oxidation, is found to form SOA via reaction with NO2 to form peroxy methacryloyl nitrate, which subsequently forms low-volatility oligoester products. As a result of radical chemistry of aldehydes, SOA formation from isoprene depends critically on the NO2/NO ratio, and the implications on ambient aerosol formation are discussed.
", "doi": "10.7907/61XH-D105", "publication_date": "2010", "thesis_type": "phd", "thesis_year": "2010" }, { "id": "thesis:2272", "collection": "thesis", "collection_id": "2272", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05292009-113717", "primary_object_url": { "basename": "S_M_Murphy_Entire_Thesis.pdf", "content": "final", "filesize": 8734922, "license": "other", "mime_type": "application/pdf", "url": "/2272/9/S_M_Murphy_Entire_Thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Analysis of the Chemical Composition of Atmospheric and Chamber Generated Aerosol Using Mass Spectrometry", "author": [ { "family_name": "Murphy", "given_name": "Shane Michael", "orcid": "0000-0002-6415-2607", "clpid": "Murphy-Shane-Michael" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Jonsson", "given_name": "Haflidi H.", "clpid": "Jonsson-H-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis presents results demonstrating the use of particulate composition measurements to determine the mechanisms of aerosol formation in both chamber and field studies. Aerosol composition measurements are also used to theoretically estimate the water-uptake behavior and ability to nucleate cloud droplets of atmospheric aerosol; these estimates are compared with in-situ airborne measurements. Common to all studies presented is the use of online aerosol mass spectrometry, a technique with high time resolution and minimal artifacts.
\r\n\r\nChemical mechanisms involved in particle formation from the photooxidation of isoprene were explored in chamber studies using both online and offline mass spectrometry. The yield of aerosol and the nature of oliogmers formed was found to depend on the NOx concentration. Peroxides were found to be important under low-NOx conditions while under high-NOx conditions the majority of the particulate mass was found to derive from reaction products of methacrolein.
\r\n\r\nParticle formation from photooxidation of aliphatic amines was shown to be a feasible route of secondary organic aerosol formation in the atmosphere. Chamber studies at low relative humidity demonstrated that particle formation is primarily the result of acid-base reactions between amines and nitric or sulfuric acid, though diverse oxidized organic compounds are also formed. Thermodynamic calculations show that certain amines can compete with ammonia to form aminium salts at atmospherically relevant concentrations. An airborne field study near a major bovine source in the San Joaquin Valley, CA gave evidence of particulate amine formation in the atmosphere.
\r\n\r\nThe composition of particulate emissions from ships was studied during a joint shipboard and airborne field project in the Eastern Pacific. Particulate emissions were found to contain significantly higher levels of organic material than accounted for in current inventories. Observed hydrophobic organic material is concentrated in smaller particles and acts to suppress hygroscopic growth and activity of ship-exhaust particles as cloud condensation nuclei.
\r\n\r\nOngoing research involves quantifying the impact of reactions within cloud droplets on the organic composition of aerosols. A recently completed field campaign investigated the role of particle chemistry in determining if aerosols can act as ice crystal nuclei.
\r\n", "doi": "10.7907/6B9K-AT89", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:5060", "collection": "thesis", "collection_id": "5060", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12182008-174607", "primary_object_url": { "basename": "Thesis_2side.pdf", "content": "final", "filesize": 16076250, "license": "other", "mime_type": "application/pdf", "url": "/5060/1/Thesis_2side.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. Global Simulations of Interactions between Aerosols and Future Climate and II. Sensitivity of Multiangle Imaging to the Optical and Microphysical Properties of Biomass Burning Aerosols", "author": [ { "family_name": "Chen", "given_name": "Wei-Ting", "orcid": "0000-0002-9292-0933", "clpid": "Chen-Wei-Ting" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Schneider", "given_name": "Tapio", "clpid": "Schneider-T" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "To understand the interaction between aerosols and climate, equilibrium simulations with a general circulation model are carried out in Part I to study the effects of future climate change on aerosol distributions, as well as the climate responses to future aerosol changes. The predicted warmer climate induced by carbon dioxide modifies the climate-sensitive emissions, alters the thermodynamic partitioning, and enhances wet removal of the aerosols. The direct radiative perturbations of aerosols, and the modification of clouds by aerosols can potentially change the temperature distribution, the hydrological cycle, and the atmospheric circulation; the pattern of climatic impacts from aerosols are differentiated from those of anthropogenic greenhouse gases. In Part II, the aerosol retrieval algorithm of the remote sensing instrument, the Multi-angle Imaging SpectroRadiometer (MISR), is assessed for the retrieval of biomass burning aerosols. By comparisons with coincident ground measurements and theoretical sensitivity tests, specific refinements to particle and mixture properties assumed in the algorithm for biomass burning aerosols are proposed. Representative case studies confirm the theoretical results and underline the key role of surface characterization in the remote sensing of aerosols.", "doi": "10.7907/0ZWE-9K94", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:1653", "collection": "thesis", "collection_id": "1653", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05062008-111214", "primary_object_url": { "basename": "Vijay_Thesis.pdf", "content": "final", "filesize": 22198958, "license": "other", "mime_type": "application/pdf", "url": "/1653/1/Vijay_Thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Radiative Transfer Modeling for the Retrieval of CO\u2082 from Space", "author": [ { "family_name": "Natraj", "given_name": "Vijay", "orcid": "0000-0003-3154-9429", "clpid": "Natraj-Vijay" } ], "thesis_advisor": [ { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "thesis_committee": [ { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The Orbiting Carbon Observatory (OCO) mission was proposed to deliver the first temporally and spatially resolved global observations of CO2 to improve our understanding of the sources and sinks of CO\u2082. A retrieval algorithm was developed to obtain the column-averaged dry-air mixing ratio of CO\u2082 (XCO\u2082) from spectroscopic measurements of absorption in the 0.76 \u00b5m O2 A band and two near-infrared (NIR) bands of CO\u2082 centered at 1.61 \u00b5m and 2.06 \u00b5m. An aerosol optical-property database was developed to aid with the retrievals. Principal-component analysis was used to speed up radiative transfer (RT) computations. To test the algorithm, column O\u2082 was retrieved from measurements of absorption in the O2 A band over the sea surface. Using a single sounding, the column O\u2082 was retrieved with an error of around 1%. Polarization was shown to have a significant impact on the retrieval-error budget. A new model based on computing two orders of scattering (2OS) was developed to compute polarization in the OCO spectral regions. The multiple-scattering, scalar model Radiant was combined with the 2OS model to create the R-2OS OCO RT model. Tests with simulated backscatter measurements at the OCO validation sites showed that the R-2OS model reduced the biases in retrieved XCO\u2082 to much lower than 1 ppm in most scenarios, compared to errors as high as 10 ppm using the scalar model. Aerosol vertical distribution, thin cirrus and surface bidirectional reflection need further study.\r\n", "doi": "10.7907/XSPZ-5F22", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:1666", "collection": "thesis", "collection_id": "1666", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05072008-174726", "primary_object_url": { "basename": "Sorooshian_thesis.pdf", "content": "final", "filesize": 13469968, "license": "other", "mime_type": "application/pdf", "url": "/1666/1/Sorooshian_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Aerosol Composition and Hygroscopicity Studies: Instrument Development/Characterization, Ambient and Laboratory Measurements, and Modeling", "author": [ { "family_name": "Sorooshian", "given_name": "Armin", "orcid": "0000-0002-2243-2264", "clpid": "Sorooshian-Armin" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Jonsson", "given_name": "Haflidi H.", "clpid": "Jonsson-H-H" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Aerosols influence climate by altering the global energy balance via scattering and absorbing solar radiation (direct effects), and by their effect on the reflectance of clouds and occurrence of precipitation (indirect effects). Aerosols also influence biogeochemical cycles, lead to diminished environmental visibility, and harm human health. This thesis focuses on advancing knowledge of critical properties, specifically composition and hygroscopicity, which govern the role of aerosols in climatic and environmental change. The methods used in this work include a combination of instrument development/characterization, ambient and laboratory measurements, and modeling.
\r\n\r\nAn instrument was developed to quantify the water-soluble composition of aerosols. The particle-into-liquid sampler (PILS) grows ambient particles into droplets that grow sufficiently large to be collected by inertial impaction. After being collected in vials, the liquid sample can be analyzed with a variety of analytical methods including ion chromatography. Results from characterization tests are presented, which summarize instrument accuracy, precision, size and time resolution, and uncertainties. An instrument model was developed to simulate operation of the PILS; the model considers plumbing transmission efficiencies, droplet growth, mixing effects, and volatilization losses. Model predictions and measurements are compared and are shown to exhibit good agreement.
\r\n\r\nA second instrument, termed the differential aerosol sizing and hygroscopicity spectrometer probe (DASH-SP), was developed to quantify aerosol hygroscopic growth and refractive index. This technique employs size classification of dry aerosol particles, equilibrates the classified particles to multiple relative humidities, and then measures the sizes of the grown particles using optical particle counters. Similar to the PILS, results from an extensive set of characterization test are presented. DASH-SP measurements of growth factor for various inorganic and organic acid salts are reported and compared to thermodynamic predictions.
\r\n\r\nAirborne aerosol measurements from four separate field campaigns are presented. The main topics of investigation from the ambient experiments include the following: (1) in-cloud production of secondary organic aerosol; (2) a characterization of the sources and character of water-soluble aerosol composition during the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS); and (3) a comprehensive airborne characterization of aerosol from a massive bovine source.
\r\n", "doi": "10.7907/FMCM-4Q81", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:1927", "collection": "thesis", "collection_id": "1927", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05212008-152946", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 4166770, "license": "other", "mime_type": "application/pdf", "url": "/1927/1/thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "High-Resolution Study of the O\u2082 A-Band using Frequency Stabilized Cavity Ring-Down Spectroscopy", "author": [ { "family_name": "Robichaud", "given_name": "David Joseph", "orcid": "0000-0002-8925-9013", "clpid": "Robichaud-David-Joseph" } ], "thesis_advisor": [ { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Chen", "given_name": "Pin", "clpid": "Chen-Pin" } ], "thesis_committee": [ { "family_name": "Blake", "given_name": "Geoffrey A.", "clpid": "Blake-G-A" }, { "family_name": "Miller", "given_name": "Charles E.", "clpid": "Miller-C-E" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "clpid": "Beauchamp-J-L" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis describes laboratory measurements of the O\u2082 A-band spectrum using frequency stabilized cavity ring-down spectroscopy (FS-CRDS). The FS-CRDS allowed the collection of high-resolution (<1 MHz) spectra in conjunction with the exception sensitivity of the CRDS technique. Line positions were measured with an accuracy better than 2 x 10 \u207b\u2075 cm \u207b\u00b9 by calibrating our spectra against the hyperfine components of \u00b3\u2079K D lines. Line parameters were determined using a variety of lineshape models from the standard Voigt profile to models incorporating speed dependence and collisional narrowing. Clear deviations are shown between the observed and Voigt profiles, while the other profiles considered were found to fit the observed lineshapes well. Line intensities obtained using the Galatry profile are compared with previously measured values and found to be approximately 1% smaller than intensities found in current databases. Many of the other lineshape parameters are in good agreement with previous measurements. However, the pressure-induced shifts of the current work are considered much more accurate than other studies. Finally we report on the line parameters of each of the isotopologues of O\u2082. ", "doi": "10.7907/Q6GB-R592", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:3588", "collection": "thesis", "collection_id": "3588", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09172007-160334", "primary_object_url": { "basename": "ch1_title_introduction.pdf", "content": "final", "filesize": 385123, "license": "other", "mime_type": "application/pdf", "url": "/3588/1/ch1_title_introduction.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Thermodynamic Modeling of Organic Aerosol", "author": [ { "family_name": "Tong", "given_name": "Chinghang", "clpid": "Tong-Chinghang" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Goddard", "given_name": "William A., III", "clpid": "Goddard-W-A-III" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Blanco", "given_name": "Mario", "clpid": "Blanco-M" }, { "family_name": "Okumura", "given_name": "Mitchio", "clpid": "Okumura-M" }, { "family_name": "Goddard", "given_name": "William A., III", "clpid": "Goddard-W-A-III" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Modeling atmospheric aerosols containing a large organic fraction with unknown chemical composition and properties has been a constant challenge. The dissertation focuses on the theoretical treatment of the thermodynamic equilibrium of atmospheric aerosol involving organic species.
\r\n\r\nWe present a vapor pressure estimation method, based on quantum chemistry methods, to predict the liquid vapor pressure, enthalpies of vaporization, and heats of sublimation of atmospheric organic compounds. Predictions are compared to literature data, and the overall accuracy is considered satisfactory given the simplicity of the equations. Quantum mechanical methods were also used to investigate the thermodynamic feasibility of various acid-catalyzed aerosol-phase heterogeneous chemical reactions. A stepwise procedure is presented to determine physical properties such as heats of formation, standard entropies, Gibbs free energies of formation, and solvation energies from quantum mechanics, for various short-chain aldehydes and ketones. Equilibrium constants of hydration reactions and aldol condensation are then reported; predictions are in qualitatively agreement with previous studies. We have shown that quantum methods can serve as useful tools for first approximation, especially for species with no available data, in determining the thermodynamic properties of multifunctional oxygenates.
\r\n\r\nWe also present an atmospheric aerosol phase equilibrium model to determine the aerosol phase equilibrium of aqueous systems. Phase diagrams for a number of organic/water systems characteristic of both primary and secondary organic aerosols are computed. Effects of organics on the deliquescence behavior of electrolytes are also shown in the inorganic/organic/water phase diagrams.
\r\n\r\nFinally, we evaluate the performance of four recent activity coefficient models developed for inorganic-organic-water mixtures typical of atmospheric aerosols. Based on the comparison on water activities, it is found that models that include ion-organic mixture parameters (referred to as coupled models) do not necessarily produce more accurate predictions than those models that utilizes additive approaches (referred to as decoupled models). Since the chemical composition and physical properties of the organic fraction is largely unknown, the additive approaches of the decoupled models are more feasible than the coupled model.
\r\n", "doi": "10.7907/3M7R-9620", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:1962", "collection": "thesis", "collection_id": "1962", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05222008-234331", "primary_object_url": { "basename": "Thesis_revised.pdf", "content": "final", "filesize": 34880122, "license": "other", "mime_type": "application/pdf", "url": "/1962/1/Thesis_revised.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Remote Sensing of Radiative Fluxes and Heating Rates from Satellite Instrument Measurements", "author": [ { "family_name": "Feldman", "given_name": "Daniel Robert", "orcid": "0000-0003-3365-5233", "clpid": "Feldman-Daniel-Robert" } ], "thesis_advisor": [ { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Liou", "given_name": "Kuo-Nan", "clpid": "Liou-K" }, { "family_name": "Schneider", "given_name": "Tapio", "clpid": "Schneider-T" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Weather and climate models are required to calculate radiative fluxes and shortwave heating and longwave cooling rate profiles on a large scale. Heating and cooling rates describe the effect that different configurations of temperature, radiatively active gases, and clouds have on the rates of interlayer energy exchange and affect circulation patterns. Meanwhile, a suite of satellite-based instruments from the NASA Earth Observing System\u2019s A-Train provide an unprecedented set of measurements that can be used to produce quantities that can also yield radiative fluxes and heating and cooling rates. This work explores the extent to which passive-infrared hyperspectral measurements such as those made by the Atmospheric Infrared Sounder impart information towards infrared cooling rates. Several novel methods are explored for interpreting and retrieving cooling rates using spectral measurements.
\r\n\r\nFor scenes with optically thick clouds, however, passive visible and infrared measurements will have limited power in describing heating and cooling rates. Vertical cloud information can be obtained from several A-Train instruments: the Microwave Limb Sounder Ice Water Content product provides data on the profiles of ice clouds in the upper troposphere and this work explores how this data can be used to describe the cloud radiative effect. Recently, active-sounding measurements from CloudSat have offered an unrivalled description of cloud profiles which can be used to compute fluxes and heating rates. Preliminary CloudSat products are evaluated and a case study of heating rate analysis is presented in which CloudSat products are used to determine Tropical Tropopause Layer radiation balance.
\r\n\r\nThe radiative processes that affect the far-infrared (wavelengths of 15\u2013100 \u03bcm) are described in a limited fashion by the current suite of A-Train measurements, and yet these spectral regions have a large impact on cooling rates in the troposphere. The extra information gained by the introduction of a set of spectrally resolved far-infrared measurements is discussed for clear and cloudy scenes.
\r\n\r\nFinally, this work discusses future directions for analyzing heating rates derived from remote sensing measurements, and challenges and opportunities for future research.
\r\n", "doi": "10.7907/XMMC-F033", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:613", "collection": "thesis", "collection_id": "613", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02122007-130627", "primary_object_url": { "basename": "Khair_thesis.pdf", "content": "final", "filesize": 6449685, "license": "other", "mime_type": "application/pdf", "url": "/613/1/Khair_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Particle Motion in Colloidal Dispersions: Applications to Microrheology and Nonequilibrium Depletion Interactions", "author": [ { "family_name": "Khair", "given_name": "Aditya Satish", "orcid": "0000-0001-6076-2910", "clpid": "Khair-Aditya-Satish" } ], "thesis_advisor": [ { "family_name": "Brady", "given_name": "John F.", "clpid": "Brady-J-F" } ], "thesis_committee": [ { "family_name": "Brady", "given_name": "John F.", "clpid": "Brady-J-F" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Squires", "given_name": "Todd M.", "clpid": "Squires-T-M" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "clpid": "Wang-Zhen-Gang" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Over the past decade, microrheology has burst onto the scene as a technique to interrogate and manipulate complex fluids and biological materials at the micro- and nano-meter scale. At the heart of microrheology is the use of colloidal 'probe' particles embedded in the material of interest; by tracking the motion of a probe one can ascertain rheological properties of the material. In this study, we propose and investigate a paradigmatic model for microrheology: an externally driven probe traveling through an otherwise quiescent colloidal dispersion. From the probe's motion one can infer a 'microviscosity' of the dispersion via application of Stokes drag law. Depending on the amplitude and time-dependence of the probe's movement, the linear or nonlinear (micro-)rheological response of the dispersion may be inferred: from steady, arbitrary-amplitude motion we compute a nonlinear microviscosity, while small-amplitude oscillatory motion yields a frequency-dependent (complex) microviscosity. These two microviscosities are shown, after appropriate scaling, to be in good agreement with their (macro)-rheological counterparts. Furthermore, we investigate the role played by the probe's shape --- sphere, rod, or disc --- in microrheological experiments.
\r\n\r\nLastly, on a related theme, we consider two spherical probes translating in-line with equal velocities through a colloidal dispersion, as a model for depletion interactions out of equilibrium. The probes disturb the tranquility of the dispersion; in retaliation, the dispersion exerts a entropic (depletion) force on each probe, which depends on the velocity of the probes and their separation. When moving 'slowly' we recover the well-known equilibrium depletion attraction between probes. For 'rapid' motion, there is a large accumulation of particles in a thin boundary layer on the upstream side of the leading probe, whereas the trailing probe moves in a tunnel, or wake, of particle-free solvent created by the leading probe. Consequently, the entropic force on the trailing probe vanishes, while the force on the leading probe approaches a limiting value, equal to that for a single translating probe.
", "doi": "10.7907/RWKF-E288", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:2031", "collection": "thesis", "collection_id": "2031", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05242007-210716", "primary_object_url": { "basename": "THESIS.pdf", "content": "final", "filesize": 10395195, "license": "other", "mime_type": "application/pdf", "url": "/2031/20/THESIS.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Chamber Studies of Secondary Organic Aerosol Formation", "author": [ { "family_name": "Ng", "given_name": "Nga Lee", "orcid": "0000-0001-8460-4765", "clpid": "Ng-Nga-Lee" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Atmospheric oxidation of volatile organic compounds leads to the formation of secondary organic aerosol (SOA). Laboratory chambers provide a controlled environment for investigating aerosol formation and evolution. This thesis presents results on aerosol formation from a wide range of parent organic compounds under a variety of experimental conditions.
\r\n\r\nThe effect of particle-phase acidity on aerosol formation is explored in a series of alkene ozonolysis experiments. Oligomeric species are detected regardless of the particle-phase acidity, indicating the ubiquitous existence of particle-phase reactions. As acidity increases, larger oligomers are formed more abundantly and aerosol yields also increase. Volatile organic compounds generally not considered to be SOA precursors, including isoprene and glyoxal, have been shown to lead to aerosol formation. Uptake of glyoxal into particles is evidence that small molecules can potentially produce aerosol via reactive absorption. Although there is strong evidence that heterogeneous reactions play an important role in SOA formation, the detailed mechanisms remain poorly understood. In a comprehensive study on aerosol formation from biogenic hydrocarbons, it is found that data on aerosol growth as a function of the amount of hydrocarbon reacted provide important insights into the general aerosol formation mechanisms by identifying rate-determining steps and whether SOA is formed from first- or second-generation products.
\r\n\r\nThe mechanism of aerosol formation by isoprene is specifically investigated over a range of NOx concentrations. Aerosol yields are found to decrease substantially with increasing NOx. The same NOx dependence is observed for monoterpenes ([alpha]-pinene), as well as aromatic hydrocarbons (m-xylene, toluene, and benzene). It is suggested that peroxy radical chemistry plays the central role in the observed NOx dependence. The NOx dependence for larger compounds is, however, different from that of isoprene, monoterpenes, and aromatics. For sesquiterpenes such as longifolene and aromadendrene, aerosol yields increase with increasing NOx concentration. The reversal of the NOx dependence of SOA formation for the sesquiterpenes appears to be the result of formation of relatively nonvolatile organic nitrates, and/or the isomerization of large alkoxy radicals that leads to less volatile products.
", "doi": "10.7907/XFEN-5Q08", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:2339", "collection": "thesis", "collection_id": "2339", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05312007-133239", "primary_object_url": { "basename": "henze_thesis_final.pdf", "content": "final", "filesize": 15015624, "license": "other", "mime_type": "application/pdf", "url": "/2339/1/henze_thesis_final.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Forward and Inverse Analysis of Chemical Transport Models", "author": [ { "family_name": "Henze", "given_name": "Daven Ker", "orcid": "0000-0001-6431-4963", "clpid": "Henze-Daven-Ker" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Li", "given_name": "Qinbin", "clpid": "Li-Q" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Schneider", "given_name": "Tapio", "clpid": "Schneider-T" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Assessing the discrepancy between modeled and observed distributions of aerosols is a persistent problem on many scales. Tools for analyzing the evolution of aerosol size distributions using the adjoint method are presented in idealized box model calculations. The ability to recover information about aerosol growth rates and initial size distributions is assessed given a range of simulated observations of evolving systems. While such tools alone could facilitate analysis of chamber measurements, improving estimates of aerosol sources on regional and global scales requires explicit consideration of many additional chemical and physical processes that govern secondary formation of atmospheric aerosols from emissions of gas-phase precursors. The adjoint of the global chemical transport model GEOS-Chem is derived, affording detailed analysis of the relationship between gas-phase aerosol precursor emissions (SOx, NOx, and NH3) and the subsequent distributions of sulfate - ammonium - nitrate aerosol. Assimilation of surface measurements of sulfate and nitrate aerosol is shown to provide valuable constraints on emissions of ammonia. Adjoint sensitivities are used to propose strategies for air quality control, suggesting, for example, that reduction of SOx emissions in the summer and NH3 emissions in the winter would most effectively reduce non-attainment of aerosol air quality standards. The ability of this model to estimate global distributions of carbonaceous aerosol is also addressed. Based on new yield data from environmental chamber studies, mechanisms for incorporating the dependence of secondary organic aerosol (SOA) formation on NOx concentrations are developed for use in global models. When NOx levels are appropriately accounted for, it is demonstrated that sources such as isoprene and aromatics, previously neglected as sources of aerosol in global models, significantly contribute to predicted SOA burdens downwind of polluted areas (owing to benzene and toluene) and in the free troposphere (owing to isoprene).", "doi": "10.7907/5647-T777", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:4688", "collection": "thesis", "collection_id": "4688", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11292006-181629", "primary_object_url": { "basename": "Chapter_0_Title_Abstract_Table_of_Contents.pdf", "content": "final", "filesize": 122793, "license": "other", "mime_type": "application/pdf", "url": "/4688/1/Chapter_0_Title_Abstract_Table_of_Contents.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Photochemistry of Pyruvic Acid in Water and Ice", "author": [ { "family_name": "Guzm\u00e1n", "given_name": "Marcelo Ioel", "orcid": "0000-0002-6730-7766", "clpid": "Guzm\u00e1n-Marcelo-Ioel" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The 321 nm band photodecarboxylation of aqueous pyruvic acid, PA, solutions was studied in the range 5 \u2264 [PA] \u2264 100 mM. Prompt and delayed CO\u2082 production stages are detected using TEMPO as a scavenger. These two processes are resolved in the photolysis of frozen solutions: after simultaneous evolution during illumination, additional CO\u2082 is quantified in the dark (E\u2090 ~ 22 kJ mol\u207b\u00b9, T < 268 K). Photodecarboxylation rates of deareated aqueous PA solutions drop a two-fold in the frozen state at 253 K relative to the fluid at 293 K. Benzoylformic acid frozen solutions decarboxylate with no post-illumination CO\u2082 emissions.
\r\n\r\n\u00b9H-NMR studies of the hydration of aqueous PA between the carbonyl and its hydrated gem-diol species in the frozen state indicate that the fraction of the carbonyl-form of PA, approaches ~ 20% at temperatures below 263 K, regardless of the initial PA concentration in the range 0.1 M \u2264 [PA] \u2264 4.6 M. PA is cooperatively hydrated while dissolved in increasingly viscous aqueous microfluids often called quasi liquid layers (QLL) down to vitrification.
\r\n\r\nElectron magnetic resonance signals found in frozen aqueous PA solutions UV-irradiated at 77 K correspond to distant triplet radical pairs separated by ~ 0.9 nm. They originate by photoinduced electron transfer between a triplet excited state PA and ground state PA to produce \u00b3[PA\u207a\u22c5 PA\u207b\u22c5]. The subsequent deprotonation of PA\u207a\u22c5 into an acylcarbonyloxyl radical that undergoes ultrafast decarboxylation accounts for the unquenchable source of CO\u2082, even at cryogenic temperatures. Liquid chromatography with UV and ESI-MS detection in combination with \u00b9\u00b3C-isotope labeling experiments were used for products identification. The fate of the radical anion PA\u207b\u22c5 after protonation into a ketyl-radical is recombination into 2,3-dimethyltartaric acid or addition to a second PA molecule. The later process leads to an unstable 2-oxodicarboxylic acid that eliminates CO\u2082 to produce 2-(3-oxobutan-2-yloxy)-2-hydroxypropanoic.
\r\n\r\nIn conclusion, the possibility of photolysis in ice core records due to penetrating Cerenkov radiation derived from cosmic rays is explored. Potential impacts of the photolysis of organic matter trapped in ice with the subsequent release of CO and CO\u2082 over the last two millennia is analyzed.
", "doi": "10.7907/6CDJ-VD20", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:2107", "collection": "thesis", "collection_id": "2107", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05262006-115411", "primary_object_url": { "basename": "T_Rissman_PhD_Thesis.pdf", "content": "final", "filesize": 14041184, "license": "other", "mime_type": "application/pdf", "url": "/2107/1/T_Rissman_PhD_Thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Theory, Field Measurements, and Laboratory Experiments Concerning the Cloud Condensation Nucleus Properties of Organic and/or Insoluble Aerosol Components", "author": [ { "family_name": "Rissman", "given_name": "Tracey Alayne", "clpid": "Rissman-Tracey-Alayne" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Jonsson", "given_name": "Haflidi H.", "clpid": "Jonsson-H-H" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Predicting how the future climate of Earth will change as a result of increasing human emissions is one of the greatest problems facing science today. The earth\u2019s climate is the result of a delicate balance between incoming and outgoing radiation. Anthropogenic emissions of aerosol particles into the atmosphere have the potential to affect the earth\u2019s climate in significant ways through both direct and indirect effects on the earth\u2019s radiative balance. One of the largest uncertainties in aerosol radiative forcing is associated with the relationship between atmospheric aerosols and cloud formation, properties, and lifetime. Clouds form by water condensing on small particles (aerosols) in the air (referred to as cloud condensation nuclei, or CCN), and how the increasing levels of atmospheric particles will affect Earth\u2019s clouds and its hydrologic cycle represents one of the key problems in the science of climate. Through theoretical, field, and laboratory investigations, the results presented here reinforce the importance of atmospheric aerosol chemical composition in determining the ability of an aerosol particle to act as a CCN. A study that incorporates surface tension and limited solubility effects, especially of organic compounds, in parameterizations of cloud droplet activation indicate that these chemical effects can rival those of the meteorological environment. An inverse CCN/aerosol closure study of field measurements indicates that assumptions of simple chemistry and mixing state in the interpretation and analysis of field cloud condensation nuclei (CCN) measurements may not necessarily be sufficient and/or realistic, depending heavily on the location of the field study. Properties of organic compounds, such as functional groups, extent of dissociation, and solubility were found to influence the CCN activity of the compounds in laboratory experiments with pure organic aerosols. However, the importance of careful planning of laboratory experiments, in consideration of the properties of the organic compounds, was reinforced and results were carefully interpreted to avoid experimental bias in the conclusions.", "doi": "10.7907/FEP1-P208", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:3768", "collection": "thesis", "collection_id": "3768", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09252008-110728", "primary_object_url": { "basename": "Holunga_dm_2006.pdf", "content": "final", "filesize": 61571210, "license": "other", "mime_type": "application/pdf", "url": "/3768/1/Holunga_dm_2006.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Aerosol Technologies for Fabrication, Collection, and Deposition of Engineered Nanoparticles", "author": [ { "family_name": "Holunga", "given_name": "Dean Marcu", "orcid": "0000-0003-1101-2448", "clpid": "Holunga-Dean-Marcu" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Giapis", "given_name": "Konstantinos P.", "clpid": "Giapis-K-P" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "We demonstrate a turbulent mixing reactor capable of producing highly monodisperse, \u03c3G \u2248 1.1, heterogeneous oxide-coated silicon nanoparticles from pyrolytic decomposition of silane. Particle concentrations approach 10\u2079 cm\u207b\u00b3 as measured with a radial differential mobility analyzer and fA resolution electrometer. Turbulent mixing power, induced by locally high-momentum jets that actually remain below turbulent Reynolds numbers, induce mechanical mixing within a pathlength comparable to the diameter of the major flow channel. Timescales for transport are enhanced orders of magnitude above laminar processes, enabling nanoparticle evolutionary processes such as densification and crystallization to complete in the absence of significant agglomeration. Use of multiple jets in series may well enable the homogeneous introduction of additional reagents to facilitate additional heterogenous particle development.
\r\n\r\nParticles formed in the Inconel reactor were further studied using both transmission electron microscopy and photoluminescence measurements. Spherical particle morphology with faceted and unfaceted crystalline cores were observed, and thermal oxides appeared uniform. Particle purity and a high quality passivation of the particles were demonstrated by photoluminescence, although particles occasionally required additional processing to complete O\u2082 passivation. Photoluminescence measurements are in good agreement with models of quantum-confined exciton recombination, both in emitted wavelength and photoluminescence decay. Particle contamination studies using Electron Energy Loss Spectroscopy and Energy Dispersive X-Ray Spectroscopy found no evidence of metal contamination within particles studied for both native oxide and thermal oxide-coated particles. A phenomenological comparison of size information from the radial differential mobility analyzer and photoluminescence spectra demonstrated that thermally grown oxide shells and native oxide shell have initially opposite trends in the variation of thickness with particle size, although over time, native oxide shells thicken considerably.
\r\n\r\nA thermophoretic deposition chamber was designed for uniform deposition on wafers ranging in size from 100 mm\u2013300 mm and over a range of flowrates from 500 sccm to 15000 sccm. A power-law hyperbolic inlet nozzle was shown theoretically to minimize separation. A uniform axial temperature gradient is developed using programmable temperature controlled heaters along with active cooling. Characterization by atomic force microscopy studies on 150 mm wafers demonstrated uniform coverage both radially and in the azimuth, in good agreement with model results. Deposition uniformity is predicted on larger wafers, up to 300 mm.
\r\n\r\nPyrolysis reactions in small diameter tubular reactors foul the reactors\u2019 walls continuously, with deposition morphology ranging from thin-films to dendritic, filter-like structures. The particle number concentration decays linearly with time. Hybridization of the turbulent mixing reactor with high energy seed reactors, such as a microplasma discharge, shows promise that may significantly reduce fouling, maintain or increase particle number concentration, maintain or increase particle monodispersity, expand chemistries available, and retain the ability to produce heterogeneous particles.
\r\n\r\nLaminar flow reactors are well suited to the production of monodisperse, \u03c3G \u2248 1.1, aerosols. The rate of pyrolytic decomposition of silane precursor is kept relatively slow during a gentle thermal ramp wherein the low temperature favors vapor deposition growth over additional nucleation. The resulting reduction in silane inhibits further nucleation as the temperature is increased. Slow flowrates, wherein diffusional losses of precursor assists the inhibition of additional nucleation, also contributed to maintaining lower nucleation rates, but are not necessary to achieve monodispersity or higher yield.
\r\n\r\n", "doi": "10.7907/42Z7-PY73", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:2013", "collection": "thesis", "collection_id": "2013", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05242006-175333", "primary_object_url": { "basename": "01_Title_Intro.pdf", "content": "final", "filesize": 278851, "license": "other", "mime_type": "application/pdf", "url": "/2013/1/01_Title_Intro.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Ambient and Laboratory Studies of Aerosol Size Distributions and Hygroscopicity", "author": [ { "family_name": "Varutbangkul", "given_name": "Varuntida", "clpid": "Varutbangkul-Varuntida" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Jonsson", "given_name": "Haflidi H.", "clpid": "Jonsson-H-H" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The optical properties, health effects, atmospheric lifetime, and climate impact of ambient aerosols are influenced directly by their size distribution, chemical composition, and phase. The aerosol hygroscopicity, which is also a function of composition, governs the size and phase changes of these particles when subjected to varying ambient relative humidities (RH). This thesis presents results from a wide variety of studies involving laboratory and ambient measurements of aerosol size distributions and water uptake properties in the subsaturated regime. Time evolutions of particle size and hygroscopic growth were investigated for various secondary organic aerosol (SOA) systems generated in a smog chamber from ozonolysis of cycloalkenes and photooxidation of biogenic terpenes. SOA yields were measured at various initial parent hydrocarbon concentrations and correlated with the structure of the parent compound. The amount of water uptake of the aerosol at a reference RH was found to inversely correlate with the SOA yield. The hygroscopicity of many atmospherically relevant pure organic species was also studied using an unconventional particle generation scheme employing a nonaqueous solution. Experimental results were compared with predictions from an equilibrium thermodynamic model. In these works, organic aerosols are shown to exhibit complex hygroscopic growth, dependent on the particle chemistry, phase, and surrounding RH. Implications of the experimental techniques used on the observation of particle growth, deliquescence, and efflorescence are discussed. A number of other studies incorporating aircraft-based measurements of aerosol size distributions and hygroscopicity with other ambient measurements into various cloud microphysics models are also presented.", "doi": "10.7907/KQ8A-2Q95", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:2111", "collection": "thesis", "collection_id": "2111", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05262006-133416", "primary_object_url": { "basename": "APOThesis.pdf", "content": "final", "filesize": 3586495, "license": "other", "mime_type": "application/pdf", "url": "/2111/1/APOThesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Scanning Activity Gravimetric Analysis (SAGA) of Aqueous Polyethylene Oxide", "author": [ { "family_name": "Olsen", "given_name": "Adam Paul", "clpid": "Olsen-Adam-Paul" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Kornfield", "given_name": "Julia A.", "clpid": "Kornfield-J-A" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Kornfield", "given_name": "Julia A.", "clpid": "Kornfield-J-A" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "clpid": "Wang-Zhen-Gang" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis introduces a new technique\u2014scanning activity gravimetric analysis (SAGA)\u2014for investigating phase transitions in semicrystalline polymers. Isothermal growth and dissolution of polymer crystallites within picogram to milligram samples are manifested by mass changes in response to changes in the activity of sorbed solvent vapor. Single charged particles are levitated and weighed in an electrostatic field, providing access to highly supersaturated states. Phase transitions are inferred from simultaneous equilibrium sorption and light scattering measurements. Analogous to differential scanning calorimetry, scanning solvent activity up and down exposes broad transitions between the semicrystalline solid state and the dissolved state, which are influenced by sample history. We demonstrate dissolution and crystallization of nanogram samples of polyethylene oxide by controlling the activity of sorbed water vapor and observe self-nucleation of crystallites from partially states and fully dissolved states.
\r\n\r\nMemory effects in semicrystalline polymers have been documented for a variety of systems in which the rate of crystallization depends on the temperature and duration of a prior melting step. We report analogous observations of memory effects in aqueous solution droplets of polyethylene oxide. Remnants of the crystalline phase\u2014clusters of chain folded molecules\u2014that are too small to be detected by gravimetric or optical means persist for long times in solution after macroscopic crystals have been dissolved, and they then serve as athermal nuclei when the concentration of the polymer solution droplet is increased. These remnants evolve under certain conditions toward increasing or decreasing thickness, as indicated by a shift in the conditions at which they effectively catalyze crystal growth. Although memory effects in semicrystalline polymers have usually been attributed exclusively to sluggish kinetics of melting or dissolution, thermodynamic considerations may also play an important role. A simple model describing the free energy of a lamellar crystal based on insights of Janeschitz-Kriegl captures the metastability of lamellar remnants and their evolution in thickness. The qualitative successes of the model lend support to the thermodynamic rationalization of memory effects in semicrystalline polymers.
", "doi": "10.7907/5X91-2F81", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:975", "collection": "thesis", "collection_id": "975", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03172005-152448", "primary_object_url": { "basename": "MLLu2004thesis.pdf", "content": "final", "filesize": 4041803, "license": "other", "mime_type": "application/pdf", "url": "/975/2/MLLu2004thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Large-Eddy Simulations of Marine Cumulus and Stratocumulus and Study of Humidity Halos and Aerosol Indirect Radiative Effects", "author": [ { "family_name": "Lu", "given_name": "Miao-Ling", "clpid": "Lu-Miao-Ling" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The first part of the thesis focuses on understanding the characteristics of the cloud humidity halos, the significant enhancements in humidity around cumulus clouds, and their radiative impacts. The simulated cloud and halo properties were compared with the measurement data from the aircraft campaign \u2013 \"Cloud Halo\" conducted in Hawaii, 2001. The cloud halo spatial distribution, the relationship with the vertical wind shear, and the temporal variation with cloud lifetime are explored by the 3D numerical simulations. Results suggest that halos are formed as a result of evaporation of cloudy air or detrainment of high humidity by the turbulent mixing in the cloud lateral boundary regions, or simply due to cloud dissipation. Humidity halos absorb the incoming sunlight, warm the atmosphere, and cool the surface. The 3D radiative transfer model results show that the SW column absorption (surface - 3.4 km) enhanced by the halo is 1.32 W m-2 averaged over the cloud mature and dissipating stages, a 1.3% change in the absence of the halo, for the cloud of the Cloud Halo experiment.
\r\n\r\nThe second part of the thesis is to understand the first and second aerosol indirect effects by conducting 98 3D LES simulations of the marine stratocumulus clouds - under various conditions of nighttime and daytime, SST (sea surface temperature), aerosol number concentration, and large-scale subsidence rate. Based on the statistical analysis, the cloud optical depth is found to be positively correlated with the cloud liquid water path, which is mainly regulated by large-scale subsidence and SST. The regression analysis shows that the second aerosol indirect effect is more pronounced in clean than polluted clouds and that it increases (reduces) the cloud optical depth for the same relative change in aerosol number concentration than considering the Twomey (first indirect) effect alone. Introducing a small amount of giant sea salt aerosols into the simulation lowers the number of cloud droplets activated and initiates precipitation for non-drizzling clouds. It also results in a reduction of cloud optical depth by 3% - 77% for heavily drizzling cases.
", "doi": "10.7907/H3BE-W731", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:1593", "collection": "thesis", "collection_id": "1593", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05032005-180939", "primary_object_url": { "basename": "Title.pdf", "content": "final", "filesize": 185961, "license": "other", "mime_type": "application/pdf", "url": "/1593/15/Title.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Studies with the Aerosol Mass Spectrometer", "author": [ { "family_name": "Bahreini", "given_name": "Roya", "orcid": "0000-0001-8292-5338", "clpid": "Bahreini-Roya" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Beauchamp", "given_name": "Jesse L.", "orcid": "0000-0001-8839-4822", "clpid": "Beauchamp-J-L" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Fast time-response of the Aerodyne Aerosol Mass Spectrometer (AMS) makes it a well-suited instrument for ambient field measurements. On the other hand, laboratory chamber experiments provide the opportunity to study a specific system in a more controlled environment. The goal of this thesis is to provide a summary of laboratory and field measurements using the AMS.
\r\n\r\nDuring laboratory chamber photooxidation experiments of diiodomethane (CH2I2), particle nucleation was observed at CH2I2 concentrations down to 15 ppt, which is comparable to the total gas-phase iodine species measured at coastal areas. Iodine oxides and oxyacids were observed in the aerosol mass spectra obtained by the AMS, consistent with the known gas-phase chemistry.
\r\n\r\nAirborne measurements by the AMS during the ACE-Asia field study revealed that the non-refractory submicron aerosols in the pollution layers of the boundary layer up to 3700 m were mainly composed of sulfate, ammonium, and organics. These pollution plumes originated primarily from urban and industrial areas of China and Korea.
\r\n\r\nThe laboratory chamber experiments of oxidation of cycloalkenes, terpenes, and m-xylene provided the opportunity to study the Secondary Organic Aerosol (SOA) forming potential, i.e., yield, and determine SOA effective density and chemical composition. Evidence of acid-catalyzed heterogeneous chemistry in the ozonolysis of a-pinene was observed since the total AMS organic mass during the experiments with acidic seed particles had a greater contribution of higher molecular weight fragments. The mixtures of SOA compounds produced from similar precursors studied resulted in broadly similar AMS mass spectra. Thus, fragmentation patterns observed for biogenic vs. anthropogenic SOA can be potentially useful in determining the sources of ambient SOA.
", "doi": "10.7907/1YNP-QQ95", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:427", "collection": "thesis", "collection_id": "427", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02012005-131605", "primary_object_url": { "basename": "ChungThesis2.pdf", "content": "final", "filesize": 3579858, "license": "other", "mime_type": "application/pdf", "url": "/427/1/ChungThesis2.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Global Distribution, Radiative Forcing, and Climate Impact of Carbonaceous Aerosols", "author": [ { "family_name": "Chung", "given_name": "Serena Hsin-Yi", "orcid": "0000-0001-5030-5871", "clpid": "Chung-Serena-Hsin-Yi" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Schneider", "given_name": "Tapio", "clpid": "Schneider-T" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis is motivated by the need to better understand and quantify the climate effects of carbonaceous aerosols, i.e., black carbon (BC) and organic carbon (OC). Global three-dimensional distribution of carbonaceous aerosols is simulated online in a general circulation model (GCM). The carbonaceous aerosol model includes primary BC, primary OC, five groups of biogenic volatile organic compounds (BVOCs), and fourteen semi-volatile products of BVOC oxidation by O3, OH, and NO3, which condense to form secondary organic aerosols (SOAs) based on an equilibrium partitioning model. Human activities since the preindustrial period are predicted to have increased global burdens of BC and OC by an order of magnitude and almost tripled the SOA production rate. Based on an older emission inventory for BC, the direct radiative forcing of increased atmospheric BC burden is estimated to warm the atmosphere by 0.51 to 0.8 W m-2, depending on how BC is mixed with other tropospheric aerosols. For OC, the estimated anthropogenic direct radiative forcing at top of the atmosphere (TOA) is -0.1 to -0.2 W m-2, depending on the water-uptake property of OC. When BC, OC and sulfate are combined, the estimated direct radiative forcing at TOA is -0.39 to -0.78 W m-2. Using an updated emission inventory, direct radiative forcing of anthropogenic BC at TOA is estimated to be +0.33 and +0.6 W m-2, for BC mixed externally and internally with present-day level of sulfate, respectively. Using a GCM coupled to a mixed-layer ocean model, these estimated forcings for BC are predicted to warm surface air temperature by 0.2 to 0.37 K. The temperature increase is the largest over northern high latitutdes during winter and early spring. Even though the predicted global-averaged warming due to BC is less than that of greenhouse gases, significant regional differences do exist, such as substantial warming in central and eastern Russia predicted for BC. In addition to temperature increase, direct radiative forcing of anthropogenic BC is also predicted to lead to a change in the hydrological cycle by shifting the intertropical convergence zone northward.", "doi": "10.7907/d2ff-ad43", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:4546", "collection": "thesis", "collection_id": "4546", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11142003-134303", "primary_object_url": { "basename": "Thesis_Final.pdf", "content": "final", "filesize": 1659287, "license": "other", "mime_type": "application/pdf", "url": "/4546/1/Thesis_Final.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Understanding the Relationship between Aerosols and Clouds: Field Investigations and Instrument Development", "author": [ { "family_name": "VanReken", "given_name": "Timothy Mark", "orcid": "0000-0002-2645-4911", "clpid": "VanReken-Timothy-Mark" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Jonsson", "given_name": "Haflidi H.", "clpid": "Jonsson-H-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The research presented in this thesis is part of the ongoing effort to better understand the role of atmospheric aerosols in the development of clouds. Cloud condensation nuclei (CCN) are the subset of the aerosol population that can activate and grow into cloud droplets under suitable atmospheric conditions. The supersaturation at which a given CCN will activate is dependent on the particle's size and composition, but the details of the relationship are not completely understood. CCN observations from the CRYSTAL-FACE (Cirrus Regional Study of Tropical Anvils and Cirrus Layers- Florida Area Cirrus Experiment) field campaign are presented in Chapter 2. These measurements are compared to predictions based on measured aerosol size distributions with an assumed chemical composition to determine whether activation theory is sufficient to describe what is observed. The analysis indicates that, in cases like those included in the study, CCN concentrations can be accurately predicted from the size distribution even in the absence of detailed chemical compositional data.
\r\n\r\nA case study is described in Chapter 3 to demonstrate the potential importance of anthropogenic aerosols in the development of clouds. During a CRYSTAL-FACE flight, an aerosol plume was encountered in the boundary layer near the base of a large mixed-phase convective cloud. Evidence suggests that an oil-burning power plant south of Miami was the likely source of the plume. The convective cloud was probed at higher altitudes, and a spatial gradient was observed in the ice particle concentrations. The evidence linking the plume in the boundary layer to the upper-level trends is inconclusive, but worthy of further study.
\r\n\r\nThe measurement of CCN in the atmosphere is difficult, and improved instrumentation would significantly improve our ability to obtain the detailed information necessary to understand the relationship between aerosols and clouds. The concept for an improved CCN spectrometer is outlined in Chapter 4; this new design would expand the resolvable range of supersaturations for which data can be obtained. The dependence of the instrument's performance on various design parameters is evaluated, and a configuration is proposed that would be a significant improvement over currently available instrumentation.
", "doi": "10.7907/TGKK-QB38", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:2037", "collection": "thesis", "collection_id": "2037", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05252003-091827", "primary_object_url": { "basename": "Bhave_thesis.pdf", "content": "final", "filesize": 5717214, "license": "other", "mime_type": "application/pdf", "url": "/2037/1/Bhave_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Air Pollution at the Single-Particle Level: Integrating Atmospheric Measurements with Mathematical Models", "author": [ { "family_name": "Bhave", "given_name": "Prakash Viththal", "orcid": "0000-0002-2573-951X", "clpid": "Bhave-Prakash-Viththal" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Kleeman", "given_name": "Micheal J.", "clpid": "Kleeman-M-J" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Particulate air pollution is of growing concern in the United States and around the world. Elevated concentrations of aerosols (solid particles and liquid droplets suspended in air) are correlated with increased cases of lung cancer, cardiopulmonary disorders, and human mortality. A detailed understanding of the size, chemical composition, and concentration of atmospheric particles is needed to assess their effects on human health, as well as on regional visibility and global climate. One can acquire such knowledge through direct measurements, or by utilizing mathematical air quality models. New and innovative instruments allow us to measure the size and composition of individual particles, rather than to infer aerosol chemical properties from bulk particulate matter samples. Concurrently, air quality models have been developed to numerically simulate the emissions of discrete particles, and their transport and chemical evolution in the atmosphere. This thesis focuses on how to integrate and compare measurements taken by state-of-the-science single-particle instruments with the air pollutant properties calculated using state-of-the-science mathematical models. A 1996 field experiment conducted in the Los Angeles air basin serves as the case study for this thesis research.
\r\n\r\nComparisons of model calculations against single-particle observations identify specific areas where model improvements are needed, and also identify important areas for future instrumental development. These comparisons contribute to our understanding of atmospheric pollution at the single-particle level, and ultimately, may provide tremendous value to policy makers who are seeking least-cost solutions to urban and regional air quality problems. After presenting initial comparisons of single-particle measurements and model results, efforts to quantify and categorize the single-particle chemical composition data are described. The quantitatively reconstructed single-particle measurements are compared with mathematical model calculations of the atmospheric aerosol mixing characteristics. Finally, an example is presented of how the model and measurement combination enhance our ability to reduce particulate pollution in the air we breathe.
", "doi": "10.7907/ZA39-HJ32", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:2374", "collection": "thesis", "collection_id": "2374", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06022003-074653", "primary_object_url": { "basename": "Thesis08Jun03.pdf", "content": "final", "filesize": 4053288, "license": "other", "mime_type": "application/pdf", "url": "/2374/1/Thesis08Jun03.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Toward an Understanding of the Indirect Climatic Effect of Aerosols", "author": [ { "family_name": "Nenes", "given_name": "Athanasios", "orcid": "0000-0003-3873-9970", "clpid": "Nenes-Athanasios" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis is motivated by the need to improve our understanding of the aerosol indirect effect. The activation of aerosol into cloud droplets has been extensively studied, using a comprehensive numerical cloud droplet activation model. Using this model, the effect of water vapor mass transfer limitations on the cloud droplet activation process was first studied; it was found that mass transfer limitations are important for activation under polluted conditions. The potential effect of (currently unresolved) \"chemical effects\" on cloud droplet number (e.g., the presence soluble gases and surface active species) was also assessed. It was seen that small changes in aerosol and gas-phase composition can have a strong effect on cloud droplet number, and should be included in future estimates of the aerosol indirect effect.
\r\n\r\nA comprehensive aerosol activation parameterization was developed for use in a first-principle assessment of the aerosol indirect effect. This new parameterization introduces the concept of \"population splitting,\" in which the droplets are separated into two populations, each with its own growth characteristics. The effect of water vapor mass transfer limitations is explicitly introduced. The parameterization allows for treatment of chemical effects. The new parameterization shows excellent and robust agreement with a detailed numerical parcel model.
\r\n\r\nPreviously unidentified mechanisms of aerosol-cloud interactions were also explored. Aerosol, when it contains black carbon, can absorb light and heat the droplet enough to affect its activation behavior. This can affect cloud properties in numerous and counterintuitive ways; black carbon heating can dissipate clouds, but may also increase cloud lifetime (and lead to a climatic cooling) by decreasing the probability of drizzle formation.
\r\n\r\nFinally, the performance of instruments used for measuring the concentration of cloud condensation nuclei (CCN) was assessed. Each design exhibits different limitations and sources of uncertainty, but all show decreased ability to measure CCN of low critical supersaturation (<0.1%). The performance of the instrumentation can be very sensitive to the operating conditions. Therefore, an in-depth theoretical understanding of the instrumentation is necessary; otherwise, CCN measurements may be subject to considerable uncertainty.
", "doi": "10.7907/S02W-0573", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:2377", "collection": "thesis", "collection_id": "2377", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06022003-114148", "primary_object_url": { "basename": "thesis_kuang.pdf", "content": "final", "filesize": 5053381, "license": "other", "mime_type": "application/pdf", "url": "/2377/1/thesis_kuang.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "I: Remote Spectroscopic Measurements of Atmospheric HDO/H\u2082O and Column CO\u2082. II: Interannual Variations of the Earth\u2019s Reflectance", "author": [ { "family_name": "Kuang", "given_name": "Zhiming", "clpid": "Kuang-Zhiming" } ], "thesis_advisor": [ { "family_name": "Stevenson", "given_name": "David John", "clpid": "Stevenson-D-J" } ], "thesis_committee": [ { "family_name": "Stevenson", "given_name": "David John", "clpid": "Stevenson-D-J" }, { "family_name": "Ingersoll", "given_name": "Andrew P.", "clpid": "Ingersoll-A-P" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The theme of this thesis is to apply remote sensing data on problems concerning the climate system. It is grouped into two parts. Part I (Chapters 1, 2) is devoted to spectroscopic measurements of HDO, H\u2082O and column CO\u2082, and Part II (Chapters 3-5) is devoted to variations in the Earth's reflectance.
\r\n\r\nIn Chapter 1, we derive the first simultaneous measurements of HDO and H\u2082O in the tropical upper troposphere and lower stratosphere. This is made possible by extending the retrievals of the Atlas-3 Atmospheric Trace Molecule Spectroscopy (ATMOS) data deeper into the troposphere. The derived HDO/H\u2082O ratio demonstrates that convection has a major influence on the moisture budget and the dehydration processes in this region.
\r\n\r\nThe objective of Chapter 2 is to determine the precision to which column averaged CO\u2082 volume mixing ratio (VMR) can be measured by near-infrared (NIR) spectrometry of reflected sun light. The key idea in this study is the simultaneous use of the CO\u2082 (1.58-\u00b5m and 2.06-\u00b5m) and O\u2082 (0.76-\u00b5m) bands. This approach allows small changes in the spectrum arising from variations of column CO\u2082 VMR to be distinguished from those arising from variations of other atmospheric/surface parameters. Using prototype retrieval simulations based on a practical satellite instrument design, we show that the 3-band, high-resolution, spectrometric approach using NIR reflected sunlight has the potential for highly accurate column CO\u2082 VMR measurements.
\r\n\r\nIn Chapters 3-5, we examine the interannual variations in the Earth's reflectance. Chapter 3 introduces the Nimbus-7 TOMS reflectance measurements and provides an overview on the interannual variability of the Earth's reflectance. Variations in the globally averaged reflectance are also used to examine a postulated cosmic ray-cloud-climate connection.
\r\n\r\nIn Chapter 4, we relate interannual reflectance variations over the summertime polar icy areas to variations in the microwave-derived sea ice concentration. The results provide independent confirmation on sea ice variations observed by microwave instruments, and quantify the role of clouds in shielding the reflectance effect of sea ice variations. An interesting hemispheric asymmetry is found: a 1% change in the sea ice concentration is related to a significantly larger reflectance change in the Antarctic than in the Arctic icy areas.
\r\n\r\nChapter 5 is devoted to interannual reflectance variations over the northern midlatitude oceans. We find that interannual reflectance variations in these regions are, to a large extent, related to variations in the large scale circulation, mostly through variations in the storms tracks. The findings in this chapter suggest that the response of clouds to climate change may be better viewed from a large-scale circulation perspective, other than a purely thermodynamic one (such as in the cloud-temperature relations), a stand many previous investigations have taken.
", "doi": "10.7907/Q9TP-RR97", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:2526", "collection": "thesis", "collection_id": "2526", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06092005-132829", "primary_object_url": { "basename": "Wang_j_2003.pdf", "content": "final", "filesize": 11326648, "license": "other", "mime_type": "application/pdf", "url": "/2526/1/Wang_j_2003.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Instrument Development and Characterization of Atmospheric Aerosol Physical Properties Through Airborne Measurement", "author": [ { "family_name": "Wang", "given_name": "Jian", "clpid": "Wang-Jian" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" }, { "family_name": "Wennberg", "given_name": "Paul O.", "clpid": "Wennberg-P-O" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Atmospheric aerosol has significant impact on climate. It influences radiative transfer by scattering and absorbing sunlight and by changing the microphysical structure, lifetime, and amount of the clouds. Due to its short lifetime, the spatial and temporal distributions of tropospheric aerosol are highly inhomogeneous. Aircraft have proven to be an effective platform in characterizing the atmospheric aerosol. To maximize the potential and to reduce the artifacts associated with aircraft sampling, both improvements in existing instruments and developments of new instruments are required.
\r\n\r\nTo increase the speed of submicron aerosol size distribution measurements, a mixing condensation nucleus counter (MCNC) has been developed. By carefully designing the mixing chamber and condenser, the response time of the MCNC was significantly reduced. Our experiments demonstrate that a differential mobility analyzer (DMA) coupled with the developed MCNC can measure complete aerosol size distributions in as little as 2 seconds.
\r\n\r\nThe effects of bends and elbows on the diffusional losses of particle in nanometer range were studied. The results show that the effect of bends and elbows on particle diffusion loss is significant, and for Reynolds number smaller than 250, the enhancement of diffusion losses due to bends and elbows is sensitive to both the relative orientations of the bends and elbows and the lengths of straight tubing between them. Because of this sensitivity, direct calibration or simulation is required to assess nanoparticle penetration efficiencies for any flow system containing bends or elbows at low Reynolds number. When the Reynolds number exceeds 250, the enhancement is insensitive to the actual flow configurations. Experimental results are presented, which can be used for design of aerosol flow systems at Reynolds number larger than 250.
\r\n\r\nTo minimize the airborne sampling bias, an advanced differential mobility analyzer (DMA) system for measuring submicron aerosol size distribution at ambient relative humidity, with special attention to implementation on aircraft, has been developed. The system includes an active RH controller, a cylindrical differential mobility analyzer (CDMA), and a condensation nucleus counter. A cascade controller consisting of two PID modules maintains the RH inside the CDMA at ambient RH by actively adding or removing water vapor from the air stream. The flows are controlled with feedback PID controllers, which compensate for the variation of pressure as the aircraft changes altitude. This system was integrated into the CIRPAS Twin Otter aircraft and used to measure ambient size distributions during the Aerosol Characterization Experiment-Asia (ACE-Asia), carried out from March to May, 2001, in Japan.
\r\n\r\nDuring the ACE-Asia experiment, the above DMA system, together with an aerodynamic particle sizer (APS), was used to characterize aerosol size distributions in East Asia during 19 flights on board of CIRPAS Twin Otter aircraft. Besides providing the aerosol size characteristics, the data were combined with chemical composition and aerosol mixing state measurements to predict the vertical profile of aerosol extinction, which was compared with those derived from simultaneous direct measurements of aerosol optical depth by the NASA 14-channel sunphotometer. Agreement between the predicted and derived aerosol extinction varies for different scenarios, but the discrepancies were generally within the calculated uncertainties.
", "doi": "10.7907/GNFA-V973", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:6344", "collection": "thesis", "collection_id": "6344", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04212011-075629318", "primary_object_url": { "basename": "Sobrero_ac_2002.pdf", "content": "final", "filesize": 27921469, "license": "other", "mime_type": "application/pdf", "url": "/6344/1/Sobrero_ac_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Surface Structure Determination by Low-Energy Electron Diffraction", "author": [ { "family_name": "Sobrero", "given_name": "Aquiles Carlos", "clpid": "Sobrero-Aquiles-Carlos" } ], "thesis_advisor": [ { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" } ], "thesis_committee": [ { "family_name": "McKoy", "given_name": "Basil Vincent", "clpid": "McKoy-B-V" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Weinberg", "given_name": "William Henry", "clpid": "Weinberg-W-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Four aspects of low-energy electron diffraction (LEED) have been investigated: interpretation of spot patterns to determine the surface unit cell and possible ambiguities, development of a photographic method for measuring angles of incidence and determining alignment of the LEED instrument, study of reliability factors used for intensity analysis, and justification for equivalent beam averaging.
\r\n\r\nThe interpretation of LEED spot patterns to determine the geometry of the surface unit cell can be involved when there are several symmetrically equivalent structural domains contributing to the pattern. Complex patterns can be deciphered by the algorithm described in Chapter II. The algorithm determines a surface unit cell that is often unique but not always, as where a p(2 x 2) pattern from a fcc(111) surface can be produced by a true (2 x 2) overlayer or by three domains of a (2 x 1) structure. This ambiguity arises on surfaces with 6m symmetry, such as fcc(111) and hcp(0001), for spot patterns with threefold rotational symmetry.
\r\n\r\nIn Chapter III, a broadly applicable photographic method for measuring angles of incidence and determining the alignment of the LEED instruments is described. Two published methods for determining the angle of incidence are special cases of this general procedure. The procedure extends the photographic methods and facilitates the verification of the alignment of the components of the LEED instrument.
\r\n\r\nReliability factors are used to evaluate correspondence between computed and observed LEED intensity spectra. Zanazzi and Jona, Pendry, and Sobrero and Weinberg have proposed reliability factors that are examined in Chapter IV. Chapter V provides a theoretical analysis and shows that averaging over momentum space gives the best resolution of the surface structure while energy averaging smears out information in the intensity spectra.
\r\n\r\nChapter VI provides a theoretical basis for the procedure of equivalent beam averaging, which provides a first-order correction to LEED intensities for systematic error due to angular misalignment of the incident beam and corrects for misorientation (where the actual surface plane is at a slight angle to the desired crystal plane). The potential of higher-order corrections is discussed.
", "doi": "10.7907/9b54-km20", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6370", "collection": "thesis", "collection_id": "6370", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05032011-083245119", "primary_object_url": { "basename": "Liao_h_2002.pdf", "content": "final", "filesize": 9211227, "license": "other", "mime_type": "application/pdf", "url": "/6370/1/Liao_h_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Interactions between Tropospheric Chemistry and Aerosols in a Unified GCM Simulation", "author": [ { "family_name": "Liao", "given_name": "Hong", "clpid": "Liao-Hong" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Anthropogenic changes in the atmospheric abundances of tropospheric ozone and aerosols make significant contributions to climate change. In turn, climate change\r\naffects the abundances of ozone and aerosols, resulting in complicated feedbacks. To move toward understanding interactions and feedbacks among tropospheric chemistry,\r\naerosol formation, and climate change, a unified tropospheric chemistry-aerosol model is developed within the Goddard Institute for Space Studies general circulation model. The model includes a detailed simulation of tropospheric ozone-NO_x-hydrocarbon chemistry and a thermodynamic representation of sulfate/nitrate/ammonium aerosols. Two-way coupling between aerosols and chemistry provides consistent chemical fields for aerosol dynamics and aerosol mass for heterogeneous processes and calculations of gas-phase photolysis rates. Although the current version of the unified model does not include\r\nprognostic treatments of black carbon, organic carbon, and mineral dust aerosols, we include effects of these particles on photolysis and heterogeneous processes by using three-dimensional off-line fields. The unified model is applied to examine interactions between tropospheric chemistry and aerosols. This dissertation is the first step in the development of a fully-coupled climate/chemistry/aerosol model.\r\n", "doi": "10.7907/E2SZ-YX06", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6137", "collection": "thesis", "collection_id": "6137", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10122010-125450691", "type": "thesis", "title": "Representing Tropospheric Aerosols and Their Climatic Effects in Global Models", "author": [ { "family_name": "Adams", "given_name": "Peter Jonathan", "clpid": "Adams-Peter-Jonathan" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "In order to better understand and quantify the direct and indirect effect of aerosols on climate, an earlier general circulation model (GCM) simulation of tropospheric sulfate has been extended by incorporating aerosol thermodynamics and microphysics. The thermodynamic simulation allows the prediction of nitrate, ammonium, and aerosol water concentrations. It is estimated that nitrate contributes as much to total aerosol mass as sulfate on regional scales in parts of Europe and North America. The direct radiative forcing associated with the sulfate-nitrate-ammonium-water mixture is estimated to be \u20141.14 W M^(-2) for the present day. Based on a future emissions scenario, this could increase to as much as \u20142.13 W^(-2) by the year 2100, an increase that results from increased nitrate concentrations. Although currently a minor contributor to aerosol direct radiative forcing, nitrate is predicted to exceed sulfate in its contribution by the end of the century for this emissions scenario. It is also found that direct radiative forcing estimates are highly sensitive to aerosol behavior at relative humidity above 90%, highlighting the shortcomings of global models in their treatment of aerosol water uptake under partly cloudy conditions. The microphysical simulation allows the prediction of tropospheric aerosol number concentrations and size distributions, key parameters in determining the indirect effect of aerosols on clouds. A two-moment sectional algorithm is used to simulate the microphysical processes of condensation/evaporation and coagulation. It has been tested by performing a simulation of sulfate microphysics. Predicted aerosol number concentrations generally agree with observations to within 25%. The microphysical simulation also reproduces key features of the tropospheric aerosol such as increasing number concentrations with altitude and land-sea contrasts in cloud condensation nuclei concentrations. It is found that there are important uncertainties in the source rates of new particles to the atmosphere, whether from in situ nucleation or emissions of particulates, that can significantly impact predicted aerosol number and cloud condensation nuclei concentrations.", "doi": "10.7907/10CM-8W55", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6344", "collection": "thesis", "collection_id": "6344", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04212011-075629318", "primary_object_url": { "basename": "Sobrero_ac_2002.pdf", "content": "final", "filesize": 27921469, "license": "other", "mime_type": "application/pdf", "url": "/6344/1/Sobrero_ac_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Surface Structure Determination by Low-Energy Electron Diffraction", "author": [ { "family_name": "Sobrero", "given_name": "Aquiles Carlos", "clpid": "Sobrero-Aquiles-Carlos" } ], "thesis_advisor": [ { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" } ], "thesis_committee": [ { "family_name": "McKoy", "given_name": "Basil Vincent", "clpid": "McKoy-B-V" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Weinberg", "given_name": "William Henry", "clpid": "Weinberg-W-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Four aspects of low-energy electron diffraction (LEED) have been investigated: interpretation of spot patterns to determine the surface unit cell and possible ambiguities, development of a photographic method for measuring angles of incidence and determining alignment of the LEED instrument, study of reliability factors used for intensity analysis, and justification for equivalent beam averaging.
\r\n\r\nThe interpretation of LEED spot patterns to determine the geometry of the surface unit cell can be involved when there are several symmetrically equivalent structural domains contributing to the pattern. Complex patterns can be deciphered by the algorithm described in Chapter II. The algorithm determines a surface unit cell that is often unique but not always, as where a p(2 x 2) pattern from a fcc(111) surface can be produced by a true (2 x 2) overlayer or by three domains of a (2 x 1) structure. This ambiguity arises on surfaces with 6m symmetry, such as fcc(111) and hcp(0001), for spot patterns with threefold rotational symmetry.
\r\n\r\nIn Chapter III, a broadly applicable photographic method for measuring angles of incidence and determining the alignment of the LEED instruments is described. Two published methods for determining the angle of incidence are special cases of this general procedure. The procedure extends the photographic methods and facilitates the verification of the alignment of the components of the LEED instrument.
\r\n\r\nReliability factors are used to evaluate correspondence between computed and observed LEED intensity spectra. Zanazzi and Jona, Pendry, and Sobrero and Weinberg have proposed reliability factors that are examined in Chapter IV. Chapter V provides a theoretical analysis and shows that averaging over momentum space gives the best resolution of the surface structure while energy averaging smears out information in the intensity spectra.
\r\n\r\nChapter VI provides a theoretical basis for the procedure of equivalent beam averaging, which provides a first-order correction to LEED intensities for systematic error due to angular misalignment of the incident beam and corrects for misorientation (where the actual surface plane is at a slight angle to the desired crystal plane). The potential of higher-order corrections is discussed.
", "doi": "10.7907/9b54-km20", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6123", "collection": "thesis", "collection_id": "6123", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10112010-091412647", "primary_object_url": { "basename": "Fine_pm_2002.pdf", "content": "final", "filesize": 75776809, "license": "other", "mime_type": "application/pdf", "url": "/6123/1/Fine_pm_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "The Contribution of Biomass Combustion to Ambient Fine Particle Concentrations in the United States", "author": [ { "family_name": "Fine", "given_name": "Philip Malcolm", "clpid": "Fine-Philip-Malcolm" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Simoneit", "given_name": "Bernd R. T.", "clpid": "Simoneit-B-R-T" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Biomass combustion is an important source of fine particle emissions to the atmosphere. According to USEPA emissions inventories for the year 1995, approximately 20% of total primary PM_(2.5) emissions come from biomass combustion sources. As an alternative to inventory data such as this, source apportionment with chemical mass balance receptor models can determine the contribution of different fine particle source types to a particular ambient fine particle sample. The identification of individual organic compounds in the fine particle emissions from biomass combustion and other fine particle sources provides a rich source of potential molecular tracers that can be used in apportionment calculations.\r\n\r\nA series of experiments were conducted to characterize the fine particle emissions from the following biomass combustion sources: residential wood combustion in fireplaces, non-catalytic wood stoves, and catalytic wood stoves; the prescribed burning of foliar fuels; and the open burning of agricultural waste. Results include emission factors for particle mass, organic and elemental carbon, ionic species, selected elements, and over 200 individual organic compounds as determined by GC/MS analysis. The cellulose pyrolysis product, levoglucosan, was emitted from all of the biomass combustion sources and serves as a unique tracer for biomass combustion in general. Substituted syringols were emitted primarily from hardwood combustion, and resin acids were emitted exclusively from the burning of softwoods. Fine particle emission factors are lower and elemental carbon and PAH emissions are higher from wood stoves than from fireplaces. The burning of foliar fuels produces more alkanoic acids than wood combustion due to the higher concentration of plant waxes in the foliage.\r\n\r\nThe data from the residential wood combustion source tests were used in a chemical mass balance receptor model to determine the contribution of biomass combustion to ambient fine particle concentrations throughout the United States. Ambient samples collected as part of the IMPROVE and other sampling networks were combined into seasonal composite samples and analyzed for important molecular markers of biomass combustion and other fine particle sources. The resulting national map provides seasonal and geographical information on the significance of biomass combustion as a fine particle source in the United States.", "doi": "10.7907/B4VY-AS20", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6109", "collection": "thesis", "collection_id": "6109", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10062010-111511765", "primary_object_url": { "basename": "Pantu_p_2001.pdf", "content": "final", "filesize": 32331729, "license": "other", "mime_type": "application/pdf", "url": "/6109/1/Pantu_p_2001.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Methane Conversion to Synthesis Gas over Platinum Supported on Rare Earth Oxides", "author": [ { "family_name": "Pantu", "given_name": "Piboon", "clpid": "Pantu-Piboon" } ], "thesis_advisor": [ { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" } ], "thesis_committee": [ { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Davis", "given_name": "Mark E.", "orcid": "0000-0001-8294-1477", "clpid": "Davis-M-E" }, { "family_name": "Labinger", "given_name": "Jay A.", "orcid": "0000-0002-1942-9232", "clpid": "Labinger-J-A" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The central theme of this research is to study methane conversion to synthesis gas focusing on the redox capabilities of cerium oxide. Reaction of methane with platinum or ruthenium supported on Ce_(1-x)Zr_xO_2 (x=0, 0.2, 0.5) in the absence of gaseous oxygen was studied in a packed-bed reactor at 550-700\u00b0C. The oxidation of methane utilized lattice oxygen of the support, which was subsequently restored by reacting with oxygen in a separate step. Thus, by using theredox property of cerium oxide, methane oxidation can be carried out by air without diluting the product with nitrogen. Addition of ZrO_2 into CeO_2 increased the reducibility of the oxide as well as the rate of methane oxidation but decreased the selectivity to CO and H_2. The rate of oxidation was initially very fast but slowed down as the oxide support became progressively reduced. On the other hand, the selectivity increased with the reduction of the support and sharply rose to over 90% as the support attained 10%,40%, and 65% degree of reduction for the oxide compositions x=0, 0.2, and 0.5, respectively.
\r\n\r\nPartial oxidation of methane to synthesis gas over 0.5wt% Pt/Al_2O_3 and 0.5wt% PtfCeO_2 catalysts was studied in a packed-bed reactor. At temperatures up to 650\u00b0C, the PtfCeO_2 catalyst gave higher conversion and higher selectivity but the activity and selectivity became comparable to those of Pt/Al_2O_3 above 700\u00b0C. The Pt/CeO_2 catalyst also maintained high conversion and high selectivity when the CH_4:O_2 feed ratio varied from 1.7 to 2.3 while the Pt/Al_2O_3 catalyst had considerably lower selectivity under methane-rich conditions. The effect of reducibility of support on the catalytic activity was discussed. A multiple microreactor system for parallel testing of heterogeneous catalysts was developed. The reactor system was composed of nine tubular microreactors housed in a single wider tube and used a multiposition valve to conduct the reaction products sequentially from each microreactor to a mass spectrometer for analysis. The catalyst samples were prepared in the form of thin films coated on quartz rods for convenience of preparation and loading samples in the reactors. The system was tested with the reaction of methane reforming with carbon dioxide over Pt/Ce_(1-x)Gd_xO_(2-0.5x) and Pt/Ce_(1-x)Sm_xO_(2-0.5x) at 650\u00b0C and 700\u00b0C. The measurements showed that Pt/CeO_2 had the highest activity and, generally, the activity increased with cerium oxide content. After exposure to the feed stream for 2-3 hours at 700\u00b0C, most catalysts suffered significant deactivation with the exception of the mixed oxides with 25-85% samarium oxide that maintained relatively stable activity.
", "doi": "10.7907/rksa-xc11", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:1285", "collection": "thesis", "collection_id": "1285", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04072005-081230", "primary_object_url": { "basename": "Ostraat_ml_2001.pdf", "content": "final", "filesize": 11763159, "license": "other", "mime_type": "application/pdf", "url": "/1285/1/Ostraat_ml_2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Synthesis and Characterization of Aerosol Silicon Nanoparticle Nonvolatile Floating Gate Memory Devices", "author": [ { "family_name": "Ostraat", "given_name": "Michele Louisa", "orcid": "0000-0003-2678-6171", "clpid": "Ostraat-Michele-Louisa" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Silicon nanoparticle-based floating gate metal-oxide-semiconductor (MOS) field effect devices have potential for terabit cm-2 density nonvolatile memory applications. Aerosol synthesis of silicon nanoparticles is an important route toward the formation of discontinuous silicon nanoparticle floating gate structures that affords excellent control over particle size and size distribution, particle density, and oxide passivation. We have fabricated nanoparticle memory devices in a conventional MOS ultra-large scale integration (ULSI) process with channel lengths from 0.2 - 10 \u00b5m with a silicon nanoparticle floating gate fabricated by aerosol deposition.
\r\n\r\nSiO2 passivated silicon nanoparticles have been synthesized in an ultra clean two-stage aerosol reactor that is interfaced to a 200 mm wafer deposition chamber in a class 100 cleanroom. We synthesize silicon nanoparticles by thermal decomposition of silane gas at 950\u00b0C to produce single crystal, nonagglomerated nanoparticles. The second reactor stage passivated the silicon nanoparticles with a thin thermal oxide grown at 1050\u00b0C. Particles are thermophoretically deposited onto 200 mm silicon wafers with densities from 1013 particles cm-2 at the wafer center to 1011 particles cm-2 at the wafer edge in tens of minutes. We have fabricated floating gate memory devices in which the dielectric layer contains a discontinuous nanoparticle layer containing either (i) 2 -4 nm crystalline core diameter with 1 nm thermal oxide; or (ii) 6 - 15 nm crystalline core diameter with 2 nm thermal oxide. Cross-sectional transmission electron microscopy (TEM) verifies the presence of a silicon nanoparticle floating gate layer and planar TEM confirms nanoparticle morphology, size, and density.
\r\n\r\nAerosol floating gate devices exhibit normal transistor behavior and have promising nonvolatile device performance. Aerosol nanoparticle devices with 0.2 mm channel lengths exhibit threshold voltages < 5 V with large threshold voltage shifts (~ 2 V), submicrosecond program times and millisecond erase times. No degradation in program/erase threshold voltage swing was observed during 105 program and erase cycles, although some threshold voltage shift due to charge trapping was observed. Electrostatic modeling indicates when a discontinuous nanoparticle layer can be modeled as a continuous sheet charge embedded within oxide and when it should be modeled as individual nanoparticles in an array.
", "doi": "10.7907/FDGV-GS71", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:5123", "collection": "thesis", "collection_id": "5123", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12222006-125228", "primary_object_url": { "basename": "Griffin_RJ_2000.pdf", "content": "final", "filesize": 45759393, "license": "other", "mime_type": "application/pdf", "url": "/5123/1/Griffin_RJ_2000.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Experimental and computational studies of secondary organic aerosol formation", "author": [ { "family_name": "Griffin", "given_name": "Robert John", "clpid": "Griffin-R-J" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Dabdub", "given_name": "Donald", "clpid": "Dabdub-D" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Organic species are important constituents of tropospheric particulate matter in remote, rural, and urban areas. Such aerosol can be primary (emitted in the particle phase as solids or liquids) or secondary (formed in situ as condensable vapors) in nature. Secondary organic aerosol (SOA) is formed when products resulting from the gas-phase oxidation of a parent organic species partition to the particle phase. This partitioning can occur via condensation onto existing inorganic aerosol (heterogeneous-heteromolecular nucleation), absorption into an existing organic aerosol, dissolution to the aerosol aqueous phase, or homogeneous-heteromolecular nucleation.\n\nSOA yield is defined as the amount of SOA formed per the amount of a parent organic species that is oxidized. This yield depends functionally on stoichiometric and partitioning coefficients for each of the oxidation products formed and the total amount of organic aerosol mass available to act as absorptive media. Appropriate yield parameters are developed for a series of parent organics using smog chamber experiments. The effects of parent organic structure and the oxidizing species on SOA yield are also examined during the smog chamber experiments. Such yield parameters are used to model SOA formation from the oxidation of biogenic organic species on a global and annual scale. Yield parameters can also be used to define a new concept, the incremental aerosol reactivity for parent organic species, which is a convenient way of ranking parent organics in terms of their SOA-forming potentials.\n\nEfforts to improve the simulation of SOA formation in the California Institute of Technology three-dimensional air quality model are also described. The Caltech Atmospheric Chemistry Mechanism was designed to predict concentrations of the highly functionalized secondary organic oxidation products capable of leading to SOA. A module that treats formation of SOA thermodynamically is used to predict the distribution of these products between the gas- and aerosol-phases. The new mechanism and thermodynamic module will used to simulate a smog episode that occurred in 1993 in the South Coast Air Basin of California.", "doi": "10.7907/2F9Q-1772", "publication_date": "2000", "thesis_type": "phd", "thesis_year": "2000" }, { "id": "thesis:567", "collection": "thesis", "collection_id": "567", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02082008-164553", "type": "thesis", "title": "Experimental and theoretical studies of cloud condensation nuclei", "author": [ { "family_name": "Chuang", "given_name": "Patrick Yung-Shie", "clpid": "Chuang-Patrick-Yung-Shie" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Charlson", "given_name": "Robert", "clpid": "Charlson-R" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Cloud condensation nuclei (CCN), the subset of atmospheric aerosol that nucleate cloud droplet formation, are a key component in cloud formation, and are an important factor in controlling climatically-relevant cloud properties such as cloud albedo, cloud lifetime, and precipitation rate.
\r\n\r\nA CCN instrument that satisfies the constraints for small aircraft operation \u2014 minimum weight, volume, and power consumption, good robustness, and high frequency measurement \u2014 was constructed. The measurement technique was based on that of Hudson (1989) because it reportedly offered the ability to make measurements of CCN at all supersaturations simultaneously at high frequency and with good counting statistics. Modelling studies, and laboratory and field measurements, subsequently showed that this technique exhibits poor sensitivity. The CCN instrument was also studied in fixed supersaturation mode, where it is able to accurately measure CCN concentration at a fixed supersaturation, whose value ranges from 0.1 and 2%.
\r\n\r\nThe CCN instrument was flown during the 2nd Aerosol Characterization Experiment (ACE-2). The data were reported at a fixed supersaturation of 0.1%. Intercomparison of these measurements with those on two other aircraft shows good agreement. A sublinear relationship between measured CCN concentration and that predicted from aerosol size distribution and chemical composition measurements, Nmeas ~ N0.72pred. In-situ measurements of below-cloud CCN concentration and cloud droplet number concentration are compared. The results are in agreement with model predictions and with previous studies. Cloud droplet concentration is predicted to depend on the CCN spectrum and updraft velocity.
\r\n\r\nCloud droplet activation has often been assumed to be reasonably described by an equilibrium model. The error in calculated cloud droplet number concentration due to the influence of condensational growth kinetics was shown to be significant for some conditions. Such errors are estimated to lead to overestimates of indirect radiative climate forcing on the order of Wm-2. Accurate interpretation of measured CCN concentration may require consideration of activation kinetics associated with CCN instruments.
\r\n", "doi": "10.7907/RY6B-CY09", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:323", "collection": "thesis", "collection_id": "323", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01242008-085938", "primary_object_url": { "basename": "Kusaka_i_1998.pdf", "content": "final", "filesize": 6819732, "license": "other", "mime_type": "application/pdf", "url": "/323/1/Kusaka_i_1998.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Molecular Theory of Vapor Phase Nucleation", "author": [ { "family_name": "Kusaka", "given_name": "Isamu", "clpid": "Kusaka-Isamu" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "An attempt has been made to establish the foundation of molecular level theory of vapor phase nucleation. We have focused on evaluating the reversible work of cluster formation and followed two major trends in this direction, namely, statistical mechanical density functional theory and molecular level simulation.\r\n\r\nWe applied density functional theory to heterogeneous nucleation onto an ion. Our prime interest is to predict a sign preference of nucleation rate, which has been experimentally observed yet remained inexplicable in the classical framework. The theory indicates that asymmetry in ion-molecule interaction is directly responsible for the sign preference. The predicted sign dependence decreases as the supersaturation is increased. Our results from density functional theory agree well with the existing experimental observations.\r\n\r\nMolecular simulation offers an alternative to molecular level approach. A long-standing issue of fundamental importance in cluster simulation is the precise definition of a cluster. Thus far, all attempts of defining a cluster had introduced ad hoc criteria to determine unambiguously whether a given molecule in the system belongs to vapor or to a cluster for any instantaneous configuration of molecules. From a careful examination of the context in which a cluster should be introduced into nucleation theory, we conclude that such a criterion is unnecessary. Then, we present a new approach to cluster simulation which is free of any arbitrariness involved in the definition of a cluster. Instead, it preferentially and automatically generates the physical clusters, defined as the density fluctuations that lead to nucleation, and determines their equilibrium distribution in a single simulation. The latter feature permits one to completely bypass the computationally demanding free energy evaluation that is necessary in a conventional simulation. The method is applied first to water using the SPC/E model. We then turn to H2SO4/H2O binary system to obtain a large section of the reversible work surface. The resulting surface is markedly different from that in classical theory and indicates that the rate limiting step of stable particle formation in this system is the binary collision of the sulfuric acid hydrates.\r\n", "doi": "10.7907/jwwk-0n13", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:810", "collection": "thesis", "collection_id": "810", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02282008-110050", "primary_object_url": { "basename": "Schauer_jj_1998.pdf", "content": "final", "filesize": 19566989, "license": "other", "mime_type": "application/pdf", "url": "/810/1/Schauer_jj_1998.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Source contributions to atmospheric organic compound concentrations : emissions measurements and model predictions", "author": [ { "family_name": "Schauer", "given_name": "James Jay", "clpid": "Schauer-J-J" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Simoneit", "given_name": "Bernd R. T.", "clpid": "Simoneit-B-R-T" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nA dilution source sampling system is used to quantify the air pollutant emissions from major urban air pollution sources. The emissions from catalyst-equipped gasoline-powered motor vehicles, noncatalyst gasoline-powered motor vehicles, diesel trucks, meat charbroiling, the cooking of vegetables with seed oils, fireplace combustion of softwood and hardwood, cigarette combustion, and paint spray coating operations are characterized. Semi-volatile and particle-phase organic compounds in the diluted source emissions are collected simultaneously by both a traditional filter/PUF (polyurethane foam) sampling train and by an advanced organic compound-based denuder/filter/PUF sampling train to provide information on the gas/particle phase distribution of the semi-volatile organic compounds. Emission rates of hundreds of organic compounds, spanning carbon numbers from [...] to [...] are determined by gas chromatography/mass spectrometry and gas chromatography with flame ionization detection including n-alkanes, isoprenoids and other branched alkanes, cycloalkanes, aromatics, polycylic aromatic hydrocarbons, olefins, n-alkanoic acids, n-alkenoic acids, carbonyls, lactones, petroleum biomarkers, levoglucosan and other wood smoke markers, steroids, and synthetic chemicals. Fine particle mass emission rates and fine particle elemental chemical composition are measured as well.\r\n\r\nThe emissions profiles collected by use of the dilution source sampler are used to develop receptor-based air quality models that use organic compounds as tracers to determine source contributions to gas-phase and particle-phase air pollutant concentrations in the atmosphere. These models are applied to study source contributions to the existing particulate and gas-phase organic air pollution problems in Southern California and in California's San Joaquin Valley. In the Los Angeles area, diesel engine exhaust, fine particle paved road dust, food cooking operations and wood smoke are the largest contributors to annual average fine particle concentrations in the atmosphere, accompanied by smaller amounts of gasoline-powered vehicle exhaust aerosol, cigarette smoke, tire dust, plant fragments and natural gas combustion aerosol. In the San Joaquin Valley, wood smoke, background aerosol are found to be major contributors to the elevated fine particle concentrations experienced during the winter months.", "doi": "10.7907/3FPH-HY50", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:508", "collection": "thesis", "collection_id": "508", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02052008-131756", "primary_object_url": { "basename": "Winner_da_1998.pdf", "content": "final", "filesize": 20671619, "license": "other", "mime_type": "application/pdf", "url": "/508/1/Winner_da_1998.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Long-term modeling of regional ozone concentrations and control strategies", "author": [ { "family_name": "Winner", "given_name": "Darrell Alan", "clpid": "Winner-D-A" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The capability to accurately model the long-term frequency of occurrence of high and low ozone concentrations in the urban and regional atmosphere is developed. A full year of hourly ozone concentration predictions is generated throughout Southern California using a photochemical airshed model driven by automated assimilation of routine meteorological observations. Statistical measures of airshed model performance for the full year are comparable to results achieved by episodic models for 2-3 days of simulation that are driven by data from expensive special field measurement programs.
\r\n\r\nThe effect of alternative emission control strategies on the long-term frequency distribution of daily peak ozone concentrations in Southern California is determined. Ozone isopleth diagrams are constructed in terms of the number of days per year that the current U.S. Federal 8 h average and former 1 h average ozone standards will be exceeded at all feasible combinations of air basin-wide reactive organic gases and oxides of nitrogen emissions. It is found that the frequency of violation of the former 1 h average ozone standard set at 0.12 ppm ozone could be reduced to approximately 25 days per year through stringent emissions controls under 1987 meteorological conditions. No practical way is evident to even come close to meeting the new 8 h average standard set at 0.08 ppm ozone. It is shown that the days with the highest historically observed ozone concentrations are not necessarily the hardest days to bring below the air quality standard.
\r\n\r\nUse of synthetic meteorological data is explored as an efficient means to meet the input data requirements of airshed models that must operate over long periods of tine. A semi-Markov process is used to generate a time series of synoptic weather conditions that statistically resembles the occurrence and persistence of historically observed weather. Local weather variables then are drawn for each day that are representative of the meteorological potential for ozone formation. These values are used as the initial conditions for a prognostic mesoscale meteorological model that generates the meteorological fields needed by a photochemical airshed model. The procedure produces daily peak 8 h average ozone concentration predictions that compare well with historical observations.
\r\n", "doi": "10.7907/WAJM-9058", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:201", "collection": "thesis", "collection_id": "201", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01162008-085509", "primary_object_url": { "basename": "Meng_z_1997.pdf", "content": "final", "filesize": 12820627, "license": "other", "mime_type": "application/pdf", "url": "/201/1/Meng_z_1997.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Thermodynamic and dynamic modeling of atmospheric aerosols", "author": [ { "family_name": "Meng", "given_name": "Zhaoyue", "clpid": "Meng-Z" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Yung", "given_name": "Yuk L.", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThis dissertation investigates thermodynamic and dynamic modeling of urban and regional atmospheric aerosols. A rigorous and efficient aerosol thermodynamic model, SCAPE2, is developed. The model considers the inorganic aerosol system of sulfate, nitrate, ammonium, chloride, sodium, potassium, calcium, magnesium, carbonate, and water. SCAPE2 can be used to predict either the equilibrium gas/aerosol partition of volatile inorganic species or the particle surface vapor concentrations if applied to the aerosol phase only. It has also the option of predicting the equilibrium or metastable aerosol water content.\r\n\r\nA three-dimensional, size- and chemically-resolved aerosol dynamic model is developed by incorporating the aerosol thermodynamic model, SCAPE2, into an urban airshed model (CIT model). The model includes advection, turbulent diffusion, condensation/evaporation, nucleation, emissions, and dry deposition. Gas-to-particle conversion is represented by dynamic mass transfer between the gas and aerosol phases. The model employs an absorption approach in dynamically modeling production of secondary organic aerosols. A calculation method for dry deposition of aerosol particles is proposed.\r\n\r\nThe aerosol model is applied to simulate gas and aerosol behavior in the 27-29 August episode in the 1987 Southern California Air Quality Study (SCAQS). Simulation results are compared systematically against SCAQS measurements, and general good agreement is observed. The assumption that volatile inorganic species such as [...] are at instantaneous, local equilibrium is examined and it is found that, in many instances, gas/aerosol mass transfer limits the rate of gas-to-particle conversion.\r\n", "doi": "10.7907/0jjb-5n70", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:4987", "collection": "thesis", "collection_id": "4987", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12132007-083330", "primary_object_url": { "basename": "Dabdub_d_1996.pdf", "content": "final", "filesize": 22329563, "license": "other", "mime_type": "application/pdf", "url": "/4987/1/Dabdub_d_1996.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Mathematical modeling of air pollution dynamics by parallel computation", "author": [ { "family_name": "Dabdub", "given_name": "Donald", "clpid": "Dabdub-D" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Van de Velde", "given_name": "Eric", "clpid": "van-de-Velde-E" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Keller", "given_name": "Herbert Bishop", "clpid": "Keller-H-B" }, { "family_name": "Chandy", "given_name": "K. Mani", "clpid": "Chandy-K-M" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The use of massively parallel computers provides an avenue to overcome the computational requirements in the study of atmospheric chemical dynamics. General considerations on parallel implementation of air quality models are outlined including domain decomposition strategies, algorithm evaluation and design, portability, modularity, and buffering techniques used in I/O operations. Results are given for the implementation of the CIT urban air pollution model on distributed memory multiple instruction / multiple data (MIMD) machines ranging from a cluster of workstations to a 512 node Intel Paragon.\r\n\r\nThe central challenge in developing a parallel air pollution model is the implementation of the chemistry and transport operators used in the solution of the atmospheric reaction-diffusion equation. The chemistry operator is generally the most computationally intensive step in atmospheric air quality models. A new method based on Richardson extrapolation to solve the chemical kinetics is presented. The transport operator is the most challenging to solve numerically. Because of its hyperbolic nature non-physical oscillations and/or negative concentrations appear near steep gradient regions of the solution. Six algorithms for solving the advection equation are compared to determine their suitability for use in parallel photochemical air quality models. Four algorithms for filtering the numerical noise produced when solving the advection equation are also compared.\r\n\r\nA speed-up factor of 94.9 has been measured when the I/O, transport, and chemistry portions of the model are performed in parallel. This work provides the computational infrastructure required to incorporate new physico-chemical phenomena in the next generation of urban- or regional-scale air quality models.\r\n\r\nFinally, the SARMAP model is used to model the San Joaquin Valley of California. SARMAP is the updated version of RADM. It can be considered a state-of-the- art regional air pollution model. Like the CIT model, SARMAP incorporates the following atmospheric phenomena: gas-phase chemistry, advection and diffusion. In addition, SARMAP incorporates aqueous-phase chemistry and transport through cumulus clouds. Sensitivity studies performed show a significant dependence of ozone model predictions on boundary conditions.", "doi": "10.7907/k1ap-np35", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:5091", "collection": "thesis", "collection_id": "5091", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12202007-134328", "primary_object_url": { "basename": "Russell_lm_1996.pdf", "content": "final", "filesize": 25924668, "license": "other", "mime_type": "application/pdf", "url": "/5091/1/Russell_lm_1996.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "The physics and chemistry of marine aerosols", "author": [ { "family_name": "Russell", "given_name": "Lynn M.", "orcid": "0000-0002-6108-2375", "clpid": "Russell-L-M" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Understanding the physics and chemistry of the marine atmosphere requires both predicting the evolution of its gas and aerosol phases and making observations that reflect the processes in that evolution. This work presents a model of the most fundamental physical and chemical processes important in the marine atmosphere, and discusses the current uncertainties in our theoretical understanding of those processes. Backing up these predictions with observations requires improved instrumentation for field measurements of aerosol. One important advance in this instrumentation is described for accelerating the speed of size distribution measurements. Observations of aerosols in the marine boundary layer during the Atlantic Stratocumulus Transition Experiment (ASTEX) provide an illustration of the impact of cloud processing in marine stratus. More advanced measurements aboard aircraft were enabled by redesigning the design of the system for separating particles by differential mobility and counting them by condensational growth. With this instrumentation, observations made during the Monterey Area Ship Tracks (MAST) Experiment have illustrated the role of aerosol emissions of ships in forming tracks in clouds. High-resolution gas chromatography and mass spectrometry was used with samples extracted by supercritical fluid extraction in order to identify the role of combustion organics in forming ship tracks. The results illustrate the need both for more sophisticated models incorporating organic species in cloud activation and for more extensive boundary layer observations.\r\n", "doi": "10.7907/ZRQC-R241", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:3256", "collection": "thesis", "collection_id": "3256", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08282007-080127", "primary_object_url": { "basename": "Harley_ra_1993.pdf", "content": "final", "filesize": 35697243, "license": "other", "mime_type": "application/pdf", "url": "/3256/1/Harley_ra_1993.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Mathematical Modeling of Gas-Phase Organic Air Pollutants", "author": [ { "family_name": "Harley", "given_name": "Robert Adam", "clpid": "Harley-Robert-Adam" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Volatile organic compounds (VOCs) play a significant role in the production of ozone in urban atmospheres. In addition, VOCs are of concern because some of them are toxic, and because the atmospheric oxidation of directly emitted VOCs can form condensable products which contribute to airborne particulate matter concentrations. In this study, a general model that relates pollutant emissions to ambient VOC concentrations is described. Model performance is evaluated both for ozone and VOCs for the August 27-29, 1987 period in the Los Angeles area using data from the Southern California Air Quality Study (SCAQS).\r\n\r\nImproved chemical composition profiles for major VOC emission sources are presented, and use of these profiles results in significant changes to previous emissions estimates for many individual VCs. Reconciliation of emission data with speciated ambient VOC concentration data from the Los Angeles area indicates that there is much more unburned gasoline in the atmosphere than the emission inventory suggests.\r\n\r\nThree photochemical airshed models are presented that predict the ambient concentrations of VOCs. The first model predicts concentrations of lumped VOC classes (e.g. lumped canes, monoalkyl benzenes). Satisfactory model performance is obtained only after the VOC emission estimates prepared by the government are scaled up to match emission rates measured in the Van Nuys tunnel. An enhanced airshed model with 53 individual VOCs represented explicitly also is described and tested. The best performance is obtained for aromatic hydrocarbons which are predicted to within \u00b120% by the model in most cases; concentrations of most other species are predicted to better than \u00b150%. Finally, a model for gas-phase toxic organic air pollutants is described and tested for species including aromatics, aldehydes, ketones, and 1,3-butadiene among others. Significant contributions to total ambient concentrations from atmospheric photochemical formation are found for formaldehyde, acetaldehyde, propionaldehyde, acrolein and methyl ethyl ketone. Therefore, control programs for some toxic air pollutants must consider photochemical formation pathways in addition to direct emissions.\r\n\r\nThe novel aspects of this study include the analysis and improvement of speciated VOC emission estimates, and the development and testing of airs hed models for lumped and individual VOCs using data from SCAQS.", "doi": "10.7907/va0x-2331", "publication_date": "1993", "thesis_type": "phd", "thesis_year": "1993" }, { "id": "thesis:3256", "collection": "thesis", "collection_id": "3256", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08282007-080127", "primary_object_url": { "basename": "Harley_ra_1993.pdf", "content": "final", "filesize": 35697243, "license": "other", "mime_type": "application/pdf", "url": "/3256/1/Harley_ra_1993.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Mathematical Modeling of Gas-Phase Organic Air Pollutants", "author": [ { "family_name": "Harley", "given_name": "Robert Adam", "clpid": "Harley-Robert-Adam" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Volatile organic compounds (VOCs) play a significant role in the production of ozone in urban atmospheres. In addition, VOCs are of concern because some of them are toxic, and because the atmospheric oxidation of directly emitted VOCs can form condensable products which contribute to airborne particulate matter concentrations. In this study, a general model that relates pollutant emissions to ambient VOC concentrations is described. Model performance is evaluated both for ozone and VOCs for the August 27-29, 1987 period in the Los Angeles area using data from the Southern California Air Quality Study (SCAQS).\r\n\r\nImproved chemical composition profiles for major VOC emission sources are presented, and use of these profiles results in significant changes to previous emissions estimates for many individual VCs. Reconciliation of emission data with speciated ambient VOC concentration data from the Los Angeles area indicates that there is much more unburned gasoline in the atmosphere than the emission inventory suggests.\r\n\r\nThree photochemical airshed models are presented that predict the ambient concentrations of VOCs. The first model predicts concentrations of lumped VOC classes (e.g. lumped canes, monoalkyl benzenes). Satisfactory model performance is obtained only after the VOC emission estimates prepared by the government are scaled up to match emission rates measured in the Van Nuys tunnel. An enhanced airshed model with 53 individual VOCs represented explicitly also is described and tested. The best performance is obtained for aromatic hydrocarbons which are predicted to within \u00b120% by the model in most cases; concentrations of most other species are predicted to better than \u00b150%. Finally, a model for gas-phase toxic organic air pollutants is described and tested for species including aromatics, aldehydes, ketones, and 1,3-butadiene among others. Significant contributions to total ambient concentrations from atmospheric photochemical formation are found for formaldehyde, acetaldehyde, propionaldehyde, acrolein and methyl ethyl ketone. Therefore, control programs for some toxic air pollutants must consider photochemical formation pathways in addition to direct emissions.\r\n\r\nThe novel aspects of this study include the analysis and improvement of speciated VOC emission estimates, and the development and testing of airs hed models for lumped and individual VOCs using data from SCAQS.", "doi": "10.7907/va0x-2331", "publication_date": "1993", "thesis_type": "phd", "thesis_year": "1993" }, { "id": "thesis:3029", "collection": "thesis", "collection_id": "3029", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08062007-150332", "primary_object_url": { "basename": "Kim_yp_1992.pdf", "content": "final", "filesize": 8931579, "license": "other", "mime_type": "application/pdf", "url": "/3029/1/Kim_yp_1992.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Simulation of multicomponent aerosol dynamics", "author": [ { "family_name": "Kim", "given_name": "Yong Pyo", "clpid": "Kim-Y-P" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Okuyama", "given_name": "Kikuo", "clpid": "Okuyama-K" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Chemical composition and, therefore, several physical properties, such as refractive index or density, of an aerosol system may be distributed in one particle size. The effect of these particles of the same size but different properties, so-called mixed particles, on aerosol dynamics can be important. Several aspects of the number-property distribution; effect on aerosol dynamics and importance, definition, state of the art of the measurement technique, available data, and numerical schemes are discussed and further research directions are discussed.\r\n\r\nThe moving sectional method is extended to simulate multicomponent aerosol dynamics resulting from condensation/evaporation processes. This method uses a Lagrangian approach in which section boundaries and component masses in a section vary according to the characteristics of condensation/evaporation rates while conserving number concentration in a section throughout the simulation. Simulation of model problems for which new analytical solutions have been obtained shows excellent agreement with the analytical solutions. Limitations and applicability of the sectional method are discussed.\r\n\r\nA technique for direct numerical solution of the multicomponent aerosol general dynamic equation is developed and tested. The method obtains the aerosol size-composition distribution without the need to make any a priori assumptions about the nature of the distribution. Numerical solutions are compared with analytical solutions for model problems of pure condensation/evaporation, pure coagulation, and simultaneous condensation and coagulation. The advantages, applicability, and the limitations of the approach are discussed.\r\n\r\nAn analysis of the tandem differential mobility analyzer (TDMA) is proposed in which the conditioner between the two DMAs is simulated by the multicomponent aerosol general dynamic equation (GDE). The use of the TDMA to separate an externally mixed aerosol is illustrated by simulating the data of Liu et al. (1978).\r\n\r\nNumerical issues in grid-based photochemical air quality models are reviewed. Numerical schemes for advection and chemical kinetics in gas-phase and for dynamics in aerosol-phase are compared.\r\n\r\nFinally, a numerical code is developed based on direct numerical solution of the multicomponent aerosol general dynamic equation.", "doi": "10.7907/SE1X-K706", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "id": "thesis:3159", "collection": "thesis", "collection_id": "3159", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08172007-132240", "primary_object_url": { "basename": "Wyslouzil_be_1992.pdf", "content": "final", "filesize": 42353894, "license": "other", "mime_type": "application/pdf", "url": "/3159/1/Wyslouzil_be_1992.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Aspects of homogeneous nucleation", "author": [ { "family_name": "Wyslouzil", "given_name": "Barbara Ellen", "clpid": "Wyslouzil-B-E" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Okuyama", "given_name": "Kikuo", "clpid": "Okuyama-K" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nExperimental investigations of vapor phase binary nucleation were carried out for both the methanesulfonic acid-water and the sulfuric acid-water systems. A rapid mixing device produced acid-water aerosols under isothermal conditions and at relative acidities (Ra), 0.04 < Ra < 0.65, relative humidities (Rh), 0.01 < Rh < 0.65, and temperatures, T = 20, 25 and 30\u00b0C. The number concentration of the aerosol at the exit of the nucleation and growth tube is extremely sensitive to the binary nucleation rate. Thus at low particle concentrations, when condensation did not significantly change the saturation levels the binary nucleation rates were estimated from the number concentration data as a function of Ra, Rh and temperature. Particle size distributions were also measured and found to vary with the amount of acid and water present. An integral model considering both nucleation and growth simulated the experimental system and predicted the total number of particles, the total mass in the aerosol phase, and the mass average diameter at the exit of the nucleation and growth tube. The simulations reproduced the experimental results quite well for the methansulfonic acid-water binary, if the nucleation rate was adjusted by a temperature dependent correction factor which ranged from [...] to [...]. Further analysis showed that the ratio of experimental to theoretical nucleation rates for both acid-water systems was a strong function of the predicted number of acid molecules in the critical nucleus.\r\n\r\nClassical homogeneous nucleation theory was extended to nonisothermal conditions by simultaneously solving cluster mass and energy balances. In vapor phase nucleation, the steady state nucleation rate was lower than the corresponding isothermal rate and this discrepancy increased as the pressure of the background gas decreased. After the initial temperature transients decayed, subcritical clusters were found to have temperatures elevated with respect to that of the background gas.", "doi": "10.7907/5M1F-WC03", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "id": "thesis:4589", "collection": "thesis", "collection_id": "4589", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11162005-134952", "primary_object_url": { "basename": "Lee_jh_1991.pdf", "content": "final", "filesize": 10473539, "license": "other", "mime_type": "application/pdf", "url": "/4589/1/Lee_jh_1991.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Robust Inferential Control: A Methodology for Control Structure Selection and Inferential Control System Design in the Presence of Model/Plant Mismatch", "author": [ { "family_name": "Lee", "given_name": "Jay Hyung", "clpid": "Lee-Jay-Hyung" } ], "thesis_advisor": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" } ], "thesis_committee": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Sideris", "given_name": "Athanasios", "clpid": "Sideris-A" }, { "family_name": "Doyle", "given_name": "John Comstock", "clpid": "Doyle-J-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Two major tasks that are required to obtain a control system utilizing secondary measurements are measurement selection and inferential control system design. The first involves choosing an appropriate subset of the available measurements and the second involves designing a feedback controller based on the chosen measurements. The important issues to be addressed are not only the theoretical performance of the closed-loop system, but also the effects arising from the factors prevalent in practical environments such as model/plant mismatch, constraints, and failures of actuators and sensors.
\r\n\r\nGeneral measurement selection methodology is developed accounting for all the factors that can affect the measurement selection in signifcant ways. These factors include model uncertainty, signal-to-noise ratios, and measurement dynamics. The underlying philosophy is to reduce the number of candidates to a sufficiently low level before going onto detailed analysis by eliminating those candidates for which there does not exist a linear time-invariant controller meeting the required level of robust performance. Based on this philosophy and using the Structured Singular Value theory as a vehicle, a number of numerically efficient screening tools are developed. Conditions are derived under which some of the new criteria reduce to previously published measurement selection criteria. The proposed tools are applied to the measurement selection problems in a multi-component distillation column and a high-purity distillation column.
\r\n\r\nTwo different approaches are considered for inferential control system design: an output estimation based design approach and a state estimation based design approach. The former approach involves independent design of an output estimator and a feedback controller while the latter involves direct one step design although the design can be actually separated into those of a state estimator and of a feedback regulator using the separation principle argument.
\r\n\r\nFor the former approach, design of the output estimator was examined for two different cases: the case where a full dynamic model is available and the case where only the time records of the primary and secondary measurements are available either from simulations or from process measurements. For the former case, multi-rate Kalman filter design and \u03bc-Synthesis design are discussed. For the latter case, the estimator design problem is formulated as a regression problem and various regression techniques are evaluated in terms of their suitability to the output estimator design problem. For design of the feedback controller, traditional techniques such as LQG, IMC, and MPC were combined into a control technique that has nice algorithmic properties as well as many operational merits such as straightforward constraint handling and simple, intuitive on-line tuning. A heavy-oil fractionator was used as an example application.
\r\n\r\nFor the latter approach, general state estimation techniques (e.g., multi-rate Kalman filtering) used in LQG and finite receding horizon control used in traditional MPC were integrated into a control technique that can incorporate general disturbances and multi-rate sampled measurements and has desirable operational characteristics. The concept of classical IMC was extended to equip the control system with on-line tuning parameters that have direct connections with the speed of the closed-loop responses. Application to a high purity distillation column demonstrates the effectiveness of the control technique in terms of closed-loop performance and operational flexibility.
", "doi": "10.7907/3dp3-ba80", "publication_date": "1991", "thesis_type": "phd", "thesis_year": "1991" }, { "id": "thesis:1649", "collection": "thesis", "collection_id": "1649", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05062004-154106", "primary_object_url": { "basename": "Pandis_sn_1991.pdf", "content": "final", "filesize": 12221876, "license": "other", "mime_type": "application/pdf", "url": "/1649/1/Pandis_sn_1991.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Studies of physicochemical processes in atmospheric particles and acid deposition", "author": [ { "family_name": "Pandis", "given_name": "Spyros N.", "orcid": "0000-0001-8085-9795", "clpid": "Pandis-S-N" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nAtmospheric particles, or particulate matter, can be solid or liquid with diameters varying from around 0.002[micrometers] to roughly 100[micrometers]. Atmospheric aerosol sources can be classified as primary or secondary, with the primary aerosol being directly emitted from the corresponding sources and the secondary particles being formed in the atmosphere, for example, from gas-phase chemical reactions that produce condensable vapors. At the same time aerosol particles are ultimately connected with the formation of water droplets and equivalently with the formation of clouds and fogs in the atmosphere.\r\n\r\nThe first part of this thesis concerns the mathematical modeling of wet and dry acid deposition and of the relevant physicochemical processes. Acid deposition consists of the delivery of acidic substances, principally sulfuric and nitric acid, from the atmosphere to the earth's surface. Upon emission to the atmosphere, SO2 and NOx, are photochemically oxidized, yielding sulfuric and nitric acid vapors. Sulfuric acid is rapidly incorporated into aerosol particles, while nitric acid may be scavenged by particles or droplets or remain in the gas phase. Even in the absence of an aqueous phase (no clouds or fog), the acidic gases and dry particles can be transported to and deposited at ground level; this process is called dry deposition. When an aqueous phase is present (inside a cloud or a fog), gas-phase species like SO2, HNO3, NH3 and aerosol particles are scavenged by water droplets resulting in a solution that can be significantly acidic. Additional cloudwater or fogwater acidity beyond that attained purely from scavenging of gases and particles results from aqueous-phase chemistry, most notably oxidation of dissolved SO2 to sulfuric acid. These acidic droplets can reach the earth's surface either as precipitation or as impacted cloud and fogwater, in the processes termed wet deposition. If they are not rained or deposited out the aqueous droplets can evaporate leaving as residue new aerosol particles that may themselves undergo dry deposition to the earth's surface. The effects of acid deposition include soil and lake acidification, forest decline and deterioration of cultural monuments.\r\n\r\nMathematical models are a major tool in our effort to understand and ultimately control acid deposition. The development of such a mathematical model represents a major challenge as it requires the ability to describe the entire range of atmospheric physicochemical phenomena.\r\n\r\nAs a first step in the modeling, a comprehensive chemical mechanism for aqueous-phase atmospheric chemistry was developed and its detailed sensitivity analysis was performed. The main aqueous-phase reaction pathways for the system are the oxidation of S(IV) to S(VI) by H2O2, OH, HO2, O2 (catalysed by Fe3+ and Mn2+), O3, and [...]. The dominant pathway for HNO3(aq) acidity is scavenging of nitric acid from the gas phase. HCOOH is produced because of the reaction of HCHO(aq) with OH(aq). The gas-phase concentrations of SO2, H2O2, HO2, OH, O3, HCHO, NH3, HNO3, and HCl are of primary importance. Increase of the liquid water content of the cloud results in a decrease of the sulfate concentration, but an increase of the total sulfate amount in the aqueous-phase. On the basis of the sensitivity analysis, a condensed mechanism was derived.\r\n\r\nThe next step was the development of a model that actually predicts the amount of liquid water in the atmosphere solving the energy balance. This Lagrangian model combines for the first time a detailed description of gas and aqueous-phase atmospheric chemistry with a treatment of the dynamics of radiation fog, that is the fog that is created due to the radiative cooling of the earth's surface to the space during the night. The model was evaluated against a well documented radiation fog episode in Bakersfield in the San Joaquin Valley of California over the period January 4-5, 1985. This application showed that the model predictions for temperature profile, fog development, liquid water content, gas-phase concentrations of SO2, HNO3, and NH3, pH, aqueous-phase concentrations of [...], [...], and [...], and finally deposition rates of the above ions match well the observed values. The fog was found to lead to a drastic increase of deposition rates over those in its absence for the major ionic species, with most notable being the increase of sulfate deposition. Several important differences were found to exist between the characteristics of a radiation fog and a representative cloud environment. Radiation fogs typically develop under stable conditions (very low wind speed) resulting in weak mixing and significant vertical gaseous species concentration gradients. Because of the proximity of the fog to ground-level sources of pollutants like SO2 and NOx, the corresponding gas-phase concentrations can reach much higher levels that in a cloud. In such a case, pathways for aqueous-phase sulfate production that are of secondary importance in a cloud environment may become significant in a fog.\r\n\r\nThe next level of treatment beyond assuming that all the water droplets have the size and chemical composition is to explicitly model the size-composition distribution of droplets as a result of nucleation on aerosol particles. A third model was developed to study the distribution of acidity and solute concentration among the various droplet sizes in a fog or a cloud. The major finding of this study was that significant solute concentration differences can occur in aqueous droplets inside a fog or a cloud. For the fog simulated, during the period of dense fog, the solute concentration in droplets larger than 10[micrometers] diameter increased with size, in such a way that droplets of diameter 20[micrometers] attain a solute concentration that is a factor of 3.6 larger than that in the 10[micrometer] droplets. Chemical processes tend to decrease the total solute mass concentration differences among the various droplet sizes. Low cooling rates of the system also tend to decrease these concentration differences while high cooling rates have exactly the opposite effect. The mass/size distribution of the condensation nuclei influences quantitatively, but not qualitatively, the above concentration differences.\r\n\r\nThe effects of equilibration processes on wet and dry deposition were then investigated and furthermore the accuracy of the currently used modelling approaches of these phenomena was examined. Atmospheric equilibration processes between two phases with different deposition velocities have the potential to affect significantly the amount of total material deposited on the ground. The magnitude of the effects of the equilibration processes depends primarily on the ratio of the deposition velocities of the two phases, on the production/emission rate of the gas-phase species, and on the initial distribution of species between the two phases.\r\n\r\nAt this point all the tools were available for the detailed investigation of the cyclical relationship between the aerosol and aqueous droplets; a polluted atmosphere with high aerosol concentration assists the formation of the aqueous phase which itself appears to enhance smog production, visibility reduction and aerosol sulfate levels after its dissipation. A model including descriptions of aerosol and droplet microphysics, gas and aqueous-phase chemistry and deposition was used to study the transformation of aerosol to fog droplets and back to aerosol in an urban environment. Fogs in polluted environments have the potential to increase aerosol sulfate concentrations, but at the same time to cause reductions in the aerosol concentration of nitrate, chloride, ammonium and sodium as well as in the total aerosol mass concentration. The sulfate produced during fog episodes favors the aerosol particles that have access to most of the fog liquid water which are usually the large particles. Aerosol scavenging efficiencies of around 80% were calculated for urban fogs. Sampling and subsequent mixing of fog droplets of different sizes may result in measured concentrations that are not fully representative of the fogwater chemical composition and can introduce errors in the reported values of the ionic species deposition velocities. Differences in the major ionic species deposition velocities can be explained by their distribution over the aerosol size spectrum and can be correlated with the species average diameter.\r\n\r\nThe second part of this work was focused on the experimental study of the mechanisms of formation of secondary aerosol particles due to the atmospheric photooxidation of hydrocarbons. In this smog chamber the aerosol forming potential of natural hydrocarbons was investigated. Natural hydrocarbons like the monoterpenes C10H16 and isoprene C5H8 are emitted by various trees and plants in significant quantities. Isoprene and [Beta]-pinene, at concentration levels ranging from a few ppb to a few ppm were reacted photoehemically with NOx, in the Caltech outdoor smog chamber facility. Aerosol formation from the isoprene photooxidation was found to be negligible even under extreme ambient conditions due to the relatively high vapor pressure of its condensable products. Aerosol carbon yield from the [Beta]-pinene photooxidation is as high as 8% and depends strongly on the initial HC/NOx ratio. The average vapor pressure of the [Beta]-pinene aerosol is estimated to be 37 [plus or minus] 24 ppt at 31?c. Monoterpene photooxidation can be a significant source of secondary aerosol in rural environments and in urban areas with extended natural vegetation.", "doi": "10.7907/Z6AN-AJ83", "publication_date": "1991", "thesis_type": "phd", "thesis_year": "1991" }, { "id": "thesis:2686", "collection": "thesis", "collection_id": "2686", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06222005-162441", "primary_object_url": { "basename": "Huang_dd-t_1991.pdf", "content": "final", "filesize": 10584952, "license": "other", "mime_type": "application/pdf", "url": "/2686/1/Huang_dd-t_1991.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Aerosol coagulation and nucleation", "author": [ { "family_name": "Huang", "given_name": "David Da-Teh", "clpid": "Huang-D-D" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Brady", "given_name": "John F.", "clpid": "Brady-J-F" }, { "family_name": "Okuyama", "given_name": "Kikuo", "clpid": "Okuyama-K" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "For aerosol Brownian coagulation in the transition regime of Knudsen number in the presence of an interparticle potential, the Fokker-Planck equation is solved by using the Grad's 13-moment method. The mass and energy accommodation coefficients that are used to describe the results of collisional processes are appropriately defined and interfaced with the Fokker-Planck moment equations. Analytical and numerical solutions of the number and energy flux profiles for the potential-free, power-law potential, van der Waals potential, and Coulombic potential situations are obtained. The results are in good agreement with those predicted by the flux-matching method of Fuchs. The present fundamental approach, therefore, provides theoretical support of the coagulation coefficient expression obtained by the empirical flux-matching method.\n \nFor coagulation between ultrafine particles, we solved the BGK equation for large but finite Knudsen number situations by taking into account the van der Waals potential and/or the Coulombic/image potential. We present closed form best-fit equations for data calculated from the theory. The conditions where either Coulombic, image, or van der Waals forces predominate are determined.\n\nA new expression of the image potential between a charged particle and an uncharged particle is obtained. We calculate the coagulation rate between the particles and are able to determine the enhancement of coagulation rate due to the interparticle potential in all size regimes.\n\nAn aerosol coagulation process is applied to the formation of aerosol particles in the semiconductor thin film preparation. In the CVD reactor, we consider simultaneous aerosol coagulation, diffusion, and generation of aerosol monomers by chemical reaction. The mass and number concentration of monomers and particles are computed as functions of temperature, pressure, input vapor concentration, and position in the reactor. The thin film growth rate can be subsequently evaluated. It is found that under certain circumstances, aerosol particle generation may significantly suppress the film growth due to monomers.\n\nThe formulation of the homogeneous nucleation free energy change of aerosol clusters is reexamined. It is shown that the inclusion of the cluster translational and rotational motion in the cluster formation free energy change is appropriate. The classical and statistical thermodynamics are shown to be consistent.\n\nThe cell model of liquids of statistical mechanics is employed to reevaluate the free energy change of cluster formation in aerosol nucleation. We provide a new molecular level theory that is applicable in the larger cluster size range where liquid-like properties begin to emerge and a cluster surface is present. The microcluster surface tension can be appropriately defined. The cluster rotational contribution to the free energy change, though it must be accounted for, is shown to be insignificant for liquid-like clusters.\n", "doi": "10.7907/G2RC-S602", "publication_date": "1991", "thesis_type": "phd", "thesis_year": "1991" }, { "id": "thesis:2910", "collection": "thesis", "collection_id": "2910", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-07172007-083859", "primary_object_url": { "basename": "Wexler_as_1991.pdf", "content": "final", "filesize": 6480009, "license": "other", "mime_type": "application/pdf", "url": "/2910/1/Wexler_as_1991.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Inorganic Components of Atmospheric Aerosols", "author": [ { "family_name": "Wexler", "given_name": "Anthony Stein", "clpid": "Wexler-Anthony-Stein" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Pandis", "given_name": "Spyros N.", "clpid": "Pandis-S-N" }, { "family_name": "Brennen", "given_name": "Christopher E.", "clpid": "Brennen-C-E" }, { "family_name": "Hunt", "given_name": "Melany L.", "clpid": "Hunt-M-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The inorganic components comprise 15% to 50% of the mass of atmospheric aerosols and, these along with the relative humidity, control the aerosol water content. For about the past 10 years the mass of the inorganic components of atmospheric aerosol was predicted assuming thermodynamic equilibrium between the volatile aerosol-phase inorganic species, NH4NO3 and NH4Cl, and their gas-phase counterparts, NH3, HNO3, and HCl. In this thesis I examine this assumption and prove that 1) the time scales for equilibration between the gas and aerosol phases are often too long for equilibrium to hold, and 2) even when equilibrium holds, transport considerations often govern the size distribution of these aerosol components.
\r\n\r\nWater can comprise a significant portion of atmospheric aerosols under conditions of high relative humidity, whereas under conditions of sufficiently low relative humidity atmospheric aerosols tend to be dry. The deliquescence point is the relative humidity where the aerosol goes from a solid dry phase to an aqueous or mixed solid-aqueous phase. Previous to this thesis little had been known about the temperature and composition dependence of the deliquescence point. In this thesis I first derive an expression for the temperature dependence of the deliquescence point and then prove that in multicomponent solutions the deliquescence point is lower than in the deliquescence point of the individual single component solutions.
\r\n\r\nThese theories of the transport, thermodynamic, and deliquescent properties of atmospheric aerosols are integrated into an aerosol inorganics model, AIM. The equilibrium predictions of AIM compare well to fundamental thermodynamic measurements. Comparison of the prediction of AIM to those of other aerosol equilibrium models show substantial disagreement in the predicted water content at lower relative humidities. The difference is due to the improved treatment of the deliquescence properties of mixed solute aerosols that is contained in AIM.
\r\n\r\nIn the summer and fall of 1987 the California Air Resources Board conducted the Southern California Air Quality Study, SCAQS. During this study the atmospheric aerosols were measured at nine sites in the Los Angeles air basin. The measurements determined the size and composition distributions of the components of the aerosol and the concentrations of their gas phase counterparts during a series of intensive study periods. The comparison of these SCAQS measurements to the predictions of AIM have so much scatter that a departure from equilibrium, that can be attributed to transport limitations, cannot be discerned. When the measured size distributions are compared as another indication of transport-limited departure from equilibrium, we find that different size aerosol particles are not in mutual equilibrium. Although the SCAQS data do not indicate a transport-limited departure from equilibrium, they do support our hypothesis that transport considerations are essential to predicting the size distribution of the volatile inorganic species.
", "doi": "10.7907/EYF6-3M05", "publication_date": "1991", "thesis_type": "phd", "thesis_year": "1991" }, { "id": "thesis:2861", "collection": "thesis", "collection_id": "2861", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-07122007-131336", "primary_object_url": { "basename": "Rogak_sn_1991.pdf", "content": "final", "filesize": 45204556, "license": "other", "mime_type": "application/pdf", "url": "/2861/1/Rogak_sn_1991.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Aerosol dynamics of agglomerates", "author": [ { "family_name": "Rogak", "given_name": "Steven Nicholas", "clpid": "Rogak-S-N" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Fultz", "given_name": "Brent T.", "clpid": "Fultz-B-T" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The mobility, charging, coagulation and mass-transfer properties of aerosol agglomerates were related to the particle and the background gas mean free path \u03bb. The mobility-equivalent diameter dm of a self-similar cluster of spheres in the continuum regime \u03bb<<dm was calculated to be proportional to the radius of gyration Rg of the cluster for fractal dimension Df>1.3. Slender-body behavior is approached for Df<1.3. In the free-molecule regime dm<<\u03bb, dm is nearly equal to the projected-area diameter dA. In the transition regime dm~\u03bb, dm depends on both dA and Rg. In general, there is a divergence of dA and Rg as the agglomerate size increases, but it is very gradual for typical aerosol agglomerates, for which dm~dA in the transition regime.
\r\n\r\nThe mass transfer of nanometer-sized 211Pb clusters to TiO2 agglomerates was investigated with an Epiphaniometer. The measured mass-transfer-equivalent diameters of the agglomerates were within 10% of dm. The lead cluster mean free path was nearly the same as \u03bb. For an analogous phenomenon, the bipolar diffusion charging of agglomerates, it was found that the charging-equivalent diameter of the agglomerates was ~10% larger than dm.
\r\n\r\nThese measurements were incorporated into a model describing the coagulation of agglomerates in the transition regime. Particles smaller than the primary particle diameter d1 were assumed to coalesce rapidly, while large particles were assumed to be solid with a fractal structure. In the transition regime, the agglomerate mean free paths are much smaller than dm even when dm<\t\u03bb. This leads to distinctly different dynamic behavior than predicted by previous models developed for the continuum or free-molecule regimes. The enhancement of coagulation over that of dense spheres is large for aerosols with median diameters slightly greater than d1 but smaller for aerosols consisting of much larger particles.
\r\n", "doi": "10.7907/PVDQ-PN74", "publication_date": "1991", "thesis_type": "phd", "thesis_year": "1991" }, { "id": "thesis:936", "collection": "thesis", "collection_id": "936", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03122007-105616", "primary_object_url": { "basename": "Nguyen_hv_1989.pdf", "content": "final", "filesize": 6335020, "license": "other", "mime_type": "application/pdf", "url": "/936/1/Nguyen_hv_1989.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Powder production in aerosol reactors : particle structure and reactor optimization", "author": [ { "family_name": "Nguyen", "given_name": "Hung Viet", "clpid": "Nguyen-H-V" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Powders consisting of dense, nonagglomerated, roughly spherical particles with a controlled size distribution are thought to be ideal for engineering applications of ceramic materials. The production of such powders in aerosol reactors is difficult due to the extreme difficulty of controlling particle formation by homogeneous nucleation of condensible vapors produced by gas phase chemical reactions. To generate the quality of powders necessary for engineering applications, one needs to understand the processes governing particle formation and growth in aerosol reactors.\n\nHomogeneous and heterogeneous nucleation were studied in a laminar flow aerosol generator using dibutylphthalate vapor. Seed particles were found to suppress homogeneous nucleation to an extent depending on their concentration. With additional insights on nucleation and nucleation suppression, aerosol physics was applied to an effort to generate dense, spherical silicon particles in a single stage multi-zone externally heated aerosol reactor. Subsequent experiments revealed that the dense silicon particles generated resulted from the sintering of aggregates formed by coagulation of like-sized particles. While the production of dense particles by sintering of low density agglomerates are feasible for low melting materials, it is not practical for refractory materials due to the high sintering temperatures required for complete coalescence in the available residence time. To produce ideal refractory powder materials, growth must be limited to vapor and small cluster deposition. An optimization technique was applied to the highly nonlinear aerosol reactor system to directly derive optimal temperature profiles that maximizes seed growth while minimizing the amount of fine particles formed. ", "doi": "10.7907/qk6a-e067", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:968", "collection": "thesis", "collection_id": "968", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03162007-091347", "primary_object_url": { "basename": "Makhlouf_em_1990.pdf", "content": "final", "filesize": 5098696, "license": "other", "mime_type": "application/pdf", "url": "/968/1/Makhlouf_em_1990.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Estimation of absolute permeability in multilayered petroleum reservoirs with two- and three-phase flow", "author": [ { "family_name": "Makhlouf", "given_name": "Eliana Mary", "clpid": "Makhlouf-E-M" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "abstract": "A numerical algorithm is developed to estimate absolute permeability in multiphase, multilayered petroleum reservoirs based upon noisy observation data, such as pressure, water cut, gas-oil ratio and rates of liquid and gas production from individual layers. The industrial Black-Oil code, CLASS, (Chevron Limited Application Simulation System), is used as the basic reservoir simulator in conjunction with this history matching algorithm. Since the history matching inverse problem is ill-posed due to its large dimensionality and the insensitivity of the permeability to measured well data, regularization and spline approximation of the spatially varying absolute permeability are employed to render the problem computationally well behaved. A stabilizing functional with a gradient operator is used to measure the non-smoothness of the parameter estimates in the regularization approach, and the regularization parameter is determined automatically during the computation. The numerical minimization algorithm is based on the partial conjugate gradient method of Nazareth. Numerical examples are considered in two- and three-phase reservoirs with three layers. The effects of the degree of regularization, spline approximation versus zonation, and differing true areal permeability distributions on the performance of the method are considered", "doi": "10.7907/DSSD-N155", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:4602", "collection": "thesis", "collection_id": "4602", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11192007-092214", "primary_object_url": { "basename": "Yin_f_1990.pdf", "content": "final", "filesize": 9132299, "license": "other", "mime_type": "application/pdf", "url": "/4602/1/Yin_f_1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Atmospheric photooxidation of organosulphur compounds", "author": [ { "family_name": "Yin", "given_name": "Fangdong", "clpid": "Yin-F" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Grosjean", "given_name": "Daniel", "clpid": "Grosjean-D" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Grosjean", "given_name": "Daniel", "clpid": "Grosjean-D" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\n\nThe atmospheric chemistry of organosulfur compounds is of fundamental importance to understanding the biogeochemical sulfur cycle as well as environmental issues such as acid precipitation and sulfur aerosol formation in the atmosphere. The research goal of the present work is to elucidate the atmospheric reaction mechanisms of conversion of organosulfur compounds to sulfur-containing aerosols.\n\nBased on the fundamental chemistry and the available kinetic and mechanistic information from experimental studies, detailed chemical reaction mechanisms have been developed for the atmospheric photooxidation of dimethyl sulfide, [...], dimethyl disulfide, [...], methanethiol, [...], and diethyl sulfide, [...]. Predictions of the developed mechanisms by computer simulation are compared with available data on laboratory photooxidation of organosulfur compounds to identify critical uncertainties in chemical pathways and reaction rate constants. Further experimental studies have been designed based on the findings from computer modeling work. Using the outdoor smog chamber reactor, the dynamic behavior of various chemical species and particle nucleation and growth have been investigated in detail under well-defined atmospheric conditions for systems [...] and [...]. Through analysis of the experimental data from outdoor smog chamber experiments by computer simulation, the mechanisms developed for photooxidation of [...] and [...] have been evaluated and reformulated. The key problems regarding the initial reactions, secondary reactions of RSOX radicals and [...] radicals, and the major chemical pathways for the formation of [...] and [...] compounds have been elucidated and the discrepancies of the experimental results between different investigators have been resolved. Critical uncertatinties regarding chemical path- ways and reaction rate constants have been identified and further detailed kinetic experimental studies have been recommended.\n", "doi": "10.7907/9gn5-p598", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:520", "collection": "thesis", "collection_id": "520", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02062007-104756", "type": "thesis", "title": "Area, Cost and Resilience Targets for Heat Exchanger Networks", "author": [ { "family_name": "Colberg", "given_name": "Richard Dale", "clpid": "Colberg-Richard-Dale" } ], "thesis_advisor": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" } ], "thesis_committee": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis presents improved area and capital cost targets for synthesis of heat exchanger networks (HEN) for fixed operating conditions, and a new resilience target for synthesis of HENs for changing, uncertain operating conditions. In addition, methods are presented to predict, before synthesis, the trade-off between cost and resilience.
\r\n\r\nA pair of \"transshipment\" nonlinear programs (NLP) is formulated to calculate the area and capital cost targets for HEN synthesis with unequal heat transfer coefficients and different capital cost laws (for different materials of construction, pressure ratings, etc.) when there are constraints on the number of matches, forbidden matches, and required matches with specified areas (for revamp synthesis). With these NLPs, the trade-off between area and number of units can be evaluated before synthesis. In addition to the targets themselves, solution of the NLPs yields \"ideal\" temperature profiles (much like the composite curves) for a HEN achieving the targets, and a selection of stream matches and their heat loads which provide an excellent starting point for synthesis of HENs achieving (within a few percent) the area and capital cost targets.
\r\n\r\nFor changing or uncertain operating conditions, a Class 1 resilience target is presented which predicts, given the nominal operating conditions, the largest uncertainty range for which a \"practical\" HEN (with few more units and stream splits than that required for nominal conditions) can be synthesized. This resilience target also predicts whether trade-offs (in utilities, number of units, or size of uncertainty range) must be made to achieve resilience, and the operating condition and constraint most likely to limit resilience.
\r\n\r\nA nonlinear program is formulated to calculate the Class 1 HEN resilience target. Trade-offs with minimum approach temperature, utility consumption, and nominal network area are presented. The use of the Class 1 resilience target as a synthesis tool is discussed.
\r\n\r\nFinally, a simple procedure to predict the trade-off between cost and resilience is introduced so that a process engineer can design for an economically \"optimal\" amount of resilience.
", "doi": "10.7907/pndd-bc72", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:625", "collection": "thesis", "collection_id": "625", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02132007-092817", "type": "thesis", "title": "Experimental and Theoretical Studies of Binary Nucleation and Condensation", "author": [ { "family_name": "Kreidenweis-Dandy", "given_name": "Sonia Maria", "clpid": "Kreidenweis-Dandy-Sonia-Maria" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Grosjean", "given_name": "Daniel", "clpid": "Grosjean-D" }, { "family_name": "Okuyama", "given_name": "Kikuo", "clpid": "Okuyama-K" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Many gas-to-particle conversion processes occurring in the atmosphere (and in technological applications) involve more than one gaseous species. An understanding of how gas-to-particle conversion occurs in multicomponent systems is necessary to predict the evolution of atmospheric aerosols. Of particular interest is the validity of binary nucleation theory in describing particle formation from two interacting vapors.
\r\n\r\nChapter II presents a modeling study of heat and mass transfer to aqueous droplets dried under various conditions, and discusses the applicability of common assumptions in describing such processes. A method for the separation, into droplets containing different solutes, of an aerosol composed of two types of aqueous droplets is proposed.
\r\n\r\nNext, in Chapter III, an experimental study of binary nucleation theory using two similar organics (dibutylphthalate and dioctylphthalate) is presented, and compared with the predictions of an integral model that describes particle formation using binary nucleation theory. It was found that the number concentrations of particles formed in the presence of both vapors was higher than could be attributed to single-component nucleation of either organic, suggesting that binary nucleation was the mechanism for particle formation. Model predictions using the theoretical binary nucleation rates, modified by suitable (species-dependent) enhancement factors, were able to represent the data well.
\r\n\r\nAttention was next focused on an environmentally-important organosulfur compound, dimethylsulfide, and its oxidation under atmospheric-type conditions. In particular, the aerosol-forming ability of the two major sulfur containing products, methanesulfonic acid and sulfuric acid, was investigated theoretically. Binary nucleation and multicomponent condensation theories were used to predict particle formation and growth in the chemically reacting system at 36% relative humidity, and model predictions were compared with published experimental smog chamber measurements of dimethylsulfide photooxidation. It was found that the experimental results could be well represented by a model that allowed for binary nucleation of aqueous sulfuric acid droplets, and ternary growth of these droplets by condensation of water, methanesulfonic acid, and sulfuric acid vapors. This investigation is presented in Chapter IV.
\r\n\r\nThe calculations presented in Chapter IV are some of the first estimates of particle formation in the methanesulfonic acid/water binary vapor system. In order to assess the validity of binary nucleation theory in describing this particle formation, an experimental program was initiated for the investigation of binary nucleation phenomena in this system. A continuous-flow, mixing-type device was proposed that would yield information not only on the critical saturation ratios required for observable particle formation, but the actual variation of nucleation rate with the gas-phase concentration of each species. The experimental apparatus that was constructed and used for this purpose and a summary and analysis of the experimental results are found in Chapter V. Particle formation was observed at moderate relative humidities and undersaturated acid vapor concentrations, demonstrating that methanesulfonic acid is able to undergo binary nucleation with water vapor. The adequacy of classical binary nucleation theory in predicting the nucleation rates is discussed in detail. The second major goal of the experimental program that was realized was the demonstration of the usefulness of this device in the investigation of binary nucleation phenomena, particularly for corrosive materials, which are difficult to work with in conventional systems.
\r\n\r\nBecause of its successful application to the methanesulfonic acid/water vapor system, this device shows great promise for future applications in the study of binary nucleation phenomena. Suggestions for the modification and improvement of the apparatus that emerged from laboratory experience and from the data analysis are presented in Chapter VI.
", "doi": "10.7907/pmy6-3d94", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:576", "collection": "thesis", "collection_id": "576", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02092007-144249", "type": "thesis", "title": "Mathematical Modeling and Control of Pollutant Dynamics in Indoor Air", "author": [ { "family_name": "Nazaroff", "given_name": "William W.", "clpid": "Nazaroff-William-W" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "To assess the total human-health and material-damage risks associated with air-pollutant exposure, the concentrations and fates of pollutants in indoor atmospheres must be understood. Three observations reinforce this point: (1) concentrations of many pollutants are commonly higher in indoor air than in outdoor air, (2) in many countries, people spend more time indoors than outside; and (3) many of the most precious material possessions of society are kept indoors. In this thesis, mathematical models are developed as tools to improve the understanding of pollutant dynamics in indoor air. These tools are applied to the problem of protecting works of art from damage due to air pollutant exposure, particularly for the purpose of understanding how to control soiling due to airborne particle deposition.
\r\n\r\nA deterministic mathematical model first is formulated to describe the time-dependent concentrations of chemically reactive gases and airborne particles in indoor air, then implemented as a computer program. Using a flexible, multichamber description of a building, the model accounts for the effects of ventilation, filtration, deposition onto surfaces, and direct emission for all pollutants. In addition, the influence of homogeneous photolytic and thermal chemical reactions is computed for gases that are present in the photochemical smog system. The model is capable of determining the chemical composition and size distribution of indoor aerosols, accounting for the effect of coagulation in addition to the processes itemized above. The model computes the fate of pollutants in indoor air, determining the absolute strengths of the sources and sinks for each species.
\r\n\r\nTo permit the simulation of soiling problems, modeling calculations for the deposition of particles and other pollutants onto surfaces are particularly detailed. Equations that predict the rate of pollutant deposition onto indoor surfaces are developed, accounting for the effects of advection, diffusion, and, for particles, gravitational settling and thermophoresis. Three air flow regimes are analyzed: natural convection induced by a temperature difference between the surface and the nearby air, forced laminar flow parallel to a surface, and homogeneous turbulence in the core of the room. The analysis of a vertical isothermal flat plate in natural convection flow shows that, for this flow regime, thermophoresis is an important particle transport process within the boundary layer adjacent to the surface, effectively repelling particles larger than approximately 0.1 \u00b5m in diameter if the surface is even a few degrees K warmer than the nearby air.
\r\n\r\nTo test model performance, and to investigate the dynamic behavior of indoor pollutants, the model is applied to several indoor air quality problems. In one case, modeling predictions are made of pollutant concentrations in a museum gallery in Southern California into which photochemical smog is introduced by the ventilation system. Good agreement is obtained between measured and modeled concentrations of NO, NO\u2082 and O\u2083. The model predicts substantial production of several species, including HNO\u2082, HNO\u2083, NO\u2083, and N\u2082O\u2085, due to chemical reaction within the museum atmosphere. The aerosol mechanics aspects are tested by applying the model to the problem of predicting the evolution of the aerosol size distribution following combustion of a cigarette in a single room having a low air-exchange rate, and good agreement is found between model predictions and measured values.
\r\n\r\nThe completed indoor air quality model next is used to evaluate the soiling hazard to art objects in museums resulting from the deposition of particles containing elemental carbon (soot) or soil dust. Time-resolved measurements of the indoor and outdoor aerosol size distribution in three Southern California museums are reported. Model predictions of indoor aerosol characteristics based on measured outdoor aerosol characteristics and data on building dynamics agree well with measurements. The predictions also show that generally less than 1% of the fine particles (0.05-2 \u00b5m in diameter) entering the museums deposit onto the walls. Nevertheless, deposition calculations indicate that, at the rates determined for the study days, elemental carbon (soot) particles would accumulate on vertical surfaces in the museums at a rate sufficient to yield perceptible soiling in characteristic times of 1-40 years, depending on the museum studied. These are very short periods, considering that many art objects are to be preserved indefinitely.
\r\n\r\nTo test the accuracy of the particle deposition calculations, model predictions are made of the annual mean deposition velocity of particles onto the walls of five Southern California museums, using the results of short-term monitoring of near-wall air velocities and long-term monitoring of surface-air temperature differences. The predictions are compared against the results of measurements in these museums of the deposition velocities of sulfates and of fine particles. The modeling and measurement results generally concur, revealing that the deposition velocities for a given particle size vary by a factor of as much as 30 among the sites studied, with the lowest values associated with laminar forced flow adjacent to the building walls, and highest values found in museums where deposition is driven by turbulence in the core of the room.
\r\n\r\nMethods for reducing the soiling rate of objects displayed in museums are identified and include the following: (1) reducing the rate of supply of outdoor air into the building; (2) increasing the effectiveness of particle filtration; (3) altering the air flow conditions within the building to reduce the particle deposition velocity onto surfaces of concern; (4) placing objects within display cases or framing objects behind glass; (5) managing the building site to achieve low outdoor concentrations; and (6) eliminating indoor particle sources. The mathematical model of indoor aerosol dynamics is combined with experimental data collected at an historic museum in Southern California to determine the potential effectiveness of these control measures. According to model results, with careful design of control measures the soiling rate can be reduced by at least two orders of magnitude, thereby extending to periods of a century or more the time before noticeable soiling will occur.
", "doi": "10.7907/89WP-N863", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:520", "collection": "thesis", "collection_id": "520", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02062007-104756", "type": "thesis", "title": "Area, Cost and Resilience Targets for Heat Exchanger Networks", "author": [ { "family_name": "Colberg", "given_name": "Richard Dale", "clpid": "Colberg-Richard-Dale" } ], "thesis_advisor": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" } ], "thesis_committee": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis presents improved area and capital cost targets for synthesis of heat exchanger networks (HEN) for fixed operating conditions, and a new resilience target for synthesis of HENs for changing, uncertain operating conditions. In addition, methods are presented to predict, before synthesis, the trade-off between cost and resilience.
\r\n\r\nA pair of \"transshipment\" nonlinear programs (NLP) is formulated to calculate the area and capital cost targets for HEN synthesis with unequal heat transfer coefficients and different capital cost laws (for different materials of construction, pressure ratings, etc.) when there are constraints on the number of matches, forbidden matches, and required matches with specified areas (for revamp synthesis). With these NLPs, the trade-off between area and number of units can be evaluated before synthesis. In addition to the targets themselves, solution of the NLPs yields \"ideal\" temperature profiles (much like the composite curves) for a HEN achieving the targets, and a selection of stream matches and their heat loads which provide an excellent starting point for synthesis of HENs achieving (within a few percent) the area and capital cost targets.
\r\n\r\nFor changing or uncertain operating conditions, a Class 1 resilience target is presented which predicts, given the nominal operating conditions, the largest uncertainty range for which a \"practical\" HEN (with few more units and stream splits than that required for nominal conditions) can be synthesized. This resilience target also predicts whether trade-offs (in utilities, number of units, or size of uncertainty range) must be made to achieve resilience, and the operating condition and constraint most likely to limit resilience.
\r\n\r\nA nonlinear program is formulated to calculate the Class 1 HEN resilience target. Trade-offs with minimum approach temperature, utility consumption, and nominal network area are presented. The use of the Class 1 resilience target as a synthesis tool is discussed.
\r\n\r\nFinally, a simple procedure to predict the trade-off between cost and resilience is introduced so that a process engineer can design for an economically \"optimal\" amount of resilience.
", "doi": "10.7907/pndd-bc72", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:576", "collection": "thesis", "collection_id": "576", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02092007-144249", "type": "thesis", "title": "Mathematical Modeling and Control of Pollutant Dynamics in Indoor Air", "author": [ { "family_name": "Nazaroff", "given_name": "William W.", "clpid": "Nazaroff-William-W" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "To assess the total human-health and material-damage risks associated with air-pollutant exposure, the concentrations and fates of pollutants in indoor atmospheres must be understood. Three observations reinforce this point: (1) concentrations of many pollutants are commonly higher in indoor air than in outdoor air, (2) in many countries, people spend more time indoors than outside; and (3) many of the most precious material possessions of society are kept indoors. In this thesis, mathematical models are developed as tools to improve the understanding of pollutant dynamics in indoor air. These tools are applied to the problem of protecting works of art from damage due to air pollutant exposure, particularly for the purpose of understanding how to control soiling due to airborne particle deposition.
\r\n\r\nA deterministic mathematical model first is formulated to describe the time-dependent concentrations of chemically reactive gases and airborne particles in indoor air, then implemented as a computer program. Using a flexible, multichamber description of a building, the model accounts for the effects of ventilation, filtration, deposition onto surfaces, and direct emission for all pollutants. In addition, the influence of homogeneous photolytic and thermal chemical reactions is computed for gases that are present in the photochemical smog system. The model is capable of determining the chemical composition and size distribution of indoor aerosols, accounting for the effect of coagulation in addition to the processes itemized above. The model computes the fate of pollutants in indoor air, determining the absolute strengths of the sources and sinks for each species.
\r\n\r\nTo permit the simulation of soiling problems, modeling calculations for the deposition of particles and other pollutants onto surfaces are particularly detailed. Equations that predict the rate of pollutant deposition onto indoor surfaces are developed, accounting for the effects of advection, diffusion, and, for particles, gravitational settling and thermophoresis. Three air flow regimes are analyzed: natural convection induced by a temperature difference between the surface and the nearby air, forced laminar flow parallel to a surface, and homogeneous turbulence in the core of the room. The analysis of a vertical isothermal flat plate in natural convection flow shows that, for this flow regime, thermophoresis is an important particle transport process within the boundary layer adjacent to the surface, effectively repelling particles larger than approximately 0.1 \u00b5m in diameter if the surface is even a few degrees K warmer than the nearby air.
\r\n\r\nTo test model performance, and to investigate the dynamic behavior of indoor pollutants, the model is applied to several indoor air quality problems. In one case, modeling predictions are made of pollutant concentrations in a museum gallery in Southern California into which photochemical smog is introduced by the ventilation system. Good agreement is obtained between measured and modeled concentrations of NO, NO\u2082 and O\u2083. The model predicts substantial production of several species, including HNO\u2082, HNO\u2083, NO\u2083, and N\u2082O\u2085, due to chemical reaction within the museum atmosphere. The aerosol mechanics aspects are tested by applying the model to the problem of predicting the evolution of the aerosol size distribution following combustion of a cigarette in a single room having a low air-exchange rate, and good agreement is found between model predictions and measured values.
\r\n\r\nThe completed indoor air quality model next is used to evaluate the soiling hazard to art objects in museums resulting from the deposition of particles containing elemental carbon (soot) or soil dust. Time-resolved measurements of the indoor and outdoor aerosol size distribution in three Southern California museums are reported. Model predictions of indoor aerosol characteristics based on measured outdoor aerosol characteristics and data on building dynamics agree well with measurements. The predictions also show that generally less than 1% of the fine particles (0.05-2 \u00b5m in diameter) entering the museums deposit onto the walls. Nevertheless, deposition calculations indicate that, at the rates determined for the study days, elemental carbon (soot) particles would accumulate on vertical surfaces in the museums at a rate sufficient to yield perceptible soiling in characteristic times of 1-40 years, depending on the museum studied. These are very short periods, considering that many art objects are to be preserved indefinitely.
\r\n\r\nTo test the accuracy of the particle deposition calculations, model predictions are made of the annual mean deposition velocity of particles onto the walls of five Southern California museums, using the results of short-term monitoring of near-wall air velocities and long-term monitoring of surface-air temperature differences. The predictions are compared against the results of measurements in these museums of the deposition velocities of sulfates and of fine particles. The modeling and measurement results generally concur, revealing that the deposition velocities for a given particle size vary by a factor of as much as 30 among the sites studied, with the lowest values associated with laminar forced flow adjacent to the building walls, and highest values found in museums where deposition is driven by turbulence in the core of the room.
\r\n\r\nMethods for reducing the soiling rate of objects displayed in museums are identified and include the following: (1) reducing the rate of supply of outdoor air into the building; (2) increasing the effectiveness of particle filtration; (3) altering the air flow conditions within the building to reduce the particle deposition velocity onto surfaces of concern; (4) placing objects within display cases or framing objects behind glass; (5) managing the building site to achieve low outdoor concentrations; and (6) eliminating indoor particle sources. The mathematical model of indoor aerosol dynamics is combined with experimental data collected at an historic museum in Southern California to determine the potential effectiveness of these control measures. According to model results, with careful design of control measures the soiling rate can be reduced by at least two orders of magnitude, thereby extending to periods of a century or more the time before noticeable soiling will occur.
", "doi": "10.7907/89WP-N863", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:629", "collection": "thesis", "collection_id": "629", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02132007-152409", "type": "thesis", "title": "The Chemical Composition of Fogs and Clouds in Southern California", "author": [ { "family_name": "Munger", "given_name": "James William", "clpid": "Munger-James-William" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Fogs and clouds are frequent occurrences in Southern California. Their chemical composition is of interest due to their potential role in the transformation of sulfur and nitrogen oxides to sulfuric and nitric acid and in the subsequent deposition of those acids. In addition, cloud and fog droplets may be involved in the chemistry of low-molecular-weight carboxylic acids and carbonyl compounds.
\r\n\r\nThe major inorganic species in cloud and fogwater samples were NH\u2084\u207a, H\u207a, NO\u2083\u207b, and SO\u2084\u00b2\u207b. Concentrations in fogwater samples were 1-10 x 10\u207b\u00b3 M; pH values ranged from \u22432 to 6. Nitrate usually exceeded sulfate. Acidity depended on the availability of NH\u2083 from agricultural operations. Stratus cloudwater had somewhat lower concentrations; pH values were in the range 3 - 4. The major factors accounting for variation in fog- or cloudwater composition were the preexisting aerosol and gas concentrations and variations in liquid water content. Deposition and entrainment or advection of different air masses were also important during extended cloud or fog episodes.
\r\n\r\nThe droplet size dependence of cloudwater composition was investigated on one occasion in an intercepted coastal stratus clouds. The observations were consistent with the hypothesis that small droplets form on small secondary aerosol composed of H\u2082SO\u2084, HNO\u2083 and their NH\u2084\u207a salts, while large droplets form on large sea-salt and soil-dust aerosol. Species that can exist in the gas phase, such as HCl and HNO\u2083, may be found in either droplet-size fraction.
\r\n\r\nConcentrations of S(IV) and CH\u2082O in the range 100 - 1000 \u00b5M were observed in fogwater from urban sites in Southern California. Lower concentrations were observed in stratus clouds. The high levels of S(IV) and CH\u2082O were attributed to the formation of hydroxymethanesulfonate (HMSA), the S(IV) adduct of CH\u2082O. Direct measurement of HMSA in fogwater samples from Bakersfield, CA were made by ion-pairing chromatography. Glyoxal and methyiglyoxal were observed at concentrations comparable to CH\u2082O in fogwater samples from Riverside, CA and in stratus cloudwater samples from sites along the Santa Barbara Channel.
", "doi": "10.7907/YFER-M388", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:629", "collection": "thesis", "collection_id": "629", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02132007-152409", "type": "thesis", "title": "The Chemical Composition of Fogs and Clouds in Southern California", "author": [ { "family_name": "Munger", "given_name": "James William", "clpid": "Munger-James-William" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Yung", "given_name": "Yuk L.", "orcid": "0000-0002-4263-2562", "clpid": "Yung-Y-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Fogs and clouds are frequent occurrences in Southern California. Their chemical composition is of interest due to their potential role in the transformation of sulfur and nitrogen oxides to sulfuric and nitric acid and in the subsequent deposition of those acids. In addition, cloud and fog droplets may be involved in the chemistry of low-molecular-weight carboxylic acids and carbonyl compounds.
\r\n\r\nThe major inorganic species in cloud and fogwater samples were NH\u2084\u207a, H\u207a, NO\u2083\u207b, and SO\u2084\u00b2\u207b. Concentrations in fogwater samples were 1-10 x 10\u207b\u00b3 M; pH values ranged from \u22432 to 6. Nitrate usually exceeded sulfate. Acidity depended on the availability of NH\u2083 from agricultural operations. Stratus cloudwater had somewhat lower concentrations; pH values were in the range 3 - 4. The major factors accounting for variation in fog- or cloudwater composition were the preexisting aerosol and gas concentrations and variations in liquid water content. Deposition and entrainment or advection of different air masses were also important during extended cloud or fog episodes.
\r\n\r\nThe droplet size dependence of cloudwater composition was investigated on one occasion in an intercepted coastal stratus clouds. The observations were consistent with the hypothesis that small droplets form on small secondary aerosol composed of H\u2082SO\u2084, HNO\u2083 and their NH\u2084\u207a salts, while large droplets form on large sea-salt and soil-dust aerosol. Species that can exist in the gas phase, such as HCl and HNO\u2083, may be found in either droplet-size fraction.
\r\n\r\nConcentrations of S(IV) and CH\u2082O in the range 100 - 1000 \u00b5M were observed in fogwater from urban sites in Southern California. Lower concentrations were observed in stratus clouds. The high levels of S(IV) and CH\u2082O were attributed to the formation of hydroxymethanesulfonate (HMSA), the S(IV) adduct of CH\u2082O. Direct measurement of HMSA in fogwater samples from Bakersfield, CA were made by ion-pairing chromatography. Glyoxal and methyiglyoxal were observed at concentrations comparable to CH\u2082O in fogwater samples from Riverside, CA and in stratus cloudwater samples from sites along the Santa Barbara Channel.
", "doi": "10.7907/YFER-M388", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:697", "collection": "thesis", "collection_id": "697", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02212007-131607", "type": "thesis", "title": "Plasmid Propagation in the Yeast Saccharomyces cerevisiae: Flow Cytometry Studies and Segregated Modeling", "author": [ { "family_name": "Wittrup", "given_name": "Karl Dane", "clpid": "Wittrup-Karl-Dane" } ], "thesis_advisor": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" } ], "thesis_committee": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Campbell", "given_name": "Judith L.", "orcid": "0000-0001-8291-5551", "clpid": "Campbell-J-L" }, { "family_name": "Rothenberg", "given_name": "Ellen V.", "orcid": "0000-0002-3901-347X", "clpid": "Rothenberg-E-V" }, { "family_name": "Arnold", "given_name": "Frances Hamilton", "orcid": "0000-0002-4027-364X", "clpid": "Arnold-F-H" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The baker's yeast Saccharomyces cerevisiae is potentially a very useful host for the production of pharmaceutical proteins by recombinant DNA technology. One requirement for efficient overproduction of a foreign protein in yeast is a stable recombinant DNA vector which is maintained at a high number of copies per cell. The rational design of such vectors requires knowledge concerning their propagation in a cell population. The purpose of this work is to develop mathematical and experimental tools for the study of multicopy plasmid propagation, and to apply these tools to the investigation of a particular type of yeast vector: a conditional centromere plasmid.
\r\n\r\nA method for measuring the distribution of plasmid copy number in yeast populations was developed, using \u03b2-galactosidase activity as a marker for plasmid copy number. Enzyme activity is assayed at the single-cell level using a fluorogenic substrate and flow cytometry. The relationship between single-cell fluorescence and enzyme activity is described by a mathematical reaction-diffusion model.
\r\n\r\nA segregated mathematical modeling framework was established to link measured copy number distributions with probabilistic models of single-cell plasmid replication and partitioning. Simplifications of the general integral-partial differential population balance equations were obtained for a discrete state variable, resulting in a linear system of ordinary differential equations.
\r\n\r\nFlow cytometry and segregated modeling were applied to the study of a conditional centromere plasmid. This type of plasmid can be amplified to high copy number by unequal partitioning, but the amplified copy number state is unstable in the absence of selection pressure. A segregated model of this plasmid's propagation was shown to be consistent with experimental observations. The conceptual model of plasmid instability suggests changes in the attributes of the host cell and plasmid construction to improve stability at high copy number. A segregated mathematical model of this type is necessary for the design of bioreactor operating conditions that optimize productivity.
", "doi": "10.7907/KQYB-CX46", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:697", "collection": "thesis", "collection_id": "697", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02212007-131607", "type": "thesis", "title": "Plasmid Propagation in the Yeast Saccharomyces cerevisiae: Flow Cytometry Studies and Segregated Modeling", "author": [ { "family_name": "Wittrup", "given_name": "Karl Dane", "clpid": "Wittrup-Karl-Dane" } ], "thesis_advisor": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" } ], "thesis_committee": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Campbell", "given_name": "Judith L.", "orcid": "0000-0001-8291-5551", "clpid": "Campbell-J-L" }, { "family_name": "Rothenberg", "given_name": "Ellen V.", "orcid": "0000-0002-3901-347X", "clpid": "Rothenberg-E-V" }, { "family_name": "Arnold", "given_name": "Frances Hamilton", "orcid": "0000-0002-4027-364X", "clpid": "Arnold-F-H" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The baker's yeast Saccharomyces cerevisiae is potentially a very useful host for the production of pharmaceutical proteins by recombinant DNA technology. One requirement for efficient overproduction of a foreign protein in yeast is a stable recombinant DNA vector which is maintained at a high number of copies per cell. The rational design of such vectors requires knowledge concerning their propagation in a cell population. The purpose of this work is to develop mathematical and experimental tools for the study of multicopy plasmid propagation, and to apply these tools to the investigation of a particular type of yeast vector: a conditional centromere plasmid.
\r\n\r\nA method for measuring the distribution of plasmid copy number in yeast populations was developed, using \u03b2-galactosidase activity as a marker for plasmid copy number. Enzyme activity is assayed at the single-cell level using a fluorogenic substrate and flow cytometry. The relationship between single-cell fluorescence and enzyme activity is described by a mathematical reaction-diffusion model.
\r\n\r\nA segregated mathematical modeling framework was established to link measured copy number distributions with probabilistic models of single-cell plasmid replication and partitioning. Simplifications of the general integral-partial differential population balance equations were obtained for a discrete state variable, resulting in a linear system of ordinary differential equations.
\r\n\r\nFlow cytometry and segregated modeling were applied to the study of a conditional centromere plasmid. This type of plasmid can be amplified to high copy number by unequal partitioning, but the amplified copy number state is unstable in the absence of selection pressure. A segregated model of this plasmid's propagation was shown to be consistent with experimental observations. The conceptual model of plasmid instability suggests changes in the attributes of the host cell and plasmid construction to improve stability at high copy number. A segregated mathematical model of this type is necessary for the design of bioreactor operating conditions that optimize productivity.
", "doi": "10.7907/KQYB-CX46", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:2592", "collection": "thesis", "collection_id": "2592", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06142006-135258", "type": "thesis", "title": "A Theoretical Study of Reaction and Diffusion in Microstructured Materials", "author": [ { "family_name": "Loewenberg", "given_name": "Michael", "clpid": "Loewenberg-Michael" } ], "thesis_advisor": [ { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" } ], "thesis_committee": [ { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Brady", "given_name": "John F.", "clpid": "Brady-J-F" }, { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A fundamental study of heterogeneous reaction and diffusion in random, microstructured materials has been conducted. A detailed, ensemble averaging approach has been developed for the analysis of diffusion-controlled reactions. The method was used to determine the reactant flux into a bounded or semi-infinite medium containing a dilute suspension of reactive, spherical particles under steady-state or transient conditions. The influence of the boundary was given explicit, detailed consideration and the results were compared with a mean-field treatment. Physical motivation is provided by the process of ash vaporization during pulverized coal combustion. The analysis was subsequently extended to study the decay of an initially uniform distribution of reactant which allows comparison with other theoretical approaches. The result suggests that the present method reproduces the solution to this well-known problem by a seemingly simpler, more physical approach. The configurational averaging technique was employed in a study of heterogeneous reaction in a porous material under diffusion-controlled conditions. The porous solid is assumed to have a bimodal pore structure with a random, isotropic distribution of cylindrical macro-pores. The results are relevant to the pulverized combustion of char from softening coals. In the diffusion-controlled limit, the results coincide with a simpler, single pore model.
\r\n\r\nA simplified model of char combustion has been developed which treats pore diffusion and growth coupled to gas-phase heat and mass transport. An efficient model-based algorithm was developed for the determination of oxidation rates from combustion data. These models were applied in two studies involving well-defined laboratory combustion experiments.
\r\n", "doi": "10.7907/5tgx-2d57", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:4630", "collection": "thesis", "collection_id": "4630", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11212007-094804", "type": "thesis", "title": "Control System Design for Robust Performance Despite Model Parameter Uncertainties: Application to Cross-Directional Response Control in Paper Manufacturing", "author": [ { "family_name": "Laughlin", "given_name": "Daniel Lee", "clpid": "Laughlin-Daniel-Lee" } ], "thesis_advisor": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" } ], "thesis_committee": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Sideris", "given_name": "Athanasios", "clpid": "Sideris-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The problem of robust performance analysis is solved for SISO control systems with uncorrelated model parameter uncertainties. The robust performance problem is formulated in a manner consistent with structured singular value \u00b5-analysis - for SISO systems this means restricting the magnitude of a weighted closed-loop sensitivity function. The solution to the problem is graphical in nature and well suited to a computer-aided controller-design procedure. It utilizes region boundaries on the complex plane that contain specified sets of process models at each frequency. An algorithm is presented for locating the region boundaries corresponding to model transfer-functions with uncertain real coefficients and time-delay. Convergence and containment properties of the algorithm are proven.
\r\n\r\nThe region-based analysis is combined with the Internal Model Control design procedure to form a controller synthesis method for robust performance. Tradeoffs between performance and robustness are transparent to the designer in the proposed synthesis method. Useful tables of controller parameters are presented in tabular form for a wide range of parameter uncertainty levels in a first-order-with-time-delay model. The controller resulting from the IMC design procedure is compared with the \u00b5-optimal controller. Although the new synthesis procedure is generally applicable to SISO systems, it can be used to design decentralized controllers for MIMO systems with uncertain scalar dynamics and symmetric interactions. The particular application of cross-machine-direction basis-weight control in paper manufacturing is discussed in detail. Robust performance and robust failure tolerance of desirable decentralized controllers for this system are proven.
\r\n", "doi": "10.7907/cps9-m559", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:5148", "collection": "thesis", "collection_id": "5148", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12282004-153051", "type": "thesis", "title": "Aerosol Formation and Growth in Aromatic Hydrocarbon/NO\u2093 Systems", "author": [ { "family_name": "Stern", "given_name": "Jennifer E.", "clpid": "Stern-Jennifer-E" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Grosjean", "given_name": "Daniel", "clpid": "Grosjean-D" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The formation of secondary organic aerosol in the atmosphere remains one of the most poorly understood aspects of the air pollution problem in urban areas. Photooxidation of gas-phase emissions produces low vapor pressure species that are converted to the aerosol phase either by homogeneous nucleation of new particles or by condensation onto existing particles. One of the goals in studying aerosol dynamics in atmospheric systems is to determine the factors that govern which of these two pathways dominates in the conversion of gas-phase species to the aerosol phase.
\r\n\r\nWe have conducted an extensive series of experiments aimed at elucidating the physics of atmospheric organic aerosol formation. An outdoor smog chamber was used to study the formation and growth of secondary aerosol resulting from the photooxidation of aromatic hydrocarbons (toluene, m-xylene, ethyl benzene, and 1,3,5-trimethyl benzene) in the presence of NO\u2093. In the experiments, particular emphasis was given to the effect of primary aerosol on the subsequent aerosol evolution in the system. We observed that with a sufficient number concentration of initial seed particles in the system, homogeneous nucleation could be suppressed and all gas-to-particle conversion occurred via condensation onto the seed particles.
\r\n\r\nAerosol yields by mass from the gas phase were calculated for each experiment. These yields were somewhat dependent on the initial hydrocarbon/NO\u2093 ratio in each experiment, which is an indication of the system reactivity. Average yields for each aromatic species were: toluene - 4.8%, m-xylene - 3.5%, ethyl benzene - 1.9%, and 1,3,5-trimethyl benzene - 2.4%. These results are in good agreement with previous determinations of aerosol yield for the toluene and m-xylene systems.
\r\n\r\nSeveral models were used to describe the observed aerosol dynamics. An integral model assuming a monodisperse aerosol, developed by Warren and Seinfeld (1984, 1985b), was used to determine apparent saturation vapor pressures of condensible species from the observations of nucleation events. Overall predictions of final number concentrations with the integral model, based on these saturation vapor pressures, were fairly close to the experimentally observed number concentrations.
\r\n\r\nAn analysis of the rate of aerosol growth was carried out for those experiments exhibiting uniform condensational growth. This analysis provided estimates for the gas-phase partial pressures of the condensible species, which could be compared with the integral model vapor pressures to give approximate saturation ratios during these periods of growth.
\r\n\r\nFull aerosol size distribution simulations were performed using the sectional model ESMAP (Warren and Seinfeld, 1985a), based on the work of Gelbard et al. (1980). Number concentrations resulting from these predictions were higher than those of the integral model, since the condensation rate on a polydisperse aerosol is smaller than that on a monodisperse distribution, leading to a higher nucleation rate. Comparisons of predicted and observed size, distributions during the course of each experiment were limited in accuracy by the numerical diffusion associated with current versions of the sectional model.
", "doi": "10.7907/417v-ke62", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:5416", "collection": "thesis", "collection_id": "5416", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12042009-080025691", "type": "thesis", "title": "Use of a Continuous Stirred Tank Reactor for the Study of Aqueous Aerosol Chemistry", "author": [ { "family_name": "Adkins", "given_name": "Carol Leslie Jones", "clpid": "Adkins-Carol-Leslie-Jones" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Okuyama", "given_name": "Kikuo", "clpid": "Okuyama-K" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Atmospheric aerosol chemistry is important in areas ranging from urban air pollution to cloud formation. It has long been supposed that droplet-phase reactions account for a significant fraction of the atmospheric conversion of SO\u2082 to sulfate. Among such reactions is the manganese-catalyzed aqueous-phase oxidation of SO\u2082. Whereas the role of aqueous phase SO\u2082 oxidation in the dilute solutions characteristic of fog and cloud droplets (diameter > 10 \u00b5m) has been reasonably well established, the role of comparable reaction in submicron aerosols is uncertain. In this thesis a reactor system is developed to carry out gas-aerosol reactions under humid, ambient-like conditions. The apparatus consists of a continuous stirred tank reactor (CSTR) in which the growth of the aqueous aerosol is measured. Absence of mass transfer limitation, coagulation, and nucleation ensure that particle growth is direct evidence of reaction. Special care is taken to minimize size biasing of the aqueous aerosol in the electrostatic classifier used to measure the reactor feed and effluent distributions. Aerosol behavior in the reactor is modeled assuming an ideal CSTR and, given the solution thermodynamics and equilibrium chemistry, the effluent distribution can be predicted using one of the proposed reaction rate mechanisms.
\r\n\r\nExperiments were performed using a pure MnSO\u2084 or a MnSO\u2084-Na\u2082SO\u2084 mixture feed aerosol. The relative humidity ranged from 86 to 94% and 0.1 ppm < pSO\u2082, < 50 ppm. The slow, approximately constant reaction rate of Bronikowski and Pasiuk-Bronikowska (1981) (R ~ 2 x 10\u207b\u2074 Ms\u207b\u00b9) was found to best predict the observed growth over the entire range of operating conditions. The various rate expressions proposed for this system in the literature resulted in varying estimates of growth. When reactor conditions were similar to those at which the rate expression was determined, the agreement between the predicted and observed distributions improved. This indicates that use of a rate expression beyond its specified range may result in erroneous predictions.
\r\n", "doi": "10.7907/8cpt-ce77", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:4450", "collection": "thesis", "collection_id": "4450", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11072007-130323", "type": "thesis", "title": "The Formation Kinetics, Mechanisms, and Thermodynamics of S(IV)-Aldehyde Addition Compounds", "author": [ { "family_name": "Olson", "given_name": "Terese Marie", "clpid": "Olson-Terese-Marie" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Gray", "given_name": "Harry B.", "clpid": "Gray-H-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The reaction kinetics and thermodynamics of the reversible addition of S(IV) and several aldehydes were studied at low pH in order to determine which carbonyl-bisulfite adducts are potential S(IV) reservoirs in atmospheric water droplets. Benzaldehyde, glyoxal, glyoxylic acid, and hydroxyacetaldehyde were chosen as aldehyde substrates.
\r\n\r\nSpectrophotometric methods were employed to study the reaction kinetics. Between pH 1 - 3, the two rate-determining steps for adduct formation were the addition of HSO\u2083\u207b and SO\u2083\u00b2\u207b to the carbonyl carbon atom. The sulfite ion was a much more effective nucleophile than bisulfite; rate constants for sulfite addition are four to five orders of magnitude higher than for bisulfate. Below pH 1, some specific acid catalysis was also observed.
\r\n\r\nAdduct stability constants were determined by spectrophotometry and from microscopic reversibility relationships. Linear-free-energy relationships between carbonyl-bisulfate adduct stabilities and the Taft \u03c3* parameter were found to hold for a limited set of aldehyde substrates. A relatively high correlation exists between bisulfate adduct stability constants and carbonyl hydration constants.
\r\n\r\nCriteria were formulated, which can be used to predict the potential effectiveness of a carbonyl to significantly stabilize S(IV) in droplets. Modeling calculations for an open atmosphere show that adduct formation rates are much slower than mass transfer and S(IV) oxidation rates under most fog- and cloud-water conditions. Formation rates of hydroxyacetaldehyde-, glyoxal-, and glyoxylic acid - bisulfate addition compounds are comparable to, or faster than, formation rates of hydroxymethanesulfonate, which has been identified in droplets. Equilibrium calculations suggest that these three addition compounds can also stabilize a significant excess of SO\u2082 in the liquid phase.
\r\n", "doi": "10.7907/rpn9-8403", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:4536", "collection": "thesis", "collection_id": "4536", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11132007-082406", "type": "thesis", "title": "Mathematical Models Based on Molecular Processes of the Cell", "author": [ { "family_name": "Seressiotis", "given_name": "Alexandros", "clpid": "Seressiotis-Alexandros" } ], "thesis_advisor": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" } ], "thesis_committee": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Arnold", "given_name": "Frances Hamilton", "orcid": "0000-0002-4027-364X", "clpid": "Arnold-F-H" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Bertani", "given_name": "Giuseppe", "clpid": "Bertani-G" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A necessary first step in modeling the metabolic reaction network is a systematic procedure for determining the different reaction sequences which connect two metabolites. A software system (MPS) has been designed on the principles of artificial intelligence in order to address the problem of analysis and synthesis of metabolic pathways leading from one carbon-containing metabolite to another. MPS can be used to predict on a qualitative basis the effects of adding or deleting enzymatic activities to or from the cellular environment, to extract information about metabolic regulation, and to direct experiments in metabolic engineering. The main principles that have been used for the development of MPS are described along with case studies demonstrating the capabilities and potential applications of such a software system. The examples will examine carbon catabolic pathways and amino acid biosynthetic pathways. The catabolic pathways example concentrates on the conversion of glucose 6-phosphate to pyruvate. The output from MPS, which synthesized the classical catabolic pathways along with possible variations, leads to the identification of required genotypes/sets of enzymes that convert glucose 6-phosphate to pyruvate with different ATP and NAD(P)H coupling. The amino acid examples refer to the production of L-alanine from pyruvate and the identification of alternative pathways that perform this bioconversion.
\r\n\r\nThe appropriate use of controllable promoters and plasmid origins of replication provide an opportunity for identifying operating strategies that maximize productivity of unstable recombinant cultures. This is demonstrated by first developing a kinetic model for product formation in recombinant cultures that exhibit both segregational and structural instability, and subsequently by identifying operating conditions that maximize productivity with respect to the base case (uncontrollable promoter and plasmid origin of replication).
\r\n\r\nFinally, an approach is being made to examine the validity of traditional-macroscopic relationships for the description of equilibrium cellular processes. A model is described that addresses these processes from a statistical point of view and results of this model are compared with analogous results obtained from traditional methods applied to a subset of the reactions that characterize the control mechanisms of the lac promoter.
\r\n", "doi": "10.7907/a9re-yr49", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:4536", "collection": "thesis", "collection_id": "4536", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11132007-082406", "type": "thesis", "title": "Mathematical Models Based on Molecular Processes of the Cell", "author": [ { "family_name": "Seressiotis", "given_name": "Alexandros", "clpid": "Seressiotis-Alexandros" } ], "thesis_advisor": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" } ], "thesis_committee": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Arnold", "given_name": "Frances Hamilton", "orcid": "0000-0002-4027-364X", "clpid": "Arnold-F-H" }, { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Bertani", "given_name": "Giuseppe", "clpid": "Bertani-G" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A necessary first step in modeling the metabolic reaction network is a systematic procedure for determining the different reaction sequences which connect two metabolites. A software system (MPS) has been designed on the principles of artificial intelligence in order to address the problem of analysis and synthesis of metabolic pathways leading from one carbon-containing metabolite to another. MPS can be used to predict on a qualitative basis the effects of adding or deleting enzymatic activities to or from the cellular environment, to extract information about metabolic regulation, and to direct experiments in metabolic engineering. The main principles that have been used for the development of MPS are described along with case studies demonstrating the capabilities and potential applications of such a software system. The examples will examine carbon catabolic pathways and amino acid biosynthetic pathways. The catabolic pathways example concentrates on the conversion of glucose 6-phosphate to pyruvate. The output from MPS, which synthesized the classical catabolic pathways along with possible variations, leads to the identification of required genotypes/sets of enzymes that convert glucose 6-phosphate to pyruvate with different ATP and NAD(P)H coupling. The amino acid examples refer to the production of L-alanine from pyruvate and the identification of alternative pathways that perform this bioconversion.
\r\n\r\nThe appropriate use of controllable promoters and plasmid origins of replication provide an opportunity for identifying operating strategies that maximize productivity of unstable recombinant cultures. This is demonstrated by first developing a kinetic model for product formation in recombinant cultures that exhibit both segregational and structural instability, and subsequently by identifying operating conditions that maximize productivity with respect to the base case (uncontrollable promoter and plasmid origin of replication).
\r\n\r\nFinally, an approach is being made to examine the validity of traditional-macroscopic relationships for the description of equilibrium cellular processes. A model is described that addresses these processes from a statistical point of view and results of this model are compared with analogous results obtained from traditional methods applied to a subset of the reactions that characterize the control mechanisms of the lac promoter.
\r\n", "doi": "10.7907/a9re-yr49", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:4483", "collection": "thesis", "collection_id": "4483", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11092007-141214", "type": "thesis", "title": "Reactor Input Manipulation for Developing Models for Catalytic Reactions", "author": [ { "family_name": "Shanks", "given_name": "Brent Howard", "clpid": "Shanks-Brent-Howard" } ], "thesis_advisor": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" } ], "thesis_committee": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A variety of phenomenological experimental methods are employed to construct and validate kinetic models for heterogeneous catalytic reaction systems. Both static input and stimulus-response experiments are performed with particular emphasis placed on the novel feedback-induced bifurcation method. These techniques are applied to CO oxidation on Rh/Al\u2082O\u2083 and Ag/Al\u2082O\u2083 to identify kinetic models that are able to reproduce transient as well as steady-state experimental data.
\r\n\r\nStatic input experiments for CO oxidation on supported Rh, reduced at 170\u00b0C, reveal oscillatory responses for some inlet conditions. Two adsorbed CO species, linear and dicarbonyl forms, are observed with the linearly adsorbed CO shown from step-response experiments to be more reactive than CO adsorbed in the dicarbonyl form. The oscillations seem to be driven by surface temperature fluctuations rather than by interconversion between the adsorbed CO species.
\r\n\r\nSteady-state and step-response experiments at 147\u00b0C are used to estimate and to bound parameters in two reaction models that were previously postulated for CO oxidation on supported Ag. Data from feedback-induced steady-state bifurcation experiments are reproduced well by both models but neither reaction model is able to reproduce closed-loop Hopf bifurcation data. Also, long-time-scale transients observed in some step-response experiments are not accurately simulated by either model. A new model is proposed for CO oxidation on Ag/Al\u2082O\u2083, which incorporates a slow reversible step that forms an adsorbed oxygen species that blocks reaction sites. This model is able to reproduce the long-time-scale dynamics and a variety of cycled feedstream experiments.
\r\n\r\nThe feedback-induced bifurcation method is also applied to the CO oxidation reaction on supported Rh. After reducing the Rh/Al\u2082O\u2083 catalyst at 500\u00b0C, only linearly adsorbed CO is observed. Measurements of the fractional coverage of CO and the gas-phase CO are used for feedback control. The closed-loop bifurcation data are used to discriminate between two reaction models for CO oxidation on supported Rh, which are determined from steady-state experiments. Higher order dynamics resulting from closed-loop operation are also observed. The usefulness of various types of experimental feedback-induced bifurcations, as applied to model development, is discussed.
\r\n\r\nFinally, the feedback-induced bifurcation method is used to generate basis oscillations that are subjected to forced periodic operation. This provides a process in which entrainment behavior can be systematically examined. Experimental and simulated entrainment responses are compared and are found to be in close agreement.
\r\n", "doi": "10.7907/pf3v-jt53", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:4451", "collection": "thesis", "collection_id": "4451", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11072007-140642", "type": "thesis", "title": "Mathematical Modeling of the Dynamics and Thermodynamics of Multicomponent Atmospheric Aerosols", "author": [ { "family_name": "Pilinis", "given_name": "Christodoulos", "clpid": "Pilinis-Christodoulos" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Lorenz", "given_name": "Jens", "clpid": "Lorenz-Jens" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Atmospheric aerosols consist of particles with sizes between 0.01 and 10\u00b5m. These particles, when occurring in urban areas, consist, in general, of aqueous solutions of sulfate, nitrate, ammonium, chloride, sodium and other ionic species, as well as of primary and secondary organics.
\r\n\r\nThis thesis attempts to describe the evolution and fate of atmospheric aerosol particles. The size-composition distribution of atmospheric aerosols is governed by a combination of kinetics and thermodynamics, which, because of their complexity, can be analyzed only with computer simulations. At first, a solution of the General Dynamic Equation in the case of small coagulation, using perturbation techniques, is developed.
\r\n\r\nIn subsequent work, a comprehensive size-sectionalized trajectory aerosol model was developed for simulating the evolution of a multicomponent aerosol size-composition distribution through homogeneous heteromolecular nucleation, condensational growth, coagulation and deposition. The model was employed along a trajectory from Anaheim to Rubidoux, California.
\r\n\r\nIn the process of analyzing this model it became apparent that a detailed treatment of the thermodynamics of the sodium/ sulfate/ nitrate/ ammonium/ chloride/ water system is very important in aerosol predictions. Thus, an equilibrium model for this system that takes into account differences in the composition among particles of different sizes was developed and tested.
\r\n\r\nFinally, the same theory was used in a Eulerian framework, thus producing a three-dimensional Eulerian Urban Gas-Aerosol Model, which was used to predict the aerosol concentration and size distribution throughout the Los Angeles Basin on August 30, 1982. Its prediction is compared with measured values and a statistical evaluation study is presented.
\r\n", "doi": "10.7907/t5w6-2r52", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:1632", "collection": "thesis", "collection_id": "1632", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05052006-140158", "primary_object_url": { "basename": "Rivera_de_1987.pdf", "content": "final", "filesize": 6189284, "license": "other", "mime_type": "application/pdf", "url": "/1632/1/Rivera_de_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Modeling Requirements for Process Control", "author": [ { "family_name": "Rivera", "given_name": "Daniel Eduardo", "clpid": "Rivera-Daniel-Eduardo" } ], "thesis_advisor": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" } ], "thesis_committee": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Doyle", "given_name": "John Comstock", "clpid": "Doyle-J-C" }, { "family_name": "Sideris", "given_name": "Athanasios", "clpid": "Sideris-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Modeling and control system design have traditionally been viewed as distinct, independent problems. Not all model characteristics, however, are relevant to the control system design problem. One can expect, then, that parsimonious, more effective controllers are possible if control considerations are incorporated in the modeling stage.
\r\n\r\nThe synergism of dynamic modeling and process control, as pertaining to the fields of low-order controller design, model reduction, and model identification, is investigated in this thesis. The guiding theoretical framework is the robust control paradigm using the Structured Singular Value, which addresses controller design in the presence of model uncertainty.
\r\n\r\nThe main contribution of this thesis is the development of a control-relevant model reduction methodology. The effectiveness of reduction is increased by incorporating the closed-loop performance/robustness specifications, plant uncertainties, and setpoint/disturbance characteristics explicitly as weights in the reduction procedure. The efficient computation of the control-relevant reduction problem is indicated and illustrated with examples taken from the control of a methanation reactor and a binary distillation column.
\r\n\r\nA low-order controller design methodology for single-input, single-output plants is also presented. The basis for this methodology is the combination of the control-relevant reduction problem with the Internal Model Control (IMC) design procedure. The relationship between low-order IMC controllers and classical feeback compensators is examined. It is shown that for many models common to the process industries, the controllers obtained from the low-order compensator design technique are of the PID type.
\r\n\r\nFinally, a model identification methodology is established using spectral time series analysis to obtain plant transfer function and uncertainty estimates directly from experiments. The control-relevant model reduction procedure can then be used to fit the \"full-order\" frequency response to a \"reduced-order\" parametric model. Model validation for control purposes is achieved by insuring that the robustness condition is satisfied.
\r\n", "doi": "10.7907/KS5Q-PJ57", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:1049", "collection": "thesis", "collection_id": "1049", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03212008-092922", "primary_object_url": { "basename": "Mandler_ja_1987.pdf", "content": "final", "filesize": 22500905, "license": "other", "mime_type": "application/pdf", "url": "/1049/1/Mandler_ja_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Robust Control System Design for a Fixed-Bed Catalytic Reactor", "author": [ { "family_name": "Mandler", "given_name": "Jorge Anibal", "clpid": "Mandler-Jorge-Anibal" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Doyle", "given_name": "John Comstock", "clpid": "Doyle-J-C" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The design of control systems in the face of model uncertainty is addressed. A methodology for the design of robust control schemes is outlined, which employs the Structured Singular Value as an analysis tool and Internal Model Control as the synthesis framework. This methodology is applied to the design of control systems for a fixed-bed, laboratory, catalytic methanation reactor. The design procedure allows a clear insight on the fundamental limits to closed-loop performance and provides controllers with explicit stability and performance guarantees for the case of plant-model mismatch.
\r\n\r\nThe overall controller design effort is initiated with a careful mathematical modeling of the system. The original nonlinear partial differential equations are converted through collocation techniques into a nonlinear ordinary-differential/algebraic equation system amenable to dynamic simulation. Interactive software is developed for the open- and closed-loop simulation of general nonlinear differential-algebraic systems, which provides an efficient means to simulate the reactor model. Linearization and control-relevant model reduction techniques are applied to arrive at models appropriate for the control studies.
\r\n\r\nBoth the single-input single-output and the multivariable case are addressed. Three different control configurations are investigated in the context of the single- pass operation of the reactor. In each case-study presented, the controller design procedure is divided into four steps: first, the definition of the control objectives, which not only leads to the selection of the appropriate control configuration but also determines the most adequate design techniques to employ; second, a nominal design step, in which the system-inherent limitations to the closed-loop performance are highlighted; third, a characterization of the uncertainty and the use of this information in the design of robust controllers; and, fourth, the evaluation of the designs through nonlinear simulations.
\r\n\r\nThe thesis describes the first application of structured singular value-based analysis techniques to a chemical reactor system and is in essence the first comprehensive study of the application of robust control to fixed-bed reactors. The power of the new mathematical theory for robust control system design is demonstrated. It is shown that the design of control systems for complex, distributed systems such as the methanation reactor can be addressed in a practical way, and low-order controllers be adequately obtained, which possess near-optimal characteristics when applied in a realistic environment of uncertainty and unavailability of measurements.
\r\n", "doi": "10.7907/czeb-7c12", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:4425", "collection": "thesis", "collection_id": "4425", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11062007-092509", "type": "thesis", "title": "Response and Failure of Fluid-Filled Tanks under Base Excitation", "author": [ { "family_name": "Natsiavas", "given_name": "Sotirios", "clpid": "Natsiavas-Sotirios" } ], "thesis_advisor": [ { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "thesis_committee": [ { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Babcock", "given_name": "Charles D.", "clpid": "Babcock-C-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "An analytical model is developed that leads to better understanding of the response of fluid-filled tanks whose bottom may separate from and lift off the foundation, during base excitation. First, the hydrodynamic problem is solved in closed form, for the most general motion of the structure. This eliminates the fluid response unknowns and therefore only the structural degrees-of-freedom need to be considered. Then, application of Hamilton's Principle in the structural domain sets up the system equations of motion. During this procedure, the uplifting behavior is modeled by an appropriate rotational spring, placed between the foundation and the bottom of the tank. Equivalent springs are also used for modeling the ground/structure interaction. Moreover, shell flexibility and liquid sloshing effects are also incorporated and investigated.
\r\n\r\nUsing this model, results are obtained and compared with experimental data. This comparison reveals some interesting effects of the base uplift on the system response. Ground flexibility is found to reduce the effective beam-type stiffness of the structure, but this reduction is much smaller than the substantial stiffness reduction induced by the possibility of uplifting. For the cases examined, the stiffness reduction due to the base uplift changes dramatically the dynamics of the system, which in turn alters the developed hydrodynamic loads, through the fluid/structure coupling process. Also, the shell flexibility effects - which can be important for the anchored tank case - are found to be negligible for an unanchored tank. Knowledge of the structural response leads to direct calculation of the hydrodynamic loads and consequently to prediction of failure. Buckling phenomena observed experimentally at the top and the bottom of scale model tanks are studied and explained.
\r\n", "doi": "10.7907/CNWT-V417", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:1036", "collection": "thesis", "collection_id": "1036", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03202008-105002", "type": "thesis", "title": "Studies of Concentrated Electrolyte Solutions Using the Electrodynamic Balance", "author": [ { "family_name": "Cohen", "given_name": "Mark Daniel", "clpid": "Cohen-Mark-Daniel" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "An electrodynamic balance has been used to measure the water activity as a function of solute concentration at 20 \u00b0C for eleven single-electrolyte aqueous solutions - NaCl, NaBr, KCl, KBr, NH4Cl, Na2SO4, (NH4)2SO4, CaCl2, MnCl2, MnSO4 and FeCl3 - and three mixed-electrolyte aqueous solutions - NaCl-KCl, NaCl-KBr, and NaCl-(NH4)2SO4. The measurements were performed by levitating single, charged, 20-micron diameter droplets of these solutions within the balance and measuring the mass of the particles as a function of the surrounding relative humidity. The deliquescence behavior of the particles was also observed.
\r\n\r\nHeterogeneous nucleation was inhibited due to the absence of container walls and because the small droplets were less likely than a bulk sample to contain foreign particles. Thus, this technique allowed the thermodynamics of highly concentrated solutions to be studied. For most of the solutions, water activity measurements were made to higher solute concentrations than have previously been reported. At low concentrations, the results were consistent with previously published data. Nucleation theory was used to estimate the surface excess free energy and critical nucleus size from the measured supersaturation at which nucleation occurred.
\r\n\r\nFor the single-electrolyte solutions, the dependence of the solute activity coefficient on concentration was calculated, and the features of this dependence are discussed in relationship to ionic hydration and association. Several semi-empirical electrolyte solution models were tested against the data, and it was found that salt-specific model parameters estimated from low concentration data could not be reliably used to predict the solution behavior at high concentrations. However, with estimated parameters based on the full range of the data, the models were able to represent the experimental data for single-electrolyte solutions to within the uncertainty in the measurements.
\r\n\r\nThree models of mixed-electrolyte solutions \u2014 the Zdanovskii-Stokes-Robinson, Reilly-Wood-Robinson and Pitzer methods \u2014 agreed well with the experimental data for the NaCl-KCl and NaCl-KBr systems over the range of concentration that the models could be applied. The mixing rules' predictions were consistent with the experimental observations for the NaCl-(NH4)2SO4 particles assuming a small amount of water was retained in the dry state.
", "doi": "10.7907/5ZEY-MH91", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:829", "collection": "thesis", "collection_id": "829", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03012008-135126", "primary_object_url": { "basename": "Lee_t_1987.pdf", "content": "final", "filesize": 5834334, "license": "other", "mime_type": "application/pdf", "url": "/829/1/Lee_t_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Estimation of Petroleum Reservoir Properties", "author": [ { "family_name": "Lee", "given_name": "Tai-yong", "clpid": "Lee-Tai-yong" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Chen", "given_name": "Wen H.", "clpid": "Chen-Wen-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Numerical algorithms are developed to estimate petroleum reservoir properties such as absolute permeability, porosity, and relative permeabilities based on the noisy pressure and flow data. Regularization and spline approximation of spatially varying parameters are employed to convert the ill-posed nature of the problem to a well-posed one. A stabilizing functional with gradient operator is used to measure the non-smoothness of the parameter estimates. The number of spline coefficients along each spatial direction is chosen to be as much as the number of meshes for the reservoir PDE's. New history matching algorithms are developed that determine the regularization parameter during the computation without requiring a priori information and improve the parameter estimates stepwise. A partial conjugate gradient method is employed for the estimation of a single set of parameters, and the steepest descent algorithm is used for the simultaneous estimation of absolute and relative permeabilities. A rough parametric sensitivity analysis is carried out for the simultaneous estimation to improve the convergence. Numerical tests are carried out to estimate the parameters in single- and two-phase reservoirs for the different choices of the stabilizing functionals, the regularization parameters, and the degrees of spline approximation; and the effects of the observation error, the observation time, and the configuration of the observation points are investigated. The results show that the new algorithms generate better parameter estimates over the various possible choices of the estimation conditions.
", "doi": "10.7907/gs7z-gy70", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:2587", "collection": "thesis", "collection_id": "2587", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06142006-104731", "type": "thesis", "title": "Studies on Robust Control of Distillation Columns", "author": [ { "family_name": "Skogestad", "given_name": "Sigurd", "clpid": "Skogestad-Sigurd" } ], "thesis_advisor": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" } ], "thesis_committee": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Doyle", "given_name": "John Comstock", "clpid": "Doyle-J-C" }, { "family_name": "Sideris", "given_name": "Athanasios", "clpid": "Sideris-A" }, { "family_name": "Stephanopoulos", "given_name": "Gregory N.", "clpid": "Stephanopoulos-G-N" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Distillation is undoubtedly the most important unit operation in chemical engineering. During design a significant effort is normally put into steady-state optimization of the column with respect to its size, feed location and reflux ratio. However, operating the column close to this optimal point requires reasonably tight control of the product compositions. This is usually not achieved in industrial practice due to stability problems. Improved strategies for distillation control offer a viable means for significant economic savings as compared to the existing ad hoc techniques. This thesis addresses robust control of distillation columns in the face of model-plant mismatch caused by model uncertainty, nonlinearity and changes in operating conditions. The robust control paradigm, introduced by Doyle and coworkers, is used as the basis for controller design and analysis. An important tool is the Structured Singular Value (SSV) which enables the evaluation of a plant's achievable control performance. This provides a consistent basis for comparing controllers and design alternatives. Achievable performance is also related to other commonly used measures such as the RGA and the condition number.
\r\n\r\nPhysical insight is used to derive low-order column models which address the issues most important for feedback control. It is shown that the dynamic behavior can be explained in terms of the fundamental difference between external and internal flows. This difference manifests itself both at steady-state and in the dynamic response. Furthermore, the initial response, which is of principal importance for feedback control, is affected much less by changes in the operating conditions than is the steady-state response. The initial response is even less markedly affected when logarithmic compositions are used.
\r\n\r\nAn important issue in distillation control is which two of the possible five manipulated inputs should be selected for composition control; each configuration may yield entirely different control performance. Issues which must be addressed include model uncertainty and dynamic response as well as rejection of flow disturbances by the level loops.
\r\n\r\nFinally, a design method for robust decentralized controllers, which generalizes the SSV-interaction measure of Grosdidier and Morari, is introduced. Each loop is designed independently such that robust performance of the overall system is guaranteed.
", "doi": "10.7907/WS2X-Z786", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:885", "collection": "thesis", "collection_id": "885", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03052008-111804", "primary_object_url": { "basename": "Grader_gs_1987.pdf", "content": "final", "filesize": 7213605, "license": "other", "mime_type": "application/pdf", "url": "/885/1/Grader_gs_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Fourier Transform Infrared Spectroscopy of a Single Aerosol Particle", "author": [ { "family_name": "Sageev Grader", "given_name": "Gideon", "clpid": "Sageev-Grader-Gideon" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Baldeschwieler", "given_name": "John D.", "clpid": "Baldeschwieler-J-D" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Throughout this thesis, the phenomenon of radiation-induced particle size change is studied both on a theoretical as well as experimental level. The thrust of this study is aimed at using the size changes due to heat absorption to develop a technique for obtaining the particle chemical composition.
\r\n\r\nThe experiments here involve charged particles, generated with an impulse jet, and trapped by the electric field of an electrodynamic balance. The particles under study are all aqueous solutions of non-volatile salts, where upon heating a partial evaporation of water occurs. The evaporation and subsequent condensation processes are modeled in both the continuum and the transition regimes. The models developed are tested and the agreement between theory and experimental results is demonstrated. The models are also used to extract the values of the water, thermal, and mass accommodation coefficients from the data. The results for the thermal accommodation show that its value is near unity, however the corresponding results for the mass accommodation are not conclusive.
\r\n\r\nA method is developed for obtaining the molecular composition of a single suspended microparticle by Fourier transform infrared spectroscopy. The particle is irradiated simultaneously by the infrared output from a Michelson interferometer and the visible light from a dye laser. The laser is tuned to an edge of an optical resonance of the particle while the IR beam is chopped. Through evaporation and condensation the chopped IR beam causes a size modulation of the droplet, which in turn induces a fluctuation in the laser light scattered from the particle. The scattered light is detected at 90\u00b0 with a photomultiplier, and the amplitude of the light fluctuation is measured with a lock-in amplifier. The lock-in signal is then inverted by a discrete fast Fourier transform routine (FFT), to yield the particle absorption spectrum. Spectra of (NH4)2SO4 droplets at different solute concentrations are presented.
\r\n", "doi": "10.7907/de8x-sp79", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:1633", "collection": "thesis", "collection_id": "1633", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05052006-140832", "type": "thesis", "title": "A Methodology for the Synthesis of Robust Control Systems for Multivariable Sampled-Data Processes", "author": [ { "family_name": "Zafiriou", "given_name": "Evanghelos", "clpid": "Zafiriou-Evanghelos" } ], "thesis_advisor": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" } ], "thesis_committee": [ { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" }, { "family_name": "Caughey", "given_name": "Thomas Kirk", "clpid": "Caughey-T-K" }, { "family_name": "Doyle", "given_name": "John Comstock", "clpid": "Doyle-J-C" }, { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The problem of the synthesis of multivariable controllers which are robust with respect to model-plant mismatch is addressed. A two-step design procedure based on the Internal Model Control (IMC) structure is used. In the first step the IMC controller is designed assuming no modeling error, and in the second step the IMC filter is designed to preserve the closed-loop characteristics in spite of model-plant mismatch.
\r\n\r\nTwo alternatives are provided for the first step. One of them allows the designer to satisfy structural performance specifications, in terms of the structure of the closed-loop interactions, their magnitude and duration. The closed-loop transfer function matrix is directly designed. The method requires only standard linear algebra operations and includes the construction of the IMC or the feedback controller in state-space. The second approach involves the minimization of the appropriately weighted H2-norm of the sensitivity transfer function matrix, that relates the errors to the external inputs (setpoints or disturbances). A method is given for the meaningful selection of a full matrix weight so that the H2-error is minimized for a set of external input directions and their linear combinations. The procedure is extended to open-loop unstable systems. In both approaches, special care is taken to avoid intersample rippling.
\r\n\r\nThe design of the filter in the second step is formulated as an optimization problem over the filter parameters. The objective function is constructed by using the Structured Singular Value theory so that the maximum singular value of the sensitivity transfer function remains bounded in spite of modeling error. The selection of the frequency bound is based on the properties of the design that was obtained in the first step. Analytic gradient expressions have been developed for the objective function. The optimization problem is an unconstrained one, solved with standard gradient search techniques. An iterative method for the selection of the appropriate sampling time is proposed, which explicitly takes into account model uncertainty information and performance specifications.
\r\n", "doi": "10.7907/m08p-9102", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:1626", "collection": "thesis", "collection_id": "1626", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05052006-082025", "primary_object_url": { "basename": "Edelstein_s_1987.pdf", "content": "final", "filesize": 5571003, "license": "other", "mime_type": "application/pdf", "url": "/1626/1/Edelstein_s_1987.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Adsorption of Sulphur Dioxide and Reduction of Sulphate on Alumina and Alkali-Alumina at High Temperatures", "author": [ { "family_name": "Edelstein", "given_name": "Sergio", "clpid": "Edelstein-Sergio" } ], "thesis_advisor": [ { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" } ], "thesis_committee": [ { "family_name": "Gavalas", "given_name": "George R.", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "clpid": "Seinfeld-J-H" }, { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Morari", "given_name": "Manfred", "clpid": "Morari-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Several interrelated problems in connection with the treatment of sulfur dioxide at temperatures between 700 and 800\u00b0C were studied. The interaction of SO2 with Al2O3 was studied experimentally using B.E.T., thermogravimetry and temperature-programmed desorption. Adsorption takes place through a wide range of binding energies, with some SO2 adsorbing irreversibly at temperatures below 800\u00b0C. The amount adsorbed depends on the surface history and thermal treatment. An adsorption isotherm based on a bimodal energy distribution provides an adequate description of the equilibrium process.
\r\n\r\nThe chemical composition, sulfation and regeneration of an alkali-alumina sorbent for sulfur dioxide were studied using thermogravimetry, gas chromatography, and X-ray photoelectron spectroscopy. The active sorbent consists of a thin layer of sodium and lithium aluminates supported on alumina. The rate of sulfation is proportional to the SO2 concentration in the gas, up to [SO2] \u2248 5000 ppm. The activation energy of the sulfation is E = 21.6 kcal/mole. The sulfated sorbent was regenerated by reduction with CO at 700-800\u00b0C. Sulfur removal from the sorbent and distribution of gaseous products were measured at different alkali loadings, temperatures and CO concentrations. The reduction takes place in two consecutive stages through a complex reaction network in which the alumina support plays a decisive role, both as a reactant and as a catalyst. A simplified reaction network is used as a basis for a kinetic model that provides an adequate description of the reduction process at moderate sorbent loadings.
", "doi": "10.7907/4CFM-WQ54", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:1119", "collection": "thesis", "collection_id": "1119", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03252008-092905", "primary_object_url": { "basename": "Gray_ha_1986.pdf", "content": "final", "filesize": 10658832, "license": "other", "mime_type": "application/pdf", "url": "/1119/1/Gray_ha_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Control of Atmospheric Fine Primary Carbon Particle Concentrations", "author": [ { "family_name": "Gray", "given_name": "Harry Andrew", "clpid": "Gray-Harry-Andrew" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Franklin", "given_name": "Joel N.", "clpid": "Franklin-J-N" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The adverse health effects and urban visibility degradation associated with atmospheric carbon particle concentrations suggest that control of this class of air pollutants is desirable, especially in the event of an increase in the usage of diesel vehicles. In this study, procedures for the engineering design of fine carbonaceous particulate matter abatement strategies have been developed and tested in the Los Angeles area. Carbon particle abatement strategies are evaluated based on the results of an emissions to air quality model, the performance of which is verified by comparison to measurements of ambient aerosol concentrations taken in the South Coast Air Basin during 1982.
\r\n\r\nAs a result of this research, the long\u2014term average behavior of fine aerosol carbon concentrations has been characterized in the Los Angeles area for the first time. The highest concentrations of fine particulate total carbon were observed in areas of heavy traffic density. The annual average fine total carbon concentration at downtown Los Angeles was 12.2 \u00b5g m-3 during 1982, which constituted 37% of the fine aerosol (dp < 2.1 \u00b5m) mass collected at that location. Aerosol carbon concentrations were observed to decrease with distance inland from downtown Los Angeles. The 1982 annual average fine total carbon concentration at Rubidoux, which is about 80 km east of Los Angeles, was only 8.2 \u00b5g m-3. There is a pronounced winter peak and summer minimum in carbonaceous aerosol concentrations in the western portion of the air basin. The monthly average fine total carbon concentration at downtown Los Angeles reached a high of 22.3 \u00b5g m-3 during December 1982, and dropped to 7.4 \u00b5g m-3 during June 1982. At eastern locations in the air basin, the seasonal trend becomes less significant, with monthly average fine total carbon concentrations at Rubidoux observed to be between 6.4 and 10.8 \u00b5g m-3 during all months of 1982.
\r\n\r\nElemental carbon in the atmosphere is inert and is due solely to direct (primary) aerosol emissions from sources, while organic carbon could be directly emitted as primary aerosol or could be formed in part from condensation of the low vapor pressure products of atmospheric chemical reactions (secondary formation). Examination of the spatial and temporal trends of the ratio of fine total carbon to fine elemental carbon concentration leads to the conclusion that secondary organic carbon aerosol formed in the atmosphere from hydrocarbon precursors was not the overwhelming contributor to overall long\u2014term average total carbon levels in the Los Angeles area during the year 1982. At downwind locations, such as Azusa or Rubidoux, it was found that, at most, between 16% and 22% of the annual average total carbon concentration (or 27% to 38% of the organic carbon) may be due to secondary aerosol formation in excess of that found at Lennox (a near\u2014coastal site next to a heavily travelled freeway source of primary aerosol). Comparison of fine elemental and organic carbon particle concentrations against the ratio of those two aerosol species found in basin\u2014wide source emissions further indicates that, over long averaging times during 1982, primary aerosol carbon particle emissions are responsible for the majority of atmospheric carbon particle concentrations.
\r\n\r\nThe particulate air quality data collected during 1982 were used to verify the performance of a mathematical model for long-term average air quality. The Lagrangian particle-in-cell air quality model previously developed by Cass (1977, 1981) was improved to handle near-source dispersion from ground level sources. The model was tested against emissions, elemental carbon air quality, and meteorological data for 1982 in the Los Angeles area. It was found that the model adequately predicts the long-term average concentration of this primary pollutant. The predictions and observations of monthly average elemental carbon particle concentrations have a positive correlation coefficient of 0.78. The model also determines the source classes responsible for fine carbon particle air quality. Many source types, including highway vehicles, charcoal broilers, and fireplaces contribute to primary total carbon particle concentrations, while elemental carbon concentrations are due mostly to emissions from diesel engines.
\r\n\r\nThe source class contributions computed by the air quality model were used to determine the optimal emission control strategy for attaining any desired level of improved carbon particle air quality. Linear programming techniques were employed to solve for the least costly set of emission control measures which would enable an air quality goal to be met. Solutions indicate that application of a few control measures, aimed almost entirely at diesel engines, will reduce the basin\u2014wide maximum annual average fine elemental carbon concentration approximately by half at an annual cost of about $69 million. The maximum annual average fine primary total carbon concentration may be reduced by about 35% at a cost of $102 million per year. A control program for visibility improvement would preferentially require the reduction of atmospheric fine elemental carbon particle concentrations, whereas a program designed to control fine aerosol mass would benefit from total carbon particle concentration reductions. It was determined that a control strategy that is optimal for total carbon control may be near\u2014optimal for elemental carbon control. However, an emissions control strategy designed to optimize for elemental carbon control may produce peak total carbon concentrations that exceed those which would result from a control strategy optimized for total carbon by as much as 8%.
\r\n\r\nIn summary, it has been demonstrated that the air quality model is useful both in predicting long\u2014term average carbon particle air quality and in determining the sources responsible for that air quality outcome. It was found that emissions from diesel engines were responsible for a large portion of the atmospheric fine carbon particle concentrations in the Los Angeles area during 1982. Control of emissions from diesel engines is therefore important, and it was determined that the least costly set of emission control measures for reducing carbon particle concentrations includes many diesel engine emission controls.
", "doi": "10.7907/p3dp-1v47", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:4541", "collection": "thesis", "collection_id": "4541", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11132007-105408", "primary_object_url": { "basename": "Hookham_pa_1986.pdf", "content": "final", "filesize": 3391092, "license": "other", "mime_type": "application/pdf", "url": "/4541/1/Hookham_pa_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Concentration and Velocity Measurements in Suspensions Flowing through a Rectangular Channel", "author": [ { "family_name": "Hookham", "given_name": "Philip Alan", "clpid": "Hookham-Philip-Alan" } ], "thesis_advisor": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" } ], "thesis_committee": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" }, { "family_name": "Brennen", "given_name": "Christopher E.", "clpid": "Brennen-C-E" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Corcoran", "given_name": "William Harrison", "clpid": "Corcoran-W-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A method to measure particle concentrations in dilute to moderately concentrated transparent liquid-solid suspensions was developed. The method uses a dual-beam laser-Doppler anemometer system. Particle concentrations were determined by counting the number of signals from fluorescently-dyed tracer particles per unit time. Using this method, both the velocities and concentrations of suspended particles were obtained.
\r\n\r\nVelocity and concentration measurements were made in suspensions of neutrally-buoyant polystyrene-divinylbenzene spheres 27, 50, and 70 \u00b5m in diameter flowing in a rectangular channel with 800 \u00b5m spacing between walls. Measurements were made in the central plane of the flow channel, thus approximating two-dimensional flow. Dilute-suspension (particle volume fraction \u03a6m = 0.001) experiments were performed both at Reynolds numbers that were low enough so that inertial effects were unimportant (particle Reynolds number Rep < 10-3), and Reynolds numbers at which inertial effects were significant (Rep = 10-3-10-1). Concentrated-suspension (\u03a6m = 0.02-0.25) experiments were done at low Rep only.
\r\n\r\nFor the dilute suspensions at low Re, small peaks in the concentration distributions were found near the flow channel walls, which were attributed to an entrance effect. At higher Re, lateral migration of particles due to inertia was observed. The spheres migrated toward a lateral equilibrium position about 0.6 times the distance from the flow channel centerline to the walls, as demonstrated previously by others. The measured concentration profiles were compared to a previously published theory for the lateral migration of a single sphere, and it was found that the peaks near the equilibrium positions in the measured concentration distributions were somewhat broader than those predicted by the theory, presumably due to particle-particle interactions.
\r\n\r\nNon-uniform concentration profiles were observed for the concentrated suspensions. The concentration profiles became somewhat peaked in the center of the channel as \u03a6m and/or sphere diameter increased, particularly for the 50 and 70 \u00b5m sphere suspensions, and for these suspensions the velocity profiles were blunted for \u03a6m \u2265 0.10. A model velocity profile calculation indicated that the shape of the concentration profiles could satisfactorily account for the shape of the velocity profiles, except possibly for the suspensions of 70 \u00b5m spheres.
\r\n", "doi": "10.7907/hv1g-s887", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:4541", "collection": "thesis", "collection_id": "4541", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11132007-105408", "primary_object_url": { "basename": "Hookham_pa_1986.pdf", "content": "final", "filesize": 3391092, "license": "other", "mime_type": "application/pdf", "url": "/4541/1/Hookham_pa_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Concentration and Velocity Measurements in Suspensions Flowing through a Rectangular Channel", "author": [ { "family_name": "Hookham", "given_name": "Philip Alan", "clpid": "Hookham-Philip-Alan" } ], "thesis_advisor": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" } ], "thesis_committee": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" }, { "family_name": "Brennen", "given_name": "Christopher E.", "clpid": "Brennen-C-E" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Corcoran", "given_name": "William Harrison", "clpid": "Corcoran-W-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A method to measure particle concentrations in dilute to moderately concentrated transparent liquid-solid suspensions was developed. The method uses a dual-beam laser-Doppler anemometer system. Particle concentrations were determined by counting the number of signals from fluorescently-dyed tracer particles per unit time. Using this method, both the velocities and concentrations of suspended particles were obtained.
\r\n\r\nVelocity and concentration measurements were made in suspensions of neutrally-buoyant polystyrene-divinylbenzene spheres 27, 50, and 70 \u00b5m in diameter flowing in a rectangular channel with 800 \u00b5m spacing between walls. Measurements were made in the central plane of the flow channel, thus approximating two-dimensional flow. Dilute-suspension (particle volume fraction \u03a6m = 0.001) experiments were performed both at Reynolds numbers that were low enough so that inertial effects were unimportant (particle Reynolds number Rep < 10-3), and Reynolds numbers at which inertial effects were significant (Rep = 10-3-10-1). Concentrated-suspension (\u03a6m = 0.02-0.25) experiments were done at low Rep only.
\r\n\r\nFor the dilute suspensions at low Re, small peaks in the concentration distributions were found near the flow channel walls, which were attributed to an entrance effect. At higher Re, lateral migration of particles due to inertia was observed. The spheres migrated toward a lateral equilibrium position about 0.6 times the distance from the flow channel centerline to the walls, as demonstrated previously by others. The measured concentration profiles were compared to a previously published theory for the lateral migration of a single sphere, and it was found that the peaks near the equilibrium positions in the measured concentration distributions were somewhat broader than those predicted by the theory, presumably due to particle-particle interactions.
\r\n\r\nNon-uniform concentration profiles were observed for the concentrated suspensions. The concentration profiles became somewhat peaked in the center of the channel as \u03a6m and/or sphere diameter increased, particularly for the 50 and 70 \u00b5m sphere suspensions, and for these suspensions the velocity profiles were blunted for \u03a6m \u2265 0.10. A model velocity profile calculation indicated that the shape of the concentration profiles could satisfactorily account for the shape of the velocity profiles, except possibly for the suspensions of 70 \u00b5m spheres.
\r\n", "doi": "10.7907/hv1g-s887", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:436", "collection": "thesis", "collection_id": "436", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02012007-092322", "primary_object_url": { "basename": "Georgopoulos-PG_1986.pdf", "content": "final", "filesize": 22931382, "license": "other", "mime_type": "application/pdf", "url": "/436/1/Georgopoulos-PG_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Mathematical Studies of Photochemical Air Pollution", "author": [ { "family_name": "Georgopoulos", "given_name": "Panagiotis Gerasimou", "clpid": "Georgopoulos-Panagiotis-Gerasimou" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "List", "given_name": "E. John", "clpid": "List-E-J" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "In Part I a new, comprehensive model for a chemically reacting plume, is presented, that accounts for the effects of incomplete turbulent macro- and micro- mixing on chemical reactions between plume and ambient constituents. This \"Turbulent Reacting Plume Model\" (TRPM) is modular in nature, allowing for the use of different levels of approximation of the phenomena involved. The core of the model consists of the evolution equations for reaction progress variables appropriate for evolving, spatially varying systems (\"local phenomenal extent of reaction\"). These equations estimate the interaction of mixing and chemical reaction and require input parameters characterizing internal plume behavior, such as relative dispersion and fine scale plume segregation. The model addresses deficiencies in previous reactive plume models. Calculations performed with the TRPM are compared with the experimental data of P.J.H. Builtjes for the reaction between NO in a point source plume and ambient O3, taking place in a wind tunnel simulating a neutral atmospheric boundary layer. The comparison shows the TRPM capable of quantitatively predicting the retardation imposed on the evolution of nonlinear plume chemistry by incomplete mixing. Part IA (Chapters 1 to 3) contains a detailed description of the TRPM structure and comparisons of calculations with measurements, as well as a literature survey of reactive plume models. Part IB (Chapters 4 to 7) contains studies on the turbulent dispersion and reaction phenomena and plume dynamics, thus exposing in detail the underlying concepts and methods relevant to turbulent reactive plume modeling. New formulations for describing in-plume phenomena, such as the \"Localized Production of Fluctuations Model\" for the calculation of the plume concentration variance are included here.
\r\n\r\nPart II (Chapter 8) presents a collection of distribution-based statistical methods that are appropriate for characterizing extreme events in air pollution studies. Applications to the evaluation of air quality standards, formulation of rollback calculations, and to the use of plume models are included here.
", "doi": "10.7907/71dn-x264", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:1104", "collection": "thesis", "collection_id": "1104", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03242008-134119", "primary_object_url": { "basename": "Conklin_mh_1986.pdf", "content": "final", "filesize": 7032584, "license": "other", "mime_type": "application/pdf", "url": "/1104/1/Conklin_mh_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Thermodynamics, Kinetics and Mechanisms of the Reactions of S(IV) with Cu(II) and Fe(III)", "author": [ { "family_name": "Conklin", "given_name": "Martha Harriet", "clpid": "Conklin-Martha-Harriet" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Chan", "given_name": "Sunney I.", "orcid": "0000-0002-5348-2723", "clpid": "Chan-S-I" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Spectrosopic methods are used to determine the stability constant for the formation of CuSO3, K = 1.8 \u00b1 0.6 x 104 M-1 for \u00b5 = 0.4 M. Infrared and Raman measurements indicate that sulfite binds to the metal through both sulfur and oxygen. These results are compared to those of other first-row transition metal-sulfite complexes.
\r\n\r\nThe reduction of Cu(II) is shown to proceed via (Cu(II))2SO32+ and CuSO3CuOH+ intermediates. Copper(I), SO42- and a mixed valence compound Cu||SO3Cu2|SO3\u20222H2O are determined to be the principal products. The rate law is consistent with consecutive first-order reactions. Results are interpreted in terms of the initial formation of an inner-sphere complex which is followed by a rate-limiting electron transfer step. Previously accepted mechanisms for the trace metal catalysis of the autoxidation of SO32- are discussed in light of these results.
\r\n\r\nA conditional stability constant for the formation of a Fe(III)-S(IV) complex at \u00b5 = 0.4 M and pH 2.1 was determined spectroscopically. Raman measurements indicate that sulfite binds to the metal through oxygen. EPR experiments show that the reduction of Fe(III) to Fe(II) by S(IV) is a slow reaction at pH 2 (\u03c41/2 \u2243 8 min). Various pathways for the formation of the Fe(III)-S(IV) species are examined to determine the most probable equilibrium species. Results are interpreted by comparing the stability and bonding of Fe(III)-S(IV) species with other Fe(III) complexes.
\r\n\r\nThe rates of these internal redox reactions are too slow for this reaction to be important in the atmospheric autoxidation of S(IV), instead ternary metal-oxygen-sulfito complexes are proposed as the active catalytic species in aqueous atmospheric systems. Calculations based on the equilibrium constants obtained in this study indicate that metal-S(IV) complexes may be important equilibrium species in the absence of \u03b1-hydroxyalkylsulfonates. The catalytic autoxidation of SO2 in aqueous systems appears to proceed via the formation of metal-sulfite complexes as a prelude to electron-transfer.
\r\n", "doi": "10.7907/83k6-ex73", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:1104", "collection": "thesis", "collection_id": "1104", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03242008-134119", "primary_object_url": { "basename": "Conklin_mh_1986.pdf", "content": "final", "filesize": 7032584, "license": "other", "mime_type": "application/pdf", "url": "/1104/1/Conklin_mh_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Thermodynamics, Kinetics and Mechanisms of the Reactions of S(IV) with Cu(II) and Fe(III)", "author": [ { "family_name": "Conklin", "given_name": "Martha Harriet", "clpid": "Conklin-Martha-Harriet" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Chan", "given_name": "Sunney I.", "orcid": "0000-0002-5348-2723", "clpid": "Chan-S-I" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Spectrosopic methods are used to determine the stability constant for the formation of CuSO3, K = 1.8 \u00b1 0.6 x 104 M-1 for \u00b5 = 0.4 M. Infrared and Raman measurements indicate that sulfite binds to the metal through both sulfur and oxygen. These results are compared to those of other first-row transition metal-sulfite complexes.
\r\n\r\nThe reduction of Cu(II) is shown to proceed via (Cu(II))2SO32+ and CuSO3CuOH+ intermediates. Copper(I), SO42- and a mixed valence compound Cu||SO3Cu2|SO3\u20222H2O are determined to be the principal products. The rate law is consistent with consecutive first-order reactions. Results are interpreted in terms of the initial formation of an inner-sphere complex which is followed by a rate-limiting electron transfer step. Previously accepted mechanisms for the trace metal catalysis of the autoxidation of SO32- are discussed in light of these results.
\r\n\r\nA conditional stability constant for the formation of a Fe(III)-S(IV) complex at \u00b5 = 0.4 M and pH 2.1 was determined spectroscopically. Raman measurements indicate that sulfite binds to the metal through oxygen. EPR experiments show that the reduction of Fe(III) to Fe(II) by S(IV) is a slow reaction at pH 2 (\u03c41/2 \u2243 8 min). Various pathways for the formation of the Fe(III)-S(IV) species are examined to determine the most probable equilibrium species. Results are interpreted by comparing the stability and bonding of Fe(III)-S(IV) species with other Fe(III) complexes.
\r\n\r\nThe rates of these internal redox reactions are too slow for this reaction to be important in the atmospheric autoxidation of S(IV), instead ternary metal-oxygen-sulfito complexes are proposed as the active catalytic species in aqueous atmospheric systems. Calculations based on the equilibrium constants obtained in this study indicate that metal-S(IV) complexes may be important equilibrium species in the absence of \u03b1-hydroxyalkylsulfonates. The catalytic autoxidation of SO2 in aqueous systems appears to proceed via the formation of metal-sulfite complexes as a prelude to electron-transfer.
\r\n", "doi": "10.7907/83k6-ex73", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:1119", "collection": "thesis", "collection_id": "1119", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03252008-092905", "primary_object_url": { "basename": "Gray_ha_1986.pdf", "content": "final", "filesize": 10658832, "license": "other", "mime_type": "application/pdf", "url": "/1119/1/Gray_ha_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Control of Atmospheric Fine Primary Carbon Particle Concentrations", "author": [ { "family_name": "Gray", "given_name": "Harry Andrew", "clpid": "Gray-Harry-Andrew" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Franklin", "given_name": "Joel N.", "clpid": "Franklin-J-N" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The adverse health effects and urban visibility degradation associated with atmospheric carbon particle concentrations suggest that control of this class of air pollutants is desirable, especially in the event of an increase in the usage of diesel vehicles. In this study, procedures for the engineering design of fine carbonaceous particulate matter abatement strategies have been developed and tested in the Los Angeles area. Carbon particle abatement strategies are evaluated based on the results of an emissions to air quality model, the performance of which is verified by comparison to measurements of ambient aerosol concentrations taken in the South Coast Air Basin during 1982.
\r\n\r\nAs a result of this research, the long\u2014term average behavior of fine aerosol carbon concentrations has been characterized in the Los Angeles area for the first time. The highest concentrations of fine particulate total carbon were observed in areas of heavy traffic density. The annual average fine total carbon concentration at downtown Los Angeles was 12.2 \u00b5g m-3 during 1982, which constituted 37% of the fine aerosol (dp < 2.1 \u00b5m) mass collected at that location. Aerosol carbon concentrations were observed to decrease with distance inland from downtown Los Angeles. The 1982 annual average fine total carbon concentration at Rubidoux, which is about 80 km east of Los Angeles, was only 8.2 \u00b5g m-3. There is a pronounced winter peak and summer minimum in carbonaceous aerosol concentrations in the western portion of the air basin. The monthly average fine total carbon concentration at downtown Los Angeles reached a high of 22.3 \u00b5g m-3 during December 1982, and dropped to 7.4 \u00b5g m-3 during June 1982. At eastern locations in the air basin, the seasonal trend becomes less significant, with monthly average fine total carbon concentrations at Rubidoux observed to be between 6.4 and 10.8 \u00b5g m-3 during all months of 1982.
\r\n\r\nElemental carbon in the atmosphere is inert and is due solely to direct (primary) aerosol emissions from sources, while organic carbon could be directly emitted as primary aerosol or could be formed in part from condensation of the low vapor pressure products of atmospheric chemical reactions (secondary formation). Examination of the spatial and temporal trends of the ratio of fine total carbon to fine elemental carbon concentration leads to the conclusion that secondary organic carbon aerosol formed in the atmosphere from hydrocarbon precursors was not the overwhelming contributor to overall long\u2014term average total carbon levels in the Los Angeles area during the year 1982. At downwind locations, such as Azusa or Rubidoux, it was found that, at most, between 16% and 22% of the annual average total carbon concentration (or 27% to 38% of the organic carbon) may be due to secondary aerosol formation in excess of that found at Lennox (a near\u2014coastal site next to a heavily travelled freeway source of primary aerosol). Comparison of fine elemental and organic carbon particle concentrations against the ratio of those two aerosol species found in basin\u2014wide source emissions further indicates that, over long averaging times during 1982, primary aerosol carbon particle emissions are responsible for the majority of atmospheric carbon particle concentrations.
\r\n\r\nThe particulate air quality data collected during 1982 were used to verify the performance of a mathematical model for long-term average air quality. The Lagrangian particle-in-cell air quality model previously developed by Cass (1977, 1981) was improved to handle near-source dispersion from ground level sources. The model was tested against emissions, elemental carbon air quality, and meteorological data for 1982 in the Los Angeles area. It was found that the model adequately predicts the long-term average concentration of this primary pollutant. The predictions and observations of monthly average elemental carbon particle concentrations have a positive correlation coefficient of 0.78. The model also determines the source classes responsible for fine carbon particle air quality. Many source types, including highway vehicles, charcoal broilers, and fireplaces contribute to primary total carbon particle concentrations, while elemental carbon concentrations are due mostly to emissions from diesel engines.
\r\n\r\nThe source class contributions computed by the air quality model were used to determine the optimal emission control strategy for attaining any desired level of improved carbon particle air quality. Linear programming techniques were employed to solve for the least costly set of emission control measures which would enable an air quality goal to be met. Solutions indicate that application of a few control measures, aimed almost entirely at diesel engines, will reduce the basin\u2014wide maximum annual average fine elemental carbon concentration approximately by half at an annual cost of about $69 million. The maximum annual average fine primary total carbon concentration may be reduced by about 35% at a cost of $102 million per year. A control program for visibility improvement would preferentially require the reduction of atmospheric fine elemental carbon particle concentrations, whereas a program designed to control fine aerosol mass would benefit from total carbon particle concentration reductions. It was determined that a control strategy that is optimal for total carbon control may be near\u2014optimal for elemental carbon control. However, an emissions control strategy designed to optimize for elemental carbon control may produce peak total carbon concentrations that exceed those which would result from a control strategy optimized for total carbon by as much as 8%.
\r\n\r\nIn summary, it has been demonstrated that the air quality model is useful both in predicting long\u2014term average carbon particle air quality and in determining the sources responsible for that air quality outcome. It was found that emissions from diesel engines were responsible for a large portion of the atmospheric fine carbon particle concentrations in the Los Angeles area during 1982. Control of emissions from diesel engines is therefore important, and it was determined that the least costly set of emission control measures for reducing carbon particle concentrations includes many diesel engine emission controls.
", "doi": "10.7907/p3dp-1v47", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:1048", "collection": "thesis", "collection_id": "1048", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03212008-085926", "primary_object_url": { "basename": "Warren_dr_1986.pdf", "content": "final", "filesize": 17901937, "license": "other", "mime_type": "application/pdf", "url": "/1048/1/Warren_dr_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Nucleation and Growth of Aerosols", "author": [ { "family_name": "Warren", "given_name": "Dale Ross", "clpid": "Warren-Dale-Ross" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Grosjean", "given_name": "Daniel", "clpid": "Grosjean-D" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis discusses the formation of aerosol particles by homogeneous nucleation of supersaturated vapor, and the subsequent or simultaneous growth of particles by condensation. Experiments, theory, and numerical simulations are used to approach the underlying goal of understanding the aerosol evolution process in photochemically reactive systems, such as Los Angeles smog.
\r\n\r\nA comprehensive size-sectionalized model was developed for simulating the evolution of a multicomponent aerosol size distribution through homogeneous nucleation, condensational growth, coagulation, and various deposition mechanisms. When applied to atmospheric photochemistry, the model predicted that the number of new particles nucleated is controlled by the ratio between the rates of homogeneous nucleation and condensational growth. A simple model was devised for predicting the number and size evolution of particles which would be formed by a burst of homogeneous nucleation. An interesting aspect of the model was its prediction of suppression of homogeneous nucleation by seed aerosol through bulk vapor depletion. Later these predictions were verified qualitatively in two systems. One was a physiochemically well characterized system where nucleation was driven by a high initial supersaturation ratio, in which nucleation was faster than predicted by classical nucleation theory, and suppression of nucleation was only slight. The second system was our outdoor smog chamber.
\r\n\r\nIn a large outdoor smog chamber, toluene and NOx were allowed to photochemically react. Gas phase concentrations and the resulting aerosol distribution were followed with time, for various initial concentrations of reactants and seed aerosol. A few thousand seed particles per cm3 (sub-ambient concentrations) were sufficient to suppress homogeneous nucleation that would have resulted in several times as many particles. Operation of the chamber in dual mode allowed the influence of a single parameter, varied between the two sides of the bag, to be clearly observed, thus avoiding many of the difficulties that arise from comparing experiments conducted at different times and different temperature and sunlight histories.
", "doi": "10.7907/0edp-5481", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:1009", "collection": "thesis", "collection_id": "1009", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03192008-083200", "primary_object_url": { "basename": "Economou_cg_1986.pdf", "content": "final", "filesize": 5532156, "license": "other", "mime_type": "application/pdf", "url": "/1009/1/Economou_cg_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "An Operator Theory Approach to Nonlinear Controller Design", "author": [ { "family_name": "Economou", "given_name": "Constantin George", "clpid": "Economou-Constantin-George" } ], "thesis_advisor": [ { "family_name": "Morari", "given_name": "Manfred", "orcid": "0000-0002-7696-5058", "clpid": "Morari-M" } ], "thesis_committee": [ { "family_name": "Morari", "given_name": "Manfred", "orcid": "0000-0002-7696-5058", "clpid": "Morari-M" }, { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Thompson", "given_name": "Peter M.", "clpid": "Thompson-Peter-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Strong similarities between control theory and the theory on the solution of operator equations have been observed and basic results in control theory have been derived from operator theory arguments. The purpose of this work is to investigate the theory of controller design as an application of basic operator theory principles and to establish a unified framework in which control theory can benefit from a \"rich\" operator theory. The major impact is anticipated in nonlinear feedback control theory: controller design can be formulated as selection of an iterative algorithm to solve a nonlinear operator equation corresponding to the control objective. As an example, controllers induced by the method of successive substitution and the Newton method are introduced and the corresponding analysis and synthesis issues are studied. Applied to linear systems, the proposed concepts have a straightforward interpretation in terms of familiar notions in linear controller design theory. Applications are presented and extensions of the current results are suggested to conclude the thesis.
", "doi": "10.7907/2ewe-dp19", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:1009", "collection": "thesis", "collection_id": "1009", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03192008-083200", "primary_object_url": { "basename": "Economou_cg_1986.pdf", "content": "final", "filesize": 5532156, "license": "other", "mime_type": "application/pdf", "url": "/1009/1/Economou_cg_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "An Operator Theory Approach to Nonlinear Controller Design", "author": [ { "family_name": "Economou", "given_name": "Constantin George", "clpid": "Economou-Constantin-George" } ], "thesis_advisor": [ { "family_name": "Morari", "given_name": "Manfred", "orcid": "0000-0002-7696-5058", "clpid": "Morari-M" } ], "thesis_committee": [ { "family_name": "Morari", "given_name": "Manfred", "orcid": "0000-0002-7696-5058", "clpid": "Morari-M" }, { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Thompson", "given_name": "Peter M.", "clpid": "Thompson-Peter-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Strong similarities between control theory and the theory on the solution of operator equations have been observed and basic results in control theory have been derived from operator theory arguments. The purpose of this work is to investigate the theory of controller design as an application of basic operator theory principles and to establish a unified framework in which control theory can benefit from a \"rich\" operator theory. The major impact is anticipated in nonlinear feedback control theory: controller design can be formulated as selection of an iterative algorithm to solve a nonlinear operator equation corresponding to the control objective. As an example, controllers induced by the method of successive substitution and the Newton method are introduced and the corresponding analysis and synthesis issues are studied. Applied to linear systems, the proposed concepts have a straightforward interpretation in terms of familiar notions in linear controller design theory. Applications are presented and extensions of the current results are suggested to conclude the thesis.
", "doi": "10.7907/2ewe-dp19", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:1118", "collection": "thesis", "collection_id": "1118", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03252008-090855", "primary_object_url": { "basename": "Russell_ag_1985.pdf", "content": "final", "filesize": 6730831, "license": "other", "mime_type": "application/pdf", "url": "/1118/1/Russell_ag_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Formation and Control of Atmospheric Aerosol Nitrate and Nitric Acid", "author": [ { "family_name": "Russell", "given_name": "Armistead Goode", "orcid": "0000-0003-2027-8870", "clpid": "Russell-Armistead-Goode" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Acosta", "given_name": "Allan J.", "clpid": "Acosta-A-J" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Sabersky", "given_name": "Rolf H.", "clpid": "Sabersky-R-H" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This work focuses on the formation, transport and control of atmospheric nitric acid and nitrate aerosol using both theoretical modeling and experimental techniques. A mathematical model was developed that describes the formation and transport of photochemically produced atmospheric gases and nitrate aerosol, using fundamental thermodynamic data to determine the quantity and state of the aerosol nitrate produced. Model predictions compared favorably with the field data available. A sensitivity study of the model indicated that the predicted aerosol nitrate concentrations are highly dependent on temperature. The trajectory model was used to study the fate of nitrogen oxides emissions and the chemical reactions responsible for the formation of atmospheric nitric acid. A majority of the NOx emissions deposit out within 24 hours, primarily as HNO3. Previously it was believed that almost all of the atmospheric nitric acid was produced during daylight hours, however model results indicate that nighttime reactions can produce comparable quantities, especially in the upper portions of the boundary layer more than a hundred meters above ground.
\r\n\r\nAn experimental program was designed and executed to collect a set of data for use in studying nitrate formation, and for use in evaluating the accuracy of air quality models. A large quantity of aerosol nitrate was observed to accumulate overnight near the coast, presumably due to the reaction between HNO3 and sea salt aerosol or soil dust\u2014like material. This aerosol is then transported inland the following afternoon, and can contribute to the high particulate nitrate levels found inland. Data from the experiment were used to test the hypothesis that atmospheric HNO3 and NH3 are in equilibrium with the aerosol phase. Most of the data are consistent with the assumption that an external mixture containing some pure NH4NO3 is present. Additional improvement is obtained if an internally mixed NH+4-NO-3-SO=4 aerosol is assumed to be present.
\r\n\r\nFurther evaluation of the air quality model against the data described above showed that the model accurately predicts the measured concentrations of O3, NO2, total nitrate, HNO3, and NH3. Representative emission control programs were tested using the model, and results indicated that NOx emission control will reduce HNO3(g), aerosol nitrate and PAN concentrations. For the particular trajectories studied, NOx control would also have reduced the peak O3 concentrations. Reducing NH3 emissions will reduce aerosol nitrate formation at the expense of increasing HNO3 concentrations. Controlling organic gas emissions will reduce O3 and PAN. Further research areas suggested by this work also are presented.
", "doi": "10.7907/rdz0-9a12", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:121", "collection": "thesis", "collection_id": "121", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01112005-133508", "primary_object_url": { "basename": "Jacob_dj_1985.pdf", "content": "final", "filesize": 17400822, "license": "other", "mime_type": "application/pdf", "url": "/121/1/Jacob_dj_1985.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Origins of Inorganic Acidity in Fogs", "author": [ { "family_name": "Jacob", "given_name": "Daniel James", "orcid": "0000-0002-6373-3100", "clpid": "Jacob-Daniel-James" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A rotating arm device to collect large samples of fogwater for chemical analysis was designed and fully characterized. This instrument was used to determine the chemical composition of fogwater at a large number of sites in California. Fogwater at both urban and non-urban sites was frequently found to contain important inorganic acidity. Chemical models were developed to interpret the origins of this acidity in terms of aqueous-phase S(IV) oxidation reactions and acid/base titration processes in the fog and the precursor atmosphere. These models were found to successfully interpret the inorganic acidity in fogwater and aerosol during wintertime stagnation episodes in the San Joaquin Valley of California.
\r\n", "doi": "10.7907/54GV-ZQ97", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:4777", "collection": "thesis", "collection_id": "4777", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12042006-093443", "primary_object_url": { "basename": "Leone_ja_1985.pdf", "content": "final", "filesize": 25379409, "license": "other", "mime_type": "application/pdf", "url": "/4777/1/Leone_ja_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Studies in Photochemical Smog Chemistry: I. Atmospheric Chemistry of Toluene. II. Analysis of Chemical Reaction Mechanisms for Photochemical Smog", "author": [ { "family_name": "Leone", "given_name": "Joseph Anthony", "clpid": "Leone-Joseph-Anthony" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Grosjean", "given_name": "Daniel", "clpid": "Grosjean-D" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This study focuses on two related topics in the gas phase organic chemistry of importance in urban air pollution. Part I describes an experimental and modeling effort aimed at developing a new explicit reaction mechanism for the atmospheric photooxidation of toluene. This mechanism is tested using experimental data from both indoor and outdoor smog chamber facilities. The predictions of the new reaction mechanism are found to be in good agreement with both sets of experimental data. Additional simulations performed with the new mechanism are used to investigate various mechanistic paths, and to gain insight into areas where our understanding is not complete. The outdoor experimental facility, which was built to provide the second set of experimental data, consists of a 65 cubic meter teflon smog chamber together with full instrumentation capable of measuring ozone, nitrogen dioxide, nitric oxide, peroxyacetyl nitrate (PAN), carbon monoxide, relative humidity, temperature, aerosol size distributions, and of course toluene and its photooxidation products.
\r\n\r\nIn Part II, we present a theoretical analysis of lumped chemical reaction mechanisms for photochemical smog. Included is a description of a new counter species analysis technique which can be used to analyze any complex chemical reaction mechanism. When applied to mechanisms for photochemical smog, this analysis is shown capable of providing answers to previously inaccessible questions such as the relative contributions of individual organics to photochemical ozone formation. The counter species analysis is applied to six existing mechanisms for photochemical smog to determine why they predict substantially different degrees of emission controls to achieve the same desired air quality under identical conditions. For each mechanism critical areas are identified that when altered bring the predictions of the various mechanisms into much closer agreement. Finally, a new lumped mechanism for photochemical smog is developed and tested against experimental data from two smog chamber facilities. Advantages of this mechanism relative to the existing lumped mechanisms are discussed.
\r\n", "doi": "10.7907/swb9-yg26", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:4777", "collection": "thesis", "collection_id": "4777", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12042006-093443", "primary_object_url": { "basename": "Leone_ja_1985.pdf", "content": "final", "filesize": 25379409, "license": "other", "mime_type": "application/pdf", "url": "/4777/1/Leone_ja_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Studies in Photochemical Smog Chemistry: I. Atmospheric Chemistry of Toluene. II. Analysis of Chemical Reaction Mechanisms for Photochemical Smog", "author": [ { "family_name": "Leone", "given_name": "Joseph Anthony", "clpid": "Leone-Joseph-Anthony" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Grosjean", "given_name": "Daniel", "clpid": "Grosjean-D" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This study focuses on two related topics in the gas phase organic chemistry of importance in urban air pollution. Part I describes an experimental and modeling effort aimed at developing a new explicit reaction mechanism for the atmospheric photooxidation of toluene. This mechanism is tested using experimental data from both indoor and outdoor smog chamber facilities. The predictions of the new reaction mechanism are found to be in good agreement with both sets of experimental data. Additional simulations performed with the new mechanism are used to investigate various mechanistic paths, and to gain insight into areas where our understanding is not complete. The outdoor experimental facility, which was built to provide the second set of experimental data, consists of a 65 cubic meter teflon smog chamber together with full instrumentation capable of measuring ozone, nitrogen dioxide, nitric oxide, peroxyacetyl nitrate (PAN), carbon monoxide, relative humidity, temperature, aerosol size distributions, and of course toluene and its photooxidation products.
\r\n\r\nIn Part II, we present a theoretical analysis of lumped chemical reaction mechanisms for photochemical smog. Included is a description of a new counter species analysis technique which can be used to analyze any complex chemical reaction mechanism. When applied to mechanisms for photochemical smog, this analysis is shown capable of providing answers to previously inaccessible questions such as the relative contributions of individual organics to photochemical ozone formation. The counter species analysis is applied to six existing mechanisms for photochemical smog to determine why they predict substantially different degrees of emission controls to achieve the same desired air quality under identical conditions. For each mechanism critical areas are identified that when altered bring the predictions of the various mechanisms into much closer agreement. Finally, a new lumped mechanism for photochemical smog is developed and tested against experimental data from two smog chamber facilities. Advantages of this mechanism relative to the existing lumped mechanisms are discussed.
\r\n", "doi": "10.7907/swb9-yg26", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:1332", "collection": "thesis", "collection_id": "1332", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04102008-112738", "primary_object_url": { "basename": "Biswas_p_1985.pdf", "content": "final", "filesize": 23461308, "license": "other", "mime_type": "application/pdf", "url": "/1332/1/Biswas_p_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Impactors for Aerosol Measurement: Developments and Sampling Biases", "author": [ { "family_name": "Biswas", "given_name": "Pratim", "clpid": "Biswas-Pratim" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Brennen", "given_name": "Christopher E.", "clpid": "Brennen-C-E" }, { "family_name": "Sabersky", "given_name": "Rolf H.", "clpid": "Sabersky-R-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This work is subdivided into four parts. The first part consists of characterizing high jet velocity impactors, developing their scaling criteria to facilitate instrument design and prediction of impactor performance under conditions where no calibration data are available.
\r\n\r\nThe second part discusses the problem of distortion of size distributions by aerosol sampling instruments because of particle size changes occurring due to vapor or condensable phase transport to and from the particles. The severity of the problem is demonstrated both theoretically and experimentally for a few commonly used aerosol sampling instruments.
\r\n\r\nThe third part is the development of a 'Particle Trap Impactor' working on the virtual impaction principle. The inherent problems of bounce and re-entrainment in conventional impactors is minimized, without the addition of substrates such as grease, in these impactors. The result of operating the unit at high temperature is also discussed.
\r\n\r\nThe final part is the calculation of the scavenging rate of particles due to differential impaction. The results are used to determine upperbounds on the number concentration of particles entering the impactor to minimize biasing the measurements.
", "doi": "10.7907/YG7P-PX37", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:1332", "collection": "thesis", "collection_id": "1332", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04102008-112738", "primary_object_url": { "basename": "Biswas_p_1985.pdf", "content": "final", "filesize": 23461308, "license": "other", "mime_type": "application/pdf", "url": "/1332/1/Biswas_p_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Impactors for Aerosol Measurement: Developments and Sampling Biases", "author": [ { "family_name": "Biswas", "given_name": "Pratim", "clpid": "Biswas-Pratim" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Brennen", "given_name": "Christopher E.", "clpid": "Brennen-C-E" }, { "family_name": "Sabersky", "given_name": "Rolf H.", "clpid": "Sabersky-R-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This work is subdivided into four parts. The first part consists of characterizing high jet velocity impactors, developing their scaling criteria to facilitate instrument design and prediction of impactor performance under conditions where no calibration data are available.
\r\n\r\nThe second part discusses the problem of distortion of size distributions by aerosol sampling instruments because of particle size changes occurring due to vapor or condensable phase transport to and from the particles. The severity of the problem is demonstrated both theoretically and experimentally for a few commonly used aerosol sampling instruments.
\r\n\r\nThe third part is the development of a 'Particle Trap Impactor' working on the virtual impaction principle. The inherent problems of bounce and re-entrainment in conventional impactors is minimized, without the addition of substrates such as grease, in these impactors. The result of operating the unit at high temperature is also discussed.
\r\n\r\nThe final part is the calculation of the scavenging rate of particles due to differential impaction. The results are used to determine upperbounds on the number concentration of particles entering the impactor to minimize biasing the measurements.
", "doi": "10.7907/YG7P-PX37", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:1345", "collection": "thesis", "collection_id": "1345", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04112008-112307", "primary_object_url": { "basename": "Bentley_bj_1985.pdf", "content": "final", "filesize": 12313204, "license": "other", "mime_type": "application/pdf", "url": "/1345/1/Bentley_bj_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Drop Deformation and Burst in Two-Dimensional Flows", "author": [ { "family_name": "Bentley", "given_name": "Barry Jerome", "clpid": "Bentley-Barry-Jerome" } ], "thesis_advisor": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" } ], "thesis_committee": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Herbolzheimer", "given_name": "Eric", "clpid": "Herbolzheimer-E" }, { "family_name": "Acrivos", "given_name": "Andreas", "clpid": "Acrivos-Andreas" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The deformation and burst of small fluid droplets suspended in a second immiscible fluid undergoing a steady linear shearing motion are discussed. The effects of Capillary number, ratio of fluid viscosities, and flow type are considered both experimentally and theoretically.
\r\n\r\nThe experiments are unique in that a spectrum of strong two-dimensional flows (those with the magnitude of the strain rate exceeding that of the vorticity) was considered. These flows were generated in a four roll mill specifically designed for the experiments. Previous investigations had been limited to one specific strong flow owing to the difficulty in holding drops stationary at the stagnation point in such flows. We overcame this obstacle by using a computer interfaced to a digital video camera to locate the drops in the flow field and adjust the roller speeds to effect an inferential feedback control scheme. It is believed that the control system implemented for the present experiments could be adapted to a variety of fluid flow experiments with similar control problems.
\r\n\r\nDrop deformation and burst experiments were performed for viscosity ratios ranging from 0.001 to 27., and flows with ratio of vorticity to strain rate ranging from zero to 0.667. In a typical experiment a drop went through a succession of increasingly deformed steady shapes as the Capillary number was slowly increased with the flow type constant. The appearance of the drop was recorded photographically. In most cases, a Capillary number was reached where no steady shape was possible, and this was recorded as the critical Capillary number for drop burst. In a few cases with high viscosity ratio and large vorticity to strain rate ratio, drop burst was impossible. In cases where burst occurred, the transient motion of the drops at the critical Capillary number was observed. The drops continued to deform, but did not break into fragments until the flow was turned off. They then either fragmented or returned to the spherical shape through a complex interfacial tension driven motion.
\r\n\r\nThe experimental deformation and burst observations were compared to the predictions of several available theories. Separate theories apply to cases where the deformation is small (nearly spherical drops) or large (threadlike drops). Comparisons to existing numerical results for one particular viscosity ratio are also included. Agreement between the experimental observations and the predictions of the theories was very good.
\r\n", "doi": "10.7907/2axg-ce38", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:1330", "collection": "thesis", "collection_id": "1330", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04102008-092241", "primary_object_url": { "basename": "Davison_bh_1985.pdf", "content": "final", "filesize": 5807192, "license": "other", "mime_type": "application/pdf", "url": "/1330/1/Davison_bh_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Dynamics and Coexistence of Microbial Mixed Cultures", "author": [ { "family_name": "Davison", "given_name": "Brian Henry", "orcid": "0000-0002-7408-3609", "clpid": "Davison-Brian-Henry" } ], "thesis_advisor": [ { "family_name": "Stephanopoulos", "given_name": "Gregory N.", "clpid": "Stephanopoulos-G-N" } ], "thesis_committee": [ { "family_name": "Stephanopoulos", "given_name": "Gregory N.", "clpid": "Stephanopoulos-G-N" }, { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Various methods of establishing a persistent mixed culture were examined in continuous culture. A well-defined system consisting of Esherichia coli and Saccharomyces cerevisiae was used. The primary interaction was competition for glucose, the rate limiting nutrient. When this was the only interaction no coexistence is possible in a well mixed fermentor at constant conditions (i.e., a chemostat).
\r\n\r\nThe two microorganisms while competing for glucose were maintained in a stable cycle of coexistence by alternating the growth advantage between the two organisms by oscillating the pH in a chemostat. Pure culture experiments found S. cerevisiae to be insensitve to pH between 5 and 4.3 with a maximum specific growth rate (Umax) of 0.4/hr; while Umax of E. coli decreased from 0.6/hr at pH 5 to 0.1/hr at pH 4.3. Steady state and crossinoculation chemostat runs at a dilution rate of 0.17/hr confirmed the expectation that the mixed culture system is unstable at constant pH with E. coli dominating at pH 5 and S. cerevisiae dominating at pH 4.3. Three pH oscillation experiments were performed at D=0.17/hr with 1 gm/1 glucose feed. The 16 hr/16 hr cycle was stable for six periods with a stable alternating cycle of E. coli and S. cerevisiae being quickly established. A 18 hr pH5./14 hr pH4.3 cycle was found to be stable with smaller yeast concentrations. A 6hr/6hr cycle was found unstable with yeast washout. Simulation results were compared with these runs and were used to predict the onset of instability. Oscillations of pH can force stable persistence of a competing mixed culture that is otherwise unstable. Thus time varying conditions are experimentally demonstrated to be one explanation for competitive coexistence.
\r\n\r\nA mixed culture of Saccharomyces cerevisiae and Esherichia coli was established in a stable coexistence steady state in a chemostat under constant operating conditions at higher feed concentrations. The species competed for glucose, the growth limiting resource, and produced acetate and ethanol. The acetic acid was shown to be very inhibitory to E. coli in pure culture at pH 5 while ethanol inhibition was only marginal. No significant inhibition of S. cerevisiae growth was observed by either acetate or ethanol. Pure culture paramenters were measured and used in the analysis. Linearized stabilty analysis for the case when both organisms produce the inhibitor showed that a transition through three stable outcomes was possible as the feed concentration is lowered. Experimental studies verified these predictions and successive transitions from a yeast growth steady state, to a coexistence steady state, and to a E. coli growth steady state were obtained by lowering the glucose concentration in the feed from 10 to 5 to 2.5 g/l. This dynamic behavior is distinctly different form other competition-inhibition combinations and demostrates for the first time that coexistence is possible due to substrate competition and product inhibition.
\r\n\r\nA bioreactor with simultaneous fermentation and cell recycle was investigated. The reactor consisted of a typical fermentor and an attached inclined side-arm that allowed enhanced sedimentation. Due to the enhanced sedimentation in the side-arm settler the cells precipitate quickly and flow back into the reactor. A virtually cell free broth can be withdrawn through the side-arm while maintaining both a high flowrate and a high cell density. Continuous fermentations with S. cerevisiae demonstrated these features and the possibility of high cell densities at flowrates that ordinarially would lead to washout. Ethanol productivities and yields were high. Increased resistance to contamination was feasible and tested using E. coli as the model contaminant.
\r\n\r\nThis new reactor with size-selective properties was found to allow a coexistent mixed culture of Esherichia coli and Saccharomyces cerevisiae. The larger yeast population was retained and recycled at high efficiencies, while the smaller yet faster growing bacteria were removed preferentially through the side-arm. Stability analysis indicated that the coexistence of this system could be stable only if the yeast removal rate as a function of biomass was concave up. This would occur if growth continued in the side-arm. Another experimental system was devised to measure this removal rate function. A negative removal rate (i.e., a net addition of yeast to the fermentor) was observed at low biomass indicating growth in the settler and explaining the stability of the coexistence steady state.
\r\n\r\nA mixed culture, that was unstable during pure competition under constant well-mixed conditions as expressed in the Competitive Exclusion Principle, was made to persist indefinitely by the use of time-varying conditions (such as pH oscillations), or the addition of other interactions (such as inhibition), or the design of spatially nonuniform reactors (such as the side-arm settler).
", "doi": "10.7907/EC5N-4Y46", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:1118", "collection": "thesis", "collection_id": "1118", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03252008-090855", "primary_object_url": { "basename": "Russell_ag_1985.pdf", "content": "final", "filesize": 6730831, "license": "other", "mime_type": "application/pdf", "url": "/1118/1/Russell_ag_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Formation and Control of Atmospheric Aerosol Nitrate and Nitric Acid", "author": [ { "family_name": "Russell", "given_name": "Armistead Goode", "orcid": "0000-0003-2027-8870", "clpid": "Russell-Armistead-Goode" } ], "thesis_advisor": [ { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "thesis_committee": [ { "family_name": "Acosta", "given_name": "Allan J.", "clpid": "Acosta-A-J" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Sabersky", "given_name": "Rolf H.", "clpid": "Sabersky-R-H" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This work focuses on the formation, transport and control of atmospheric nitric acid and nitrate aerosol using both theoretical modeling and experimental techniques. A mathematical model was developed that describes the formation and transport of photochemically produced atmospheric gases and nitrate aerosol, using fundamental thermodynamic data to determine the quantity and state of the aerosol nitrate produced. Model predictions compared favorably with the field data available. A sensitivity study of the model indicated that the predicted aerosol nitrate concentrations are highly dependent on temperature. The trajectory model was used to study the fate of nitrogen oxides emissions and the chemical reactions responsible for the formation of atmospheric nitric acid. A majority of the NOx emissions deposit out within 24 hours, primarily as HNO3. Previously it was believed that almost all of the atmospheric nitric acid was produced during daylight hours, however model results indicate that nighttime reactions can produce comparable quantities, especially in the upper portions of the boundary layer more than a hundred meters above ground.
\r\n\r\nAn experimental program was designed and executed to collect a set of data for use in studying nitrate formation, and for use in evaluating the accuracy of air quality models. A large quantity of aerosol nitrate was observed to accumulate overnight near the coast, presumably due to the reaction between HNO3 and sea salt aerosol or soil dust\u2014like material. This aerosol is then transported inland the following afternoon, and can contribute to the high particulate nitrate levels found inland. Data from the experiment were used to test the hypothesis that atmospheric HNO3 and NH3 are in equilibrium with the aerosol phase. Most of the data are consistent with the assumption that an external mixture containing some pure NH4NO3 is present. Additional improvement is obtained if an internally mixed NH+4-NO-3-SO=4 aerosol is assumed to be present.
\r\n\r\nFurther evaluation of the air quality model against the data described above showed that the model accurately predicts the measured concentrations of O3, NO2, total nitrate, HNO3, and NH3. Representative emission control programs were tested using the model, and results indicated that NOx emission control will reduce HNO3(g), aerosol nitrate and PAN concentrations. For the particular trajectories studied, NOx control would also have reduced the peak O3 concentrations. Reducing NH3 emissions will reduce aerosol nitrate formation at the expense of increasing HNO3 concentrations. Controlling organic gas emissions will reduce O3 and PAN. Further research areas suggested by this work also are presented.
", "doi": "10.7907/rdz0-9a12", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:1345", "collection": "thesis", "collection_id": "1345", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04112008-112307", "primary_object_url": { "basename": "Bentley_bj_1985.pdf", "content": "final", "filesize": 12313204, "license": "other", "mime_type": "application/pdf", "url": "/1345/1/Bentley_bj_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Drop Deformation and Burst in Two-Dimensional Flows", "author": [ { "family_name": "Bentley", "given_name": "Barry Jerome", "clpid": "Bentley-Barry-Jerome" } ], "thesis_advisor": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" } ], "thesis_committee": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Herbolzheimer", "given_name": "Eric", "clpid": "Herbolzheimer-E" }, { "family_name": "Acrivos", "given_name": "Andreas", "clpid": "Acrivos-Andreas" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The deformation and burst of small fluid droplets suspended in a second immiscible fluid undergoing a steady linear shearing motion are discussed. The effects of Capillary number, ratio of fluid viscosities, and flow type are considered both experimentally and theoretically.
\r\n\r\nThe experiments are unique in that a spectrum of strong two-dimensional flows (those with the magnitude of the strain rate exceeding that of the vorticity) was considered. These flows were generated in a four roll mill specifically designed for the experiments. Previous investigations had been limited to one specific strong flow owing to the difficulty in holding drops stationary at the stagnation point in such flows. We overcame this obstacle by using a computer interfaced to a digital video camera to locate the drops in the flow field and adjust the roller speeds to effect an inferential feedback control scheme. It is believed that the control system implemented for the present experiments could be adapted to a variety of fluid flow experiments with similar control problems.
\r\n\r\nDrop deformation and burst experiments were performed for viscosity ratios ranging from 0.001 to 27., and flows with ratio of vorticity to strain rate ranging from zero to 0.667. In a typical experiment a drop went through a succession of increasingly deformed steady shapes as the Capillary number was slowly increased with the flow type constant. The appearance of the drop was recorded photographically. In most cases, a Capillary number was reached where no steady shape was possible, and this was recorded as the critical Capillary number for drop burst. In a few cases with high viscosity ratio and large vorticity to strain rate ratio, drop burst was impossible. In cases where burst occurred, the transient motion of the drops at the critical Capillary number was observed. The drops continued to deform, but did not break into fragments until the flow was turned off. They then either fragmented or returned to the spherical shape through a complex interfacial tension driven motion.
\r\n\r\nThe experimental deformation and burst observations were compared to the predictions of several available theories. Separate theories apply to cases where the deformation is small (nearly spherical drops) or large (threadlike drops). Comparisons to existing numerical results for one particular viscosity ratio are also included. Agreement between the experimental observations and the predictions of the theories was very good.
\r\n", "doi": "10.7907/2axg-ce38", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:121", "collection": "thesis", "collection_id": "121", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01112005-133508", "primary_object_url": { "basename": "Jacob_dj_1985.pdf", "content": "final", "filesize": 17400822, "license": "other", "mime_type": "application/pdf", "url": "/121/1/Jacob_dj_1985.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Origins of Inorganic Acidity in Fogs", "author": [ { "family_name": "Jacob", "given_name": "Daniel James", "orcid": "0000-0002-6373-3100", "clpid": "Jacob-Daniel-James" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A rotating arm device to collect large samples of fogwater for chemical analysis was designed and fully characterized. This instrument was used to determine the chemical composition of fogwater at a large number of sites in California. Fogwater at both urban and non-urban sites was frequently found to contain important inorganic acidity. Chemical models were developed to interpret the origins of this acidity in terms of aqueous-phase S(IV) oxidation reactions and acid/base titration processes in the fog and the precursor atmosphere. These models were found to successfully interpret the inorganic acidity in fogwater and aerosol during wintertime stagnation episodes in the San Joaquin Valley of California.
\r\n", "doi": "10.7907/54GV-ZQ97", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:11331", "collection": "thesis", "collection_id": "11331", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01032019-104846124", "primary_object_url": { "basename": "Weston_TA_1985.pdf", "content": "final", "filesize": 35690789, "license": "other", "mime_type": "application/pdf", "url": "/11331/1/Weston_TA_1985.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "The Regeneration of High Temperature Sulfur Dioxide Sorbents: the CO Reduction of Supported Alkali Sulfates", "author": [ { "family_name": "Weston", "given_name": "Theresa Ann", "orcid": "0000-0002-9822-7355", "clpid": "Weston-Theresa-Ann" } ], "thesis_advisor": [ { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" } ], "thesis_committee": [ { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Voecks", "given_name": "Gerald E.", "orcid": "0009-0008-9371-5756", "clpid": "Voecks-Gerald-E" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The chemical reactions involved in the regeneration step of a high temperature SO2 removal process have been investigated. In particular, the CO reduction of supported alkali sulfates has been studied. Thermogravimetric measurements have yielded the time-resolved composition of sorbent and gaseous products during reduction with 10% CO at 700 and 800\u00b0C. FTIR was used to identify reaction intermediates . A flow microreactor was used to compare gaseous product selectivity between SO2, COS and elemental sulfur of sorbents reduced with 1 and 10% CO at 700 and 800\u00b0C.
\r\n\r\nThe experimental results show regeneration; i.e., sulfur removal is greatly increased by the presence of lithium in the sorbent material. Reaction between the support and the alkali material greatly influences the degree of regeneration. Support materials are apparently active in the catalysis of the reduction of SO2 to elemental sulfur and the reaction between elemental sulfur and CO to form COS, and therefore, influences the product selectivity. A reaction scheme which qualitatively explains the experimental results is proposed.
\r\n", "doi": "10.7907/cen1-hb98", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:1160", "collection": "thesis", "collection_id": "1160", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03262008-141334", "primary_object_url": { "basename": "Faust_bc_1985.pdf", "content": "final", "filesize": 4202814, "license": "other", "mime_type": "application/pdf", "url": "/1160/1/Faust_bc_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Photo-Induced Reductive Dissolution of Hematite (\u03b1-Fe\u2082O\u2083) by S(IV) Oxyanions", "author": [ { "family_name": "Faust", "given_name": "Bruce Charles", "orcid": "0009-0001-2881-6533", "clpid": "Faust-Bruce-Charles" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The kinetics and mechanism of the photo-induced reductive dissolution of hematite (\u03b1-Fe2O3) by S(IV) oxyanions, in aqueous suspensions of hematite, have been investigated. Experimental quantum yields for Fe(II)aq production are reported for deoxygenated hematite suspensions containing S(IV). Quantum yield studies together with spectroscopic information indicate that \u2261Fe(III)-S(IV) surface complexes undergo a photo-induced ligand to metal charge transfer reaction resulting in the reductive dissolution of hematite and production of Fe(II)aq.
\r\n\r\nThe autoxidation of S(IV) in oxygenated hematite suspensions exhibits autocatalytic behavior. This behavior is interpreted in terms of three general processes: i) production of Fe(II)aq from photo-induced ligand to metal charge transfer reactions of \u2261Fe(III)-S(IV) surface complexes, ii) oxidation of Fe(II)aq to Fe(III)aq and, iii) the Fe(III)aq catalyzed autoxidation of S(IV). A numerical model, based on these processes, is developed to predict the disappearance of S(IV) in oxygenated hematite suspensions under illumination.
", "doi": "10.7907/cj3r-5x15", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:2786", "collection": "thesis", "collection_id": "2786", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06302005-124544", "primary_object_url": { "basename": "Yang_s-m_1985.pdf", "content": "final", "filesize": 8447113, "license": "other", "mime_type": "application/pdf", "url": "/2786/1/Yang_s-m_1985.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Hydrodynamics and Brownian Motion of Small Particles Near a Fluid-Fluid Interface", "author": [ { "family_name": "Yang", "given_name": "Seung-Man", "clpid": "Yang-Seung-Man" } ], "thesis_advisor": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" } ], "thesis_committee": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Wu", "given_name": "Theodore Yao-tsu", "clpid": "Wu-T-Y-T" }, { "family_name": "Herbolzheimer", "given_name": "Eric", "clpid": "Herbolzheimer-E" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The general problems of particle motion in the vicinity of a flat, non-deforming fluid interface is studied. The approximate singularity method used by previous workers in this research group has been generalized to consider the motion of a sphere in any linear velocity field compatible with the existence of the undisturbed flat interface, and the motion of slender rod-like particles which undergo an arbitrary translation or rotation in either a quiescent fluid or in a linear flow. The theory yields the hydrodynamic mobility tensors which are necessary to describe Brownian movement near a phase boundary, as well as general trajectory equations for sedimenting particles near a fluid interface with an arbitrary viscosity ratio. These approximate solution results are in good agreement with both exact-solutions where they are available and experimental data for motion of a sphere near a rigid plane wall. Among the most interesting results for motion of slender bodies is the generalization of Jeffery orbit equations for linear simple shear flow.
\r\n\r\nThe Brownian motion of a sphere in the presence of a deformable fluid interface is also examined. First, the fluctuation-dissipation theorem is derived for the random distortions of interface shape that are caused by spontaneous thermal impulses from the surrounding fluids. This analysis is carried out using the method of normal modes in conjunction with a Langevim type equation for the Brownian particle, and results in the prediction of autocorrelation functions for the location of the interface, for the random force acting on the particle (evaluated by a generalization of the Faxen's law), and for the particle velocity. The particle velocity correlation, in turn, yields the effective diffusion coefficient due to random fluctuations of the interface shape. Finally, we investigate the effects of interface deformation that are induced by the impulsive motion of a sphere that is undergoing Brownian motion. In this phase of our study, we consider both the spatially modified hydrodynamic mobility which occurs as a consequence of hydrodynamic interactions, and influence on the mean-square displacement of the Brownian particle of the interface relaxation back towards the flat equilibrium configuration after an initial deformation that is caused by the particle motion.
", "doi": "10.7907/jvmx-rd64", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:2786", "collection": "thesis", "collection_id": "2786", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06302005-124544", "primary_object_url": { "basename": "Yang_s-m_1985.pdf", "content": "final", "filesize": 8447113, "license": "other", "mime_type": "application/pdf", "url": "/2786/1/Yang_s-m_1985.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Hydrodynamics and Brownian Motion of Small Particles Near a Fluid-Fluid Interface", "author": [ { "family_name": "Yang", "given_name": "Seung-Man", "clpid": "Yang-Seung-Man" } ], "thesis_advisor": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" } ], "thesis_committee": [ { "family_name": "Leal", "given_name": "L. Gary", "clpid": "Leal-L-G" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Wu", "given_name": "Theodore Yao-tsu", "clpid": "Wu-T-Y-T" }, { "family_name": "Herbolzheimer", "given_name": "Eric", "clpid": "Herbolzheimer-E" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The general problems of particle motion in the vicinity of a flat, non-deforming fluid interface is studied. The approximate singularity method used by previous workers in this research group has been generalized to consider the motion of a sphere in any linear velocity field compatible with the existence of the undisturbed flat interface, and the motion of slender rod-like particles which undergo an arbitrary translation or rotation in either a quiescent fluid or in a linear flow. The theory yields the hydrodynamic mobility tensors which are necessary to describe Brownian movement near a phase boundary, as well as general trajectory equations for sedimenting particles near a fluid interface with an arbitrary viscosity ratio. These approximate solution results are in good agreement with both exact-solutions where they are available and experimental data for motion of a sphere near a rigid plane wall. Among the most interesting results for motion of slender bodies is the generalization of Jeffery orbit equations for linear simple shear flow.
\r\n\r\nThe Brownian motion of a sphere in the presence of a deformable fluid interface is also examined. First, the fluctuation-dissipation theorem is derived for the random distortions of interface shape that are caused by spontaneous thermal impulses from the surrounding fluids. This analysis is carried out using the method of normal modes in conjunction with a Langevim type equation for the Brownian particle, and results in the prediction of autocorrelation functions for the location of the interface, for the random force acting on the particle (evaluated by a generalization of the Faxen's law), and for the particle velocity. The particle velocity correlation, in turn, yields the effective diffusion coefficient due to random fluctuations of the interface shape. Finally, we investigate the effects of interface deformation that are induced by the impulsive motion of a sphere that is undergoing Brownian motion. In this phase of our study, we consider both the spatially modified hydrodynamic mobility which occurs as a consequence of hydrodynamic interactions, and influence on the mean-square displacement of the Brownian particle of the interface relaxation back towards the flat equilibrium configuration after an initial deformation that is caused by the particle motion.
", "doi": "10.7907/jvmx-rd64", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:1160", "collection": "thesis", "collection_id": "1160", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03262008-141334", "primary_object_url": { "basename": "Faust_bc_1985.pdf", "content": "final", "filesize": 4202814, "license": "other", "mime_type": "application/pdf", "url": "/1160/1/Faust_bc_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Photo-Induced Reductive Dissolution of Hematite (\u03b1-Fe\u2082O\u2083) by S(IV) Oxyanions", "author": [ { "family_name": "Faust", "given_name": "Bruce Charles", "orcid": "0009-0001-2881-6533", "clpid": "Faust-Bruce-Charles" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "orcid": "0000-0001-6495-1946", "clpid": "Hoffmann-M-R" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The kinetics and mechanism of the photo-induced reductive dissolution of hematite (\u03b1-Fe2O3) by S(IV) oxyanions, in aqueous suspensions of hematite, have been investigated. Experimental quantum yields for Fe(II)aq production are reported for deoxygenated hematite suspensions containing S(IV). Quantum yield studies together with spectroscopic information indicate that \u2261Fe(III)-S(IV) surface complexes undergo a photo-induced ligand to metal charge transfer reaction resulting in the reductive dissolution of hematite and production of Fe(II)aq.
\r\n\r\nThe autoxidation of S(IV) in oxygenated hematite suspensions exhibits autocatalytic behavior. This behavior is interpreted in terms of three general processes: i) production of Fe(II)aq from photo-induced ligand to metal charge transfer reactions of \u2261Fe(III)-S(IV) surface complexes, ii) oxidation of Fe(II)aq to Fe(III)aq and, iii) the Fe(III)aq catalyzed autoxidation of S(IV). A numerical model, based on these processes, is developed to predict the disappearance of S(IV) in oxygenated hematite suspensions under illumination.
", "doi": "10.7907/cj3r-5x15", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:1330", "collection": "thesis", "collection_id": "1330", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04102008-092241", "primary_object_url": { "basename": "Davison_bh_1985.pdf", "content": "final", "filesize": 5807192, "license": "other", "mime_type": "application/pdf", "url": "/1330/1/Davison_bh_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Dynamics and Coexistence of Microbial Mixed Cultures", "author": [ { "family_name": "Davison", "given_name": "Brian Henry", "orcid": "0000-0002-7408-3609", "clpid": "Davison-Brian-Henry" } ], "thesis_advisor": [ { "family_name": "Stephanopoulos", "given_name": "Gregory N.", "clpid": "Stephanopoulos-G-N" } ], "thesis_committee": [ { "family_name": "Stephanopoulos", "given_name": "Gregory N.", "clpid": "Stephanopoulos-G-N" }, { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Various methods of establishing a persistent mixed culture were examined in continuous culture. A well-defined system consisting of Esherichia coli and Saccharomyces cerevisiae was used. The primary interaction was competition for glucose, the rate limiting nutrient. When this was the only interaction no coexistence is possible in a well mixed fermentor at constant conditions (i.e., a chemostat).
\r\n\r\nThe two microorganisms while competing for glucose were maintained in a stable cycle of coexistence by alternating the growth advantage between the two organisms by oscillating the pH in a chemostat. Pure culture experiments found S. cerevisiae to be insensitve to pH between 5 and 4.3 with a maximum specific growth rate (Umax) of 0.4/hr; while Umax of E. coli decreased from 0.6/hr at pH 5 to 0.1/hr at pH 4.3. Steady state and crossinoculation chemostat runs at a dilution rate of 0.17/hr confirmed the expectation that the mixed culture system is unstable at constant pH with E. coli dominating at pH 5 and S. cerevisiae dominating at pH 4.3. Three pH oscillation experiments were performed at D=0.17/hr with 1 gm/1 glucose feed. The 16 hr/16 hr cycle was stable for six periods with a stable alternating cycle of E. coli and S. cerevisiae being quickly established. A 18 hr pH5./14 hr pH4.3 cycle was found to be stable with smaller yeast concentrations. A 6hr/6hr cycle was found unstable with yeast washout. Simulation results were compared with these runs and were used to predict the onset of instability. Oscillations of pH can force stable persistence of a competing mixed culture that is otherwise unstable. Thus time varying conditions are experimentally demonstrated to be one explanation for competitive coexistence.
\r\n\r\nA mixed culture of Saccharomyces cerevisiae and Esherichia coli was established in a stable coexistence steady state in a chemostat under constant operating conditions at higher feed concentrations. The species competed for glucose, the growth limiting resource, and produced acetate and ethanol. The acetic acid was shown to be very inhibitory to E. coli in pure culture at pH 5 while ethanol inhibition was only marginal. No significant inhibition of S. cerevisiae growth was observed by either acetate or ethanol. Pure culture paramenters were measured and used in the analysis. Linearized stabilty analysis for the case when both organisms produce the inhibitor showed that a transition through three stable outcomes was possible as the feed concentration is lowered. Experimental studies verified these predictions and successive transitions from a yeast growth steady state, to a coexistence steady state, and to a E. coli growth steady state were obtained by lowering the glucose concentration in the feed from 10 to 5 to 2.5 g/l. This dynamic behavior is distinctly different form other competition-inhibition combinations and demostrates for the first time that coexistence is possible due to substrate competition and product inhibition.
\r\n\r\nA bioreactor with simultaneous fermentation and cell recycle was investigated. The reactor consisted of a typical fermentor and an attached inclined side-arm that allowed enhanced sedimentation. Due to the enhanced sedimentation in the side-arm settler the cells precipitate quickly and flow back into the reactor. A virtually cell free broth can be withdrawn through the side-arm while maintaining both a high flowrate and a high cell density. Continuous fermentations with S. cerevisiae demonstrated these features and the possibility of high cell densities at flowrates that ordinarially would lead to washout. Ethanol productivities and yields were high. Increased resistance to contamination was feasible and tested using E. coli as the model contaminant.
\r\n\r\nThis new reactor with size-selective properties was found to allow a coexistent mixed culture of Esherichia coli and Saccharomyces cerevisiae. The larger yeast population was retained and recycled at high efficiencies, while the smaller yet faster growing bacteria were removed preferentially through the side-arm. Stability analysis indicated that the coexistence of this system could be stable only if the yeast removal rate as a function of biomass was concave up. This would occur if growth continued in the side-arm. Another experimental system was devised to measure this removal rate function. A negative removal rate (i.e., a net addition of yeast to the fermentor) was observed at low biomass indicating growth in the settler and explaining the stability of the coexistence steady state.
\r\n\r\nA mixed culture, that was unstable during pure competition under constant well-mixed conditions as expressed in the Competitive Exclusion Principle, was made to persist indefinitely by the use of time-varying conditions (such as pH oscillations), or the addition of other interactions (such as inhibition), or the design of spatially nonuniform reactors (such as the side-arm settler).
", "doi": "10.7907/EC5N-4Y46", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:4569", "collection": "thesis", "collection_id": "4569", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11152005-102832", "primary_object_url": { "basename": "Gray_mr_1984.pdf", "content": "final", "filesize": 15456370, "license": "other", "mime_type": "application/pdf", "url": "/4569/1/Gray_mr_1984.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "The Effects of Moisture and Ash Content on the Pyrolysis of a Wood Derived Material", "author": [ { "family_name": "Gray", "given_name": "Murray Ross", "orcid": "0000-0003-2431-7312", "clpid": "Gray-Murray-Ross" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Qader", "given_name": "Shaik A.", "clpid": "Qader-Shaik-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Moisture and ash are always present in wood to some extent, but their affect on its chemical behavior is not fully known. The influence of moisture and ash on the thermal degradation of wood was investigated by pyrolyzing samples of ground wood waste in a batch fluid-bed reactor at between 320 and 470\u00b0C in helium at 101-104 kPa. The wood samples were heated at about 300\u00b0C/min. so that drying and pyrolysis were simultaneous, Woodex\u00ae pellets were used in this study because their density was suitable for fluid-bed tests.
\r\n\r\nIn ash-free samples moisture suppressed the formation of pyrolysis tar at temperatures above 390\u00baC and increased the yield of char, relative to dry samples. A model for the behavior of free radicals during pyrolysis is proposed which gives qualitative agreement with the observed effect of temperature. The ion-exchange capacity of wood was used to disperse calcium atoms in the polymer matrix, which increased the formation of aqueous product during pyrolysis at the expense of tar by enhancing dehydration and fragmentation reactions. The native mineral components in the wood waste gave effects equivalent to calcium.
\r\n\r\nThe effect of moisture on char yield was independent of the ash components, but the yield of tar from Woodex containing moisture and ash exhibited a minimum at 390\u00b0C. Below 390\u00b0C the water hydrated catalyst sites to reduce reactivity. A kinetic model for hydration gave qualitative agreement with the observed effects of temperature. Above 390\u00b0C the degradation of tar became independent of the availability of catalyst sites, and was suppressed by the effect of water on the concentration of tar within the particles, and on the equilibrium of dehydration reactions.
", "doi": "10.7907/ZEMV-CV64", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:1814", "collection": "thesis", "collection_id": "1814", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05152003-160535", "type": "thesis", "title": "Control Model Development for Packed Bed Chemical Reactors", "author": [ { "family_name": "Khanna", "given_name": "Rohit", "clpid": "Khanna-Rohit" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Bailey", "given_name": "James E.", "clpid": "Bailey-J-E" }, { "family_name": "Morari", "given_name": "Manfred", "orcid": "0000-0002-7696-5058", "clpid": "Morari-M" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Although control algorithms have been conceived for industrial chemical systems, their acceptance by industry has been slow due to a lack of direct experimental evidence of their effectiveness and to volumes of conflicting, or at least incompatible, recommendations on control structure design. This thesis provides the basis for a concerted theoretical and experimental program in multivariable process control structure design for packed bed chemical reactors by presenting an in-depth control analysis of a practical, multivariable, distributed parameter system-the heat conduction problem defined by the simple diffusion equation-using both frequency-domain and time-domain analyses and the formulation, numerical solution, and analysis of a detailed model for packed bed reactors, along with reduction to a low-order state-space representation suitable for on-line process control.
\r\n\r\nThe study of the heat conduction system allowed for consideration of various control design techniques and the relation between measurement structure and control system design. This study shows that the choice of measurements and their locations significantly affects the optimal control design and the usefulness of the different design techniques and the importance of an accurate process model and the necessity of model reduction to a low-order state-space representation for control structure design and implementation.
\r\n\r\nThe second portion of this study provides a detailed mathematical modeling analysis of packed bed catalytic reactors that significantly extends previous studies in the detail of the model and in the consideration of all aspects of the model development and reduction to a state-space control representation. The general view that modeling simplifications are desired since they lead to a reduction in numerical solution effort is contested, and it is shown that many simplifications are no longer necessary with today's advanced computational capabilities. A unified approach to dynamic reactor modeling is developed and its importance in the accurate description of dynamic and steady state reactor behavior, in the investigation of reactor start-up or the effects of process disturbances, and in the development of an accurate reduced state-space model for the design of control structures to stabilize the reactor under various disturbances or to provide optimal system recovery from input changes is shown.
\r\n", "doi": "10.7907/VK3Y-QN30", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:85", "collection": "thesis", "collection_id": "85", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01092007-104956", "primary_object_url": { "basename": "Kravaris_c_1984.pdf", "content": "final", "filesize": 7270039, "license": "other", "mime_type": "application/pdf", "url": "/85/1/Kravaris_c_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Identification of Spatially-Varying Parameters in Distributed Parameter Systems", "author": [ { "family_name": "Kravaris", "given_name": "Constantine (Costas)", "orcid": "0000-0003-0951-9493", "clpid": "Kravaris-Constantine-Costas" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Stephanopoulos", "given_name": "Gregory N.", "clpid": "Stephanopoulos-G-N" }, { "family_name": "Caughey", "given_name": "Thomas Kirk", "clpid": "Caughey-T-K" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Identification of spatially-varying parameters in distributed parameter systems given an observation of the state is as a rule an ill-posed problem in the sense of Hadamard. Even in case when the solution is unique, it does not depend continuously on the data. The identification problem that motivated this work arises in the description of petroleum reservoirs and subsurface aquifers; it consists of identifying the spatially-varying parameter \u03b1(x,y) in the diffusion equation ut = (\u03b1ux)x + (\u03b1uy)y + f given an observation of u at a discrete set of spatial locations.
\r\n\r\nThe question of uniqueness of \u03b1 (identifiability problem) is first investigated. The analysis is restricted to the one-dimensional version of the above equation i.e. to ut = (\u03b1ux)x + f and an observation of u at a single point. The identifiability problem is formulated as an inverse Sturm-Liouville problem for (\u03b1y')' + \u03bby = 0. It is proved that the eigenvalues and the normalizing constants determine the above Sturm-Liouville operator uniquely. Identifiability and non-identifiability results are obtained for three special cases.
\r\n\r\nThe problem of constructing stable approximate solutions to identification problems in distributed parameter systems is next investigated. The concept of regularization, widely used in solving linear Fredholm integral equations, is developed for the solution of such problems. A general regularization identification theory is presented and applied to the identification of parabolic systems. Two alternative numerical approaches for the minimization of the smoothing functional are investigated: (i) classical Banach space gradient methods and (ii) discretized minimization methods. The latter use finite-dimensional convergent approximations in Sobolev spaces and are based on an appropriate convergence theorem. The performance of the regularization identification method is evaluated by numerical experiments on the identification of spatially-varying diffusivity \u03b1 in the diffusion equation.
", "doi": "10.7907/m0kv-m285", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:4470", "collection": "thesis", "collection_id": "4470", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11092005-105529", "primary_object_url": { "basename": "Bassett_me_1984.pdf", "content": "final", "filesize": 6706054, "license": "other", "mime_type": "application/pdf", "url": "/4470/1/Bassett_me_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Mathematical Modeling of Atmospheric Aerosol Equilibria and Dynamics", "author": [ { "family_name": "Bassett", "given_name": "Mark Elliott", "clpid": "Bassett-Mark-Elliott" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Tschoegl", "given_name": "Nicholas W.", "clpid": "Tschoegl-N-W" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Atmospheric aerosols consist of submicron-sized particles occurring at number concentrations of the order of 105 cm-3 and mass concentrations of the order of 100 \u00b5g m-3. These aerosols, when occurring in urban areas, consist of aqueous solutions of sulfate, nitrate, ammonium, organic constituents, and certain metals. This thesis is a contribution toward our ability to describe mathematically the formation and growth of such atmospheric aerosols. Since a substantial fraction of the mass of urban aerosols consists of sulfate, nitrate, ammonium and water (Stelson and Seinfeld, 1981), the description of the dynamics of such an aerosol is an important place to initiate the development of aerosol models. The size and composition distribution of atmospheric aerosols are governed by a combination of thermodynamics and kinetics. A detailed treatment of the thermodynamics of the atmospheric sulfate/nitrate/ammonium/water system is presented. Based on this treatment, models are developed to predict the equilibrium quantity, composition, state, and size of the aerosol given gas phase properties. Aerosol kinetics are approached by solution of the General Dynamic Equation for the aerosol sized distribution using the sectional method of Gelbard and Seinfeld. In the most general kinetic model presented, the evolution of the size and composition of an atmospheric sulfate aerosol is predicted under power plant plume conditions. Users manuals for the computer codes comprising the models developed here are given in the Appendix.
", "doi": "10.7907/9mvc-2t06", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:4470", "collection": "thesis", "collection_id": "4470", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11092005-105529", "primary_object_url": { "basename": "Bassett_me_1984.pdf", "content": "final", "filesize": 6706054, "license": "other", "mime_type": "application/pdf", "url": "/4470/1/Bassett_me_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Mathematical Modeling of Atmospheric Aerosol Equilibria and Dynamics", "author": [ { "family_name": "Bassett", "given_name": "Mark Elliott", "clpid": "Bassett-Mark-Elliott" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Tschoegl", "given_name": "Nicholas W.", "clpid": "Tschoegl-N-W" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Atmospheric aerosols consist of submicron-sized particles occurring at number concentrations of the order of 105 cm-3 and mass concentrations of the order of 100 \u00b5g m-3. These aerosols, when occurring in urban areas, consist of aqueous solutions of sulfate, nitrate, ammonium, organic constituents, and certain metals. This thesis is a contribution toward our ability to describe mathematically the formation and growth of such atmospheric aerosols. Since a substantial fraction of the mass of urban aerosols consists of sulfate, nitrate, ammonium and water (Stelson and Seinfeld, 1981), the description of the dynamics of such an aerosol is an important place to initiate the development of aerosol models. The size and composition distribution of atmospheric aerosols are governed by a combination of thermodynamics and kinetics. A detailed treatment of the thermodynamics of the atmospheric sulfate/nitrate/ammonium/water system is presented. Based on this treatment, models are developed to predict the equilibrium quantity, composition, state, and size of the aerosol given gas phase properties. Aerosol kinetics are approached by solution of the General Dynamic Equation for the aerosol sized distribution using the sectional method of Gelbard and Seinfeld. In the most general kinetic model presented, the evolution of the size and composition of an atmospheric sulfate aerosol is predicted under power plant plume conditions. Users manuals for the computer codes comprising the models developed here are given in the Appendix.
", "doi": "10.7907/9mvc-2t06", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:4472", "collection": "thesis", "collection_id": "4472", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11092005-142825", "primary_object_url": { "basename": "Alam_mk_1984.pdf", "content": "final", "filesize": 3689701, "license": "other", "mime_type": "application/pdf", "url": "/4472/1/Alam_mk_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Nucleation and Condensational Growth of Aerosols: Application to Silicon Production", "author": [ { "family_name": "Alam", "given_name": "Md. Khairul", "clpid": "Alam-Md-Khairul" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Sabersky", "given_name": "Rolf H.", "clpid": "Sabersky-R-H" }, { "family_name": "Zukoski", "given_name": "Edward E.", "clpid": "Zukoski-E-E" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A theoretical analysis of aerosol nucleation and condensational growth is developed. A growing aerosol depletes the surrounding vapor, leading to the development of a spherically symmetric radial distribution of monomer partial pressure. A symmetric radial temperature profile is simultaneously developed due to release of latent heat of condensation. These local perturbations are analyzed to determine the total effect on the nucleation rate. The analysis forms the basis for building an experimental reactor for production of large particles of silicon for semiconductors and photovoltaic cells. The large size of the silicon particles facilitates separation and processing of the product.
", "doi": "10.7907/t1x1-p304", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:4472", "collection": "thesis", "collection_id": "4472", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11092005-142825", "primary_object_url": { "basename": "Alam_mk_1984.pdf", "content": "final", "filesize": 3689701, "license": "other", "mime_type": "application/pdf", "url": "/4472/1/Alam_mk_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Nucleation and Condensational Growth of Aerosols: Application to Silicon Production", "author": [ { "family_name": "Alam", "given_name": "Md. Khairul", "clpid": "Alam-Md-Khairul" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Sabersky", "given_name": "Rolf H.", "clpid": "Sabersky-R-H" }, { "family_name": "Zukoski", "given_name": "Edward E.", "clpid": "Zukoski-E-E" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A theoretical analysis of aerosol nucleation and condensational growth is developed. A growing aerosol depletes the surrounding vapor, leading to the development of a spherically symmetric radial distribution of monomer partial pressure. A symmetric radial temperature profile is simultaneously developed due to release of latent heat of condensation. These local perturbations are analyzed to determine the total effect on the nucleation rate. The analysis forms the basis for building an experimental reactor for production of large particles of silicon for semiconductors and photovoltaic cells. The large size of the silicon particles facilitates separation and processing of the product.
", "doi": "10.7907/t1x1-p304", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:3353", "collection": "thesis", "collection_id": "3353", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-080949", "primary_object_url": { "basename": "Pesthy_aj_1983.pdf", "content": "final", "filesize": 9245975, "license": "other", "mime_type": "application/pdf", "url": "/3353/1/Pesthy_aj_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Aerosol Formation and Growth in Laminar Flow", "author": [ { "family_name": "Pesthy", "given_name": "Andrew John", "clpid": "Pesthy-Andrew-John" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A detailed theoretical analysis of aerosol nucleation and growth in laminar flow, including the important aspects of mass and energy transfer and aerosol size distribution dynamics, is presented. Simulations of dibutyl phthalate aerosol formation and growth in a laminar flow cooled tube, in the presence and absence of seed particles, are carried out using the classical and Lothe-Pound theories of homogeneous nucleation. The competition between new particle formation and vapor growth onto seed particles is explored in detail. The mathematical model is compared to experimental measurements of aerosol volume distribution and dibutyl phthalate mass balance for a laminar flow cooled tube without seed particles. The model with Lothe-Pound theory shows fair agreement with the mass balance data, but over-predicts the total aerosol number concentration by four orders of magnitude.
", "doi": "10.7907/X6ZW-RA12", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3353", "collection": "thesis", "collection_id": "3353", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-080949", "primary_object_url": { "basename": "Pesthy_aj_1983.pdf", "content": "final", "filesize": 9245975, "license": "other", "mime_type": "application/pdf", "url": "/3353/1/Pesthy_aj_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Aerosol Formation and Growth in Laminar Flow", "author": [ { "family_name": "Pesthy", "given_name": "Andrew John", "clpid": "Pesthy-Andrew-John" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A detailed theoretical analysis of aerosol nucleation and growth in laminar flow, including the important aspects of mass and energy transfer and aerosol size distribution dynamics, is presented. Simulations of dibutyl phthalate aerosol formation and growth in a laminar flow cooled tube, in the presence and absence of seed particles, are carried out using the classical and Lothe-Pound theories of homogeneous nucleation. The competition between new particle formation and vapor growth onto seed particles is explored in detail. The mathematical model is compared to experimental measurements of aerosol volume distribution and dibutyl phthalate mass balance for a laminar flow cooled tube without seed particles. The model with Lothe-Pound theory shows fair agreement with the mass balance data, but over-predicts the total aerosol number concentration by four orders of magnitude.
", "doi": "10.7907/X6ZW-RA12", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3500", "collection": "thesis", "collection_id": "3500", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09122006-145635", "type": "thesis", "title": "Aerosol Deposition, Growth, and Dynamics in the Continuous Stirred Tank Reactor", "author": [ { "family_name": "Crump", "given_name": "James Gleason, III", "clpid": "Crump-James-Gleason-III" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Stephanopoulos", "given_name": "Gregory N.", "clpid": "Stephanopoulos-G-N" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Gelbard", "given_name": "Fred M.", "clpid": "Gelbard-Fred-M" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This work examines three related topics in aerosol science. First, a continuous stirred tank reactor (CSTR) for studying the dynamics of chemically reacting aerosol systems is described. This apparatus is designed to allow aerosols to react under conditions of controlled temperature and relative humidity and is applied to the study of growth of aqueous manganese sulfate aerosols in a humid atmosphere containing sulfur dioxide. From experimental data the rate of conversion of sulfur dioxide to sulfuric acid in manganese sulfate aerosols is deduced.
\r\n\r\nSecond, a new algorithm for inversion of aerosol size distribution data is presented. This algorithm is well suited to the ill-posed nature of the data inversion problem and is shown to give results superior to those obtained using conventional methods. This inversion technique is applied to the analysis of aerosol growth data.
\r\n\r\nFinally, the general steady state coagulation equations with particle sources and sinks are examined and shown to admit physically unrealistic solutions in some cases. General conditions are then given which insure the existence of physically acceptable solutions and these solutions are shown to have large particle tails that decay exponentially.
", "doi": "10.7907/yd9e-2s32", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3500", "collection": "thesis", "collection_id": "3500", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09122006-145635", "type": "thesis", "title": "Aerosol Deposition, Growth, and Dynamics in the Continuous Stirred Tank Reactor", "author": [ { "family_name": "Crump", "given_name": "James Gleason, III", "clpid": "Crump-James-Gleason-III" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Stephanopoulos", "given_name": "Gregory N.", "clpid": "Stephanopoulos-G-N" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Gelbard", "given_name": "Fred M.", "clpid": "Gelbard-Fred-M" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This work examines three related topics in aerosol science. First, a continuous stirred tank reactor (CSTR) for studying the dynamics of chemically reacting aerosol systems is described. This apparatus is designed to allow aerosols to react under conditions of controlled temperature and relative humidity and is applied to the study of growth of aqueous manganese sulfate aerosols in a humid atmosphere containing sulfur dioxide. From experimental data the rate of conversion of sulfur dioxide to sulfuric acid in manganese sulfate aerosols is deduced.
\r\n\r\nSecond, a new algorithm for inversion of aerosol size distribution data is presented. This algorithm is well suited to the ill-posed nature of the data inversion problem and is shown to give results superior to those obtained using conventional methods. This inversion technique is applied to the analysis of aerosol growth data.
\r\n\r\nFinally, the general steady state coagulation equations with particle sources and sinks are examined and shown to admit physically unrealistic solutions in some cases. General conditions are then given which insure the existence of physically acceptable solutions and these solutions are shown to have large particle tails that decay exponentially.
", "doi": "10.7907/yd9e-2s32", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3293", "collection": "thesis", "collection_id": "3293", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08312006-082647", "type": "thesis", "title": "Modeling the Reactions of Coal Liquids", "author": [ { "family_name": "Allen", "given_name": "David Thomas", "orcid": "0000-0001-6646-8755", "clpid": "Allen-David-Thomas" } ], "thesis_advisor": [ { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" } ], "thesis_committee": [ { "family_name": "Gavalas", "given_name": "George R.", "orcid": "0000-0003-1468-6835", "clpid": "Gavalas-G-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis begins the development of a new approach to the kinetic modeling of complex hydrocarbon mixtures. The approach is based on functional group reactions and its implementation involves three steps. The first step is to characterize complex hydrocarbon mixtures, such as coal-derived liquids, heavy oils and shale oils, in terms of their constituent functional groups. A methodology is defined for estimating functional group concentrations from elemental analysis and NMR data. Mass spectra, infared spectra, separation yields and other analytical data may also be incorporated into the concentration estimates. The methodology is demonstrated for a heavy oil and for a wide variety of coal liquids.
\r\n\r\nThe concentrations provide a starting point for kinetic modeling. The second step of the modeling procedure is to determine the rates and pathways of the reactions of the functional groups by investigating the reactions of pure compounds containing the same functionalities. The reactions of a number of these model compound systems were examined. The studies focused on the reactions of atomic hydrogen under conditions appropriate to coal liquefaction.
\r\n\r\nThe final step in the modeling is the development of a mathematical model which can predict changes in functional group concentrations given initial concentrations and reaction rates. This is outside the scope of this thesis, but general guidelines and valid simplifications are discussed.
\r\n", "doi": "10.7907/ph4t-rb90", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3359", "collection": "thesis", "collection_id": "3359", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-113244", "type": "thesis", "title": "Thermodynamics of Aqueous Atmospheric Aerosols", "author": [ { "family_name": "Stelson", "given_name": "Arthur Wesley", "clpid": "Stelson-Arthur-Wesley" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Morgan", "given_name": "James J.", "clpid": "Morgan-J-J" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "A novel application of classical thermodynamics is presented to understand the distribution of aerosol forming material between the gas and aerosol phases in the polluted troposphere. The particular system studied involves NH4NO3 and its interactions with the environmental variables, temperature, relative humidity, droplet pH and aqueous (NH4)2SO4 concentration. In Chapter 1, the theoretical temperature dependence of the solid NH4NO3 dissociation constant is compared to ambient ammonia-nitric acid partial pressure products and general agreement is shown. Also, temperature is demonstrated to be a determining factor for ambient aerosol nitrate formation. Chapter 2 discusses how an urban aerosol can be chemically characterized and that the aqueous electrolytic aerosol solutions are very concentrated (> 8 molal). Thus, any attempt to model ion interactions in aerosol solutions must be able to represent the concentrated solution regime. The ammonia-nitric acid partial pressure product for concentrated NH4NO3-HNO3-H2O solutions is shown to be sensitive to relative humidity but not to pH (1-7) in Chapter 3. Since the ammonia-nitric acid partial pressure product is insensitive to pH, the NH4NO3 dissociation constant over NH4NO3-H2O solutions should typify the ammonia-nitric acid partial pressure product above slightly acidic solutions. The NH4NO3 dissociation constant temperature and relative humidity dependence is evaluated and compared to ambient data in Chapter 4. General agreement between the predictions and the data exists but the possible effect of additional solutes in aerosol droplets is evident. Since NH4NO3 and (NH4)2SO4 are present in atmospheric particles of similar size, it is appropriate to calculate the effect of (NH4)2SO4 on the relative humidity dependence of the NH4NO3 dissociation constant. Chapter 5 shows the presence of (NH4)2SO4 reduces the amount of ammonia and nitric acid in the gas phase and that the NH4NO3 dissociation constant is only 40% less for a 0.5 (NH4)2SO4 ionic strength fraction in aqueous solution. Also, methods for predicting the particle growth, the solution density and the refractive index of NH4NO3-(NH4)2SO4-H2O solutions are outlined in Chapter 5. Good accordance between experimental data and predictions is demonstrated indicating the possible applicability of these techniques to more complex multicomponent solutions.
\r\n\r\nIn the Appendices, a density prediction technique for (NH4)2SO4-H2SO4-H2O solutions is presented since this aspect of ambient aerosols is not contained in the major thrust of this work.
", "doi": "10.7907/m9ac-pe87", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:5109", "collection": "thesis", "collection_id": "5109", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12212006-103605", "type": "thesis", "title": "Investigations of Transport in Complex Atmospheric Flow Systems: I. Small Scale Studies of Diffusion through Porous Media, Impact of Fumehood Exhaust Reentry on Indoor Air Quality, and Pollutant Transport Near an Isolated Island. II. Pollutant Transport in Mountain-Valley and Coastal Regions of California", "author": [ { "family_name": "Reible", "given_name": "Danny David", "clpid": "Reible-Danny-David" } ], "thesis_advisor": [ { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" } ], "thesis_committee": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" }, { "family_name": "Cass", "given_name": "Glen Rowan", "clpid": "Cass-G-R" }, { "family_name": "Roshko", "given_name": "Anatol", "clpid": "Roshko-A" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis details some applications of tracer techniques from laboratory scale studies of diffusion in porous media to the analysis of the transport and dispersion of pollutants in the mountain-valley and coastal environments that form the majority of the state of California.
\r\n\r\nChapter 1 describes a technique for estimating gaseous diffusivities in porous media that is based on the general solution to Fick's second law for diffusion in a tube between two well-mixed volumes. In beds of essentially non-porous particles, the ratio of the measured effective diffusivity to the air diffusivity of a gas was found to be proportional to the bed porosity raised to the 1.43 power, a result in agreement with previous studies on similar materials. High moisture content (>15-20% moisture in sand) was found to significantly reduce the gas diffusivity with respect to that found in dry materials.
\r\n\r\nChapter 2 indicates the importance of ventilation system imbalance upon the reentrainment of pollutants exhausted from a building. Tracer was released from a fumehood in a \"clean\" room at the Jet Propulsion Laboratory. Indoor concentrations as high as 235 PPB/gr-mole tracer released/hr were observed due to infiltration of the exhausted tracer. This concentration is about an order of magnitude higher than has been observed in buildings with more balanced ventilation systems. Predictions of single and multi-compartment stirred-tank models were compared to the dynamics of the tracer infiltration. A simple one-compartment model provided a better description of the infiltration dynamics than a three-compartment model suggested by the design of the ventilation system.
\r\n\r\nChapter 3 describes a series of atmospheric tracer studies of the transport and dispersion of pollutants over the ocean and near an isolated island cape. The experiments were designed to determine the impact of local sources on a background air quality sampling program. The horizontal dispersion of the tracer over the ocean surface could be approximated by the Gaussian plume model assuming a neutrally stable atmosphere, in general agreement with the expected atmospheric stability. Tracer releases from the surface of the isolated cape indicated that an essentially well-mixed separated zone existed above and downwind of the cape. The height of this zone extended to 35-40% above the height of the cape, about the same height as the wake downwind of an isolated building. Limited mixing between the separated zone and the freestream resulted in a sharp concentration gradient above this height.
\r\n\r\nChapter 5 indicates the difficulties of describing the behavior of pollutants in complex terrain. A series of tracer experiments conducted in the northern and central California Coastal Mountains are described. The Gaussian plume model could be used to describe the dispersion of the tracer during strong, unidirectional winds. During an elevated tracer release, however, wind directional shear with altitude led to plume bifurcation, with the majority being transported through a stable nighttime drainage layer to ground level. The transport through the stable layer occurred at a vertical velocity of about 2 cm/s, surprisingly rapid transport between stably stratified layers of the atmosphere.
\r\n\r\nChapter 6 describes the uncertainties associated with mass balance and Gaussian parameter estimates from tracer data. The uncertainty in the calculated final result can be less than the errors (assumed random) associated with any individual experimental measurement, indicating that such calculations can be made with greater accuracy than would initially be expected.
\r\n\r\nChapter 7 details the transport of pollutants in the San Joaquin Valley during stable wintertime conditions. The relatively limited net ventilation of the valley indicates that pollutants can remain within the valley for several days subsequent to their release. During one tracer experiment, about 50% of the released tracer was observed to be well-mixed within the southern valley about 72 hours after the beginning of the release. The most significant ventilation mechanism for the valley during the winter was the occasional passage of low pressure frontal systems. Long periods without frontal system passage can lead to significant pollutant buildup.
\r\n\r\nChapter 8 describes the transport of pollutants in the San Joaquin Valley during summertime conditions. While much more effectively ventilated than during the winter, the increased solar insolation leads to significant ozone levels within the valley. A strong influx of air at the northern mouth of the valley is balanced during the day by a corresponding efflux at its southern end and by daytime upslope flow on the Sierra Nevada Mountains. At night, an eddy forms in the southern valley due to low level stabilization and terrain blockage of the afternoon efflux over the southern boundary of the valley. This eddy grows as more air is entrained from the influx at the northern mouth of the valley. An accelerated layer of air aloft also develops during the night due to surface layer stabilization and decoupling. These dynamic flow structures are significant factors in the transport and dispersion of pollutants in the valley during the summer.
\r\n\r\nChapter 9 details the impact of the San Joaquin Valley on the northern Mojave Desert. The transport of pollutants from the southern valley was linked through both tracer and aerosol data to the rapid nighttime reduction in visibility in the northern Mojave Desert. Unlike winter conditions, most of the pollutants in the southern valley were transported out of the valley within a day after their release.
\r\n\r\nChapter 10 describes the impact on the Sierra Nevada Mountains of pollutant sources within the San Joaquin Valley. Tracer released within the valley was efficiently transported upslope, impacting National Park and Forest areas. The maximum concentrations observed upslope could be approximated with the Gaussian plume model, assuming very unstable atmospheric conditions. Nighttime stabilization arrested the upslope movement of the tracer and led to slope and valley impacts throughout the night. The limited nighttime ventilation of the slopes may result in the significant ozone concentrations typically observed at slope sites throughout the night.
\r\n\r\nChapter 11 describes the transport characteristics of the Sacramento Valley, the northern half of the California Central Valley. Tracer experiments indicated that San Francisco Bay area pollutants have only a small effect on the air quality in the Sacramento Valley. A midday flow divergence over Sacramento resulted in tracer impacts in both the northern part of the valley and the slopes northeast of the city. A counterclockwise eddy that forms in the southern valley during the morning was a potential mechanism for recirculating aged pollutants within the valley. During one tracer experiment, most of the released tracer was trapped within an elevated layer of air, a potentially important mechanism for multi-day impacts of pollutants.
\r\n\r\nChapter 12 evaluates the transport of pollutants in the Santa Barbara Channel off the coast of southern California. Limited vertical mixing combined with diurnal wind reversals resulted in multi-day onshore impacts of the tracer released offshore. Efficient lateral mixing of the tracer during wind reversals led to a widespread coastal impact from a single point source. The existence of many point sources could result in a diluted background concentration (i.e. after wind reversals) that equals or exceeds the concentration directly downwind of a single source.
\r\n\r\nChapter 13 develops a two layer model of the atmosphere that semi-quantitatively incorporates much of the basic transport structure observed in the above studies. The method of characteristics and the method of moments were used to examine the implications of the model. The model indicates that the air aloft must be considered in order to accurately predict the impact of a pollutant source, especially when considering the multi-day or long range impact of the source.
", "doi": "10.7907/X6WE-JD66", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:1609", "collection": "thesis", "collection_id": "1609", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05042006-134537", "type": "thesis", "title": "Mathematical Modeling of Photochemical Air Pollution", "author": [ { "family_name": "McRae", "given_name": "Gregory John", "clpid": "McRae-Gregory-John" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Kreiss", "given_name": "Heinz-Otto", "clpid": "Kreiss-H-O" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Holmes", "given_name": "John R.", "clpid": "Holmes-John-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Air pollution is an environmental problem that is both pervasive and difficult to control. An important element of any rational control approach is a reliable means for evaluating the air quality impact of alternative abatement measures. This work presents such a capability, in the form of a mathematical description of the production and transport of photochemical oxidants within an urban airshed. The combined influences of advection, turbulent diffusion, chemical reaction, emissions and surface removal processes are all incorporated into a series of models that are based on the species continuity equations. A delineation of the essential assumptions underlying the formulation of a three-dimensional, a Lagrangian trajectory, a vertically integrated and single cell air quality model is presented. Since each model employs common components and input data the simpler forms can be used for rapid screening calculations and the more complex ones for detailed evaluations.
\r\n\r\nThe flow fields, needed for species transport, are constructed using inverse distance weighted polynomial interpolation techniques that map routine monitoring data onto a regular computational mesh. Variational analysis procedures are then employed to adjust the field so that mass is conserved. Initial concentration and mixing height distributions can be established with the same interpolation algorithms.
\r\n\r\nSubgrid scale turbulent transport is characterized by a gradient diffusion hypothesis. Similarity solutions are used to model the surface layer fluxes. Above this layer different treatments of turbulent diffusivity are required to account for variations in atmospheric stability. Convective velocity scaling is utilized to develop eddy diffusivities for unstable conditions. The predicted mixing times are in accord with results obtained during sulfur hexafluoride (SF6) tracer experiments. Conventional models are employed for neutral and stable conditions.
\r\n\r\nA new formulation for gaseous deposition fluxes is presented that provides a means for estimating removal rates as a function of atmospheric stability. The model satisfactorily reproduces measured deposition velocities for reactive materials. In addition it is shown how computational cell size influences the representation of surface removal.
\r\n\r\nChemical interactions between twenty nine chemical species are described by a 52 step kinetic mechanism. The atmospheric hydrocarbon chemistry is modeled by the reactions of six lumped classes: alkanes, ethylene, other olefins, aromatics, formaldehyde and other aldehydes; a grouping that enables representation of a wide range of smog chamber experiments and atmospheric conditions. Chemical lumping minimizes the number of species while maintaining a high degree of detail for the inorganic reactions. Variations in rate data, stoichiometric coefficients and initial conditions have been studied using the Fourier Amplitude Sensitivity Test.
\r\n\r\nThe wide variation in time scales, non-linearity of the chemistry and differences in transport processes complicates selection of numerical algorithms. Operator splitting techniques are used to decompose the governing equation into elemental steps of transport and chemistry. Each transport operator is further split into advective and diffusive components so that linear finite element and compact finite difference schemes can be applied to their best advantage. Because most of the computer time is consumed by the chemical kinetics those species that could be accurately described by pseudo-steady state approximations were identified reducing the number of species, described by differential equations, to 15.
\r\n\r\nWhile the mathematical formulation of the complete system contains no regional or area specific information, performance evaluation studies were carried out using data measured in the South Coast Air Basin of Southern California. Detailed emissions and meteorological information were assembled for the period 26-28 June 1974. A comparison between predictions and observed air quality, during multi-day periods, indicates that the model can satisfactorily describe urban scale atmospheric concentration dynamics.
", "doi": "10.7907/n8p7-f149", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:1609", "collection": "thesis", "collection_id": "1609", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05042006-134537", "type": "thesis", "title": "Mathematical Modeling of Photochemical Air Pollution", "author": [ { "family_name": "McRae", "given_name": "Gregory John", "clpid": "McRae-Gregory-John" } ], "thesis_advisor": [ { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "thesis_committee": [ { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Kreiss", "given_name": "Heinz-Otto", "clpid": "Kreiss-H-O" }, { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Holmes", "given_name": "John R.", "clpid": "Holmes-John-R" }, { "family_name": "Seinfeld", "given_name": "John H.", "orcid": "0000-0003-1344-4068", "clpid": "Seinfeld-J-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Air pollution is an environmental problem that is both pervasive and difficult to control. An important element of any rational control approach is a reliable means for evaluating the air quality impact of alternative abatement measures. This work presents such a capability, in the form of a mathematical description of the production and transport of photochemical oxidants within an urban airshed. The combined influences of advection, turbulent diffusion, chemical reaction, emissions and surface removal processes are all incorporated into a series of models that are based on the species continuity equations. A delineation of the essential assumptions underlying the formulation of a three-dimensional, a Lagrangian trajectory, a vertically integrated and single cell air quality model is presented. Since each model employs common components and input data the simpler forms can be used for rapid screening calculations and the more complex ones for detailed evaluations.
\r\n\r\nThe flow fields, needed for species transport, are constructed using inverse distance weighted polynomial interpolation techniques that map routine monitoring data onto a regular computational mesh. Variational analysis procedures are then employed to adjust the field so that mass is conserved. Initial concentration and mixing height distributions can be established with the same interpolation algorithms.
\r\n\r\nSubgrid scale turbulent transport is characterized by a gradient diffusion hypothesis. Similarity solutions are used to model the surface layer fluxes. Above this layer different treatments of turbulent diffusivity are required to account for variations in atmospheric stability. Convective velocity scaling is utilized to develop eddy diffusivities for unstable conditions. The predicted mixing times are in accord with results obtained during sulfur hexafluoride (SF6) tracer experiments. Conventional models are employed for neutral and stable conditions.
\r\n\r\nA new formulation for gaseous deposition fluxes is presented that provides a means for estimating removal rates as a function of atmospheric stability. The model satisfactorily reproduces measured deposition velocities for reactive materials. In addition it is shown how computational cell size influences the representation of surface removal.
\r\n\r\nChemical interactions between twenty nine chemical species are described by a 52 step kinetic mechanism. The atmospheric hydrocarbon chemistry is modeled by the reactions of six lumped classes: alkanes, ethylene, other olefins, aromatics, formaldehyde and other aldehydes; a grouping that enables representation of a wide range of smog chamber experiments and atmospheric conditions. Chemical lumping minimizes the number of species while maintaining a high degree of detail for the inorganic reactions. Variations in rate data, stoichiometric coefficients and initial conditions have been studied using the Fourier Amplitude Sensitivity Test.
\r\n\r\nThe wide variation in time scales, non-linearity of the chemistry and differences in transport processes complicates selection of numerical algorithms. Operator splitting techniques are used to decompose the governing equation into elemental steps of transport and chemistry. Each transport operator is further split into advective and diffusive components so that linear finite element and compact finite difference schemes can be applied to their best advantage. Because most of the computer time is consumed by the chemical kinetics those species that could be accurately described by pseudo-steady state approximations were identified reducing the number of species, described by differential equations, to 15.
\r\n\r\nWhile the mathematical formulation of the complete system contains no regional or area specific information, performance evaluation studies were carried out using data measured in the South Coast Air Basin of Southern California. Detailed emissions and meteorological information were assembled for the period 26-28 June 1974. A comparison between predictions and observed air quality, during multi-day periods, indicates that the model can satisfactorily describe urban scale atmospheric concentration dynamics.
", "doi": "10.7907/n8p7-f149", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" } ]