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Determination Of Secondary Organic Aerosol Sources Precursors And Properties Using Novel Measurement And Modeling Techniques
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Book Synopsis Determination of Secondary Organic Aerosol Sources, Precursors, and Properties Using Novel Measurement and Modeling Techniques by : Giulia Stefenelli
Download or read book Determination of Secondary Organic Aerosol Sources, Precursors, and Properties Using Novel Measurement and Modeling Techniques written by Giulia Stefenelli and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Establishing Chemical Mechanisms and Estimating Phase State of Secondary Organic Aerosol From Atmospherically Relevant Organic Precursors by : Shashank Jain
Download or read book Establishing Chemical Mechanisms and Estimating Phase State of Secondary Organic Aerosol From Atmospherically Relevant Organic Precursors written by Shashank Jain and published by . This book was released on 2016 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic aerosol (OA) is a ubiquitous component of atmospheric particulate that influences both human health and global climate. A large fraction of OA is secondary in nature (SOA), being produced by oxidation of volatile organic compounds (VOCs) emitted by biogenic and anthropogenic sources. Despite the integral role of SOA in atmospheric processes, there remains a limited scientific understanding of the chemical and physical changes induced in SOA as it ages in the atmosphere. This thesis describes work done to increase the knowledge of processes and properties of atmospherically relevant SOA. In the work presented in this thesis, I have worked on improving an existing innovative, soft ionization aerosol mass spectrometer and utilized it to establish chemical mechanisms for oxidation of atmospherically relevant organic precursors (i.e., Green Leaf Volatiles). I discovered that SOA formation from cis-3-hexen-1-ol is dominated by oligomer and higher molecular weight products, whereas the acetate functionality in cis-3-hexenylacetate inhibited oligomer formation, resulting in SOA that is dominated by low molecular weight products. One of the most important factors contributing to uncertainties in our estimations of SOA mass in the atmosphere, remains our basic assumption that atmospheric SOA is liquid-like, which we have found to be untrue. Hence, I developed a methodology to estimate the phase state of SOA and identified new parameters that can have significant influence on the phase state of atmospheric aerosol. This simplified method eliminates the need for a Scanning Mobility Particle Sizer (SMPS) and directly measures Bounce Factor (BF) of polydisperse SOA using only one multi-stage cascade Electrostatic Low Pressure Impactor (ELPI). The novel method allows for the real time determination of SOA phase state, permitting studies of the relationship between SOA phase, oxidative formation and chemical aging in the atmosphere. I demonstrated that SOA mass loading (CSOA) influences the phase state significantly. Results show that under nominally identical conditions, the maximum BF decreases by approximately 30% at higher CSOA and suggests that extrapolation of experiments not conducted at atmospherically relevant SOA levels to simulate the chemical properties may not yield results that are relevant to our natural environment. My work has provided a better understanding of the mechanisms of aerosol formation at atmospheric concentrations, which is necessary to understand its physical properties. This improved understanding is fundamental to accurately model aerosol formation in the atmosphere, and subsequently evaluate their large-scale effect on human health and environment.
Book Synopsis Evaluation of New and Proposed Organic Aerosol Sources and Mechanisms Using the Aerosol Modeling Testbed by :
Download or read book Evaluation of New and Proposed Organic Aerosol Sources and Mechanisms Using the Aerosol Modeling Testbed written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work investigated the formation and evolution of organic aerosols (OA) arising from anthropogenic and biogenic sources in a framework that combined state-of-the-science process and regional modeling, and their evaluation against advanced and emerging field measurements. Although OA are the dominant constituents of submicron particles, our understanding of their atmospheric lifecycle is limited, and current models fail to describe the observed amounts and properties of chemically formed secondary organic aerosols (SOA), leaving large uncertainties on the effects of SOA on climate. Our work has provided novel modeling constraints on sources, formation, aging and removal of SOA by investigating in particular (i) the contribution of trash burning emissions to OA levels in a megacity, (ii) the contribution of glyoxal to SOA formation in aqueous particles in California during CARES/CalNex and over the continental U.S., (iii) SOA formation and regional growth over a pine forest in Colorado and its sensitivity to anthropogenic NOx levels during BEACHON, and the sensitivity of SOA to (iv) the sunlight exposure during its atmospheric lifetime, and to (v) changes in solubility and removal of organic vapors in the urban plume (MILAGRO, Mexico City), and over the continental U.S. We have also developed a parameterization of water solubility for condensable organic gases produced from major anthropogenic and biogenic precursors based on explicit chemical modeling, and made it available to the wider community. This work used for the first time constraints from the explicit model GECKO-A to improve SOA representation in 3D regional models such as WRF-Chem.
Book Synopsis Enabling the Identification, Quantification, and Characterization of Organics in Complex Mixtures to Understand Atmospheric Aerosols by : Gabriel Avram Isaacman
Download or read book Enabling the Identification, Quantification, and Characterization of Organics in Complex Mixtures to Understand Atmospheric Aerosols written by Gabriel Avram Isaacman and published by . This book was released on 2014 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: Particles in the atmosphere are known to have negative health effects and important but highly uncertain impacts on global and regional climate. A majority of this particulate matter is formed through atmospheric oxidation of naturally and anthropogenically emitted gases to yield highly oxygenated secondary organic aerosol (SOA), an amalgamation of thousands of individual chemical compounds. However, comprehensive analysis of SOA composition has been stymied by its complexity and lack of available measurement techniques. In this work, novel instrumentation, analysis methods, and conceptual frameworks are introduced for chemically characterizing atmospherically relevant mixtures and ambient aerosols, providing a fundamentally new level of detailed knowledge on their structures, chemical properties, and identification of their components. This chemical information is used to gain insights into the formation, transformation and oxidation of organic aerosols. Biogenic and anthropogenic mixtures are observed in this work to yield incredible complexity upon oxidation, producing over 100 separable compounds from a single precursor. As a first step toward unraveling this complexity, a method was developed for measuring the polarity and volatility of individual compounds in a complex mixture using two-dimensional gas chromatography, which is demonstrated in Chapter 2 for describing the oxidation of SOA formed from a biogenic compound (longifolene: C15H24). Several major products and tens of substantial minor products were produced, but none could be identified by traditional methods or have ever been isolated and studied in the laboratory. A major realization of this work was that soft ionization mass spectrometry could be used to identify the molecular mass and formula of these unidentified compounds, a major step toward a comprehensive description of complex mixtures. This was achieved by coupling gas chromatography to high resolution time-of-flight mass spectrometry with vacuum ultraviolet (VUV) photo-ionization. Chapters 3 and 4 describe this new analytical technique and its initial application to determine the structures of unknown compounds and formerly unresolvable mixtures, including a complete description of the chemical composition of two common petroleum products related to anthropogenic emissions: diesel fuel and motor oil. The distribution of hydrocarbon isomers in these mixtures - found to be mostly of branched, cyclic, and saturated - is described with unprecedented detail. Instead of measuring average bulk aerosol properties, the methods developed and applied in this work directly measure the polarity, volatility, and structure of individual components to allow a mechanistic understanding of oxidation processes. Novel characterizations of these complex mixtures are used to elucidate the role of structure and functionality in particle-phase oxidation, including in Chapter 4 the first measurements of relative reaction rates in a complex hydrocarbon particle. Molecular structure is observed to influence particle-phase oxidation in unexpected and important ways, with cyclization decreasing reaction rates by ~30% and branching increasing reaction rates by ~20-50%. The observed structural dependence is proposed to result in compositional changes in anthropogenic organic aerosol downwind of urban areas, which has been confirmed in subsequent work by applying the techniques described here. Measurement of organic aerosol components is extended to ambient environments through the development of instrumentation with the unprecedented capability to measure hourly concentrations and gas/particle partitioning of individual highly oxygenated organic compounds in the atmosphere. Chapters 5 and 6 describe development of new procedures and hardware for the calibration and analysis of oxygenates using the Semi-Volatile Thermal desorption Aerosol Gas chromatograph (SV-TAG), a custom instrument for in situ quantification of gas- and particle-phase organic compounds in the atmosphere. High time resolution measurement of oxygenated compounds is achieved through a reproducible and quantitative methodology for in situ "derivatization"--Replacing highly polar functional groups that cannot be analyzed by traditional gas chromatography with less polar groups. Implementation of a two-channel sampling system for the simultaneous collection of particle-phase and total gas-plus-particle phase samples allows for the first direct measurements of gas/particle partitioning in the atmosphere, significantly advancing the study of atmospheric composition and variability, as well as the processes governing condensation and re-volatilization. This work presents the first in situ measurements of a large suite of highly oxygenated biogenic oxidation products in both the gas- and particle-phase. Isoprene, the most ubiquitous biogenic emission, oxidizes to form 2-methyltetrols and C5 alkene triols, while [alpha]-pinene, the most common monoterpene, forms pinic, pinonic, hydroxyglutaric, and other acids. These compounds are reported in Chapter 7 with unprecedented time resolution and are shown for the first time to have a large gas-phase component, contrary to typical assumptions. Hourly comparisons of these products with anthropogenic aerosol components elucidate the interaction of human and natural emissions at two rural sites: the southeastern, U.S. and Amazonia, Brazil. Anthropogenic influence on SOA formation is proposed to occur through the increase in liquid water caused by anthropogenic sulfate. Furthermore, these unparalleled observations of gas/particle partitioning of biogenic oxidation products demonstrate that partitioning of oxygenates is unexpectedly independent of volatility: many volatile, highly oxygenated compounds have a large particle-phase component that is poorly described by traditional models. These novel conclusions are reached in part by applying the new frameworks developed in previous chapters to understand the properties of unidentified compounds, demonstrating the importance of detailed characterization of atmospheric organic mixtures. Comprehensive analysis of anthropogenic and biogenic emissions and oxidation product mixtures is coupled in this work with high time-resolution measurement of individual organic components to yield significant insights into the transformations of organic aerosols. Oxidation chemistry is observed in both laboratory and field settings to depend on molecular properties, volatility, and atmospheric composition. However, this work demonstrates that these complex processes can be understood through the quantification of individual known and unidentified compounds, combined with their classification into descriptive frameworks.
Book Synopsis Characterization of the Molecular Composition of Secondary Organic Aerosols Using High Resolution Mass Spectrometry by : Rachel Elizabeth Sellon
Download or read book Characterization of the Molecular Composition of Secondary Organic Aerosols Using High Resolution Mass Spectrometry written by Rachel Elizabeth Sellon and published by . This book was released on 2012 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric aerosols can affect visibility and the Earth's climate by scattering and absorbing light and they also can have adverse effects on human health. The organic portion of atmospheric aerosols is very complex and is a major fraction of fine particulate matter. High molecular weight (high-MW)/oligomeric organic compounds can make up a large part of this organic fraction and the composition, sources, and formation mechanisms for these compounds are not well understood. This knowledge and understanding is necessary to decrease the uncertainty in the climate affects of aerosols and to improve climate models. This dissertation investigates the composition and formation mechanisms for the high-MW/oligomeric fraction of secondary organic aerosols (SOA) collected in Bakersfield, CA and presents a comparative analysis of chamber and ambient SOA, from both Los Angeles (LA) and Bakersfield, to investigate sources at both locations. A novel sampling technique, nanospray-Desorption Electrospray Ionization (nano-DESI), was used with high resolution mass spectrometry (HR-MS) to determine the molecular formulas of the high molecular weight (HMW)/oligomeric fraction of SOA. Nano-DESI involves direct desorption from the sample surface and was used to limit reactions that can take place with extraction and storage in solvent. The samples were collected in Bakersfield and LA during CalNex 2010. Both Bakersfield and LA are out of compliance with EPA standards of ozone and particulate matter and provide opportunities to examine air masses affected by both anthropogenic and biogenic sources. This dissertation has provided the first evidence of observable changes in the composition of high-MW/oligomeric compounds throughout the day. Using positive mode nano-DESI, afternoon increases in the number of compounds that contain carbon, hydrogen and oxygen (CHO) were observed consistent with photochemistry/ozonolysis as a major source for these compounds. Compounds containing reduced nitrogen groups were dominant at night and had precursors consistent with imine formation products from the reaction of carbonyls and ammonia. In the negative mode, organonitrates (CHON) and nitroxy organosulfates (CHONS) had larger numbers of compounds in the night/morning samples consistent with nitrate radical formation reactions. A subset of the CHONS compounds and compounds containing sulfur (CHOS) had the same composition as known biogenic organosulfates and nitroxy organosulfates indicating contributions from both biogenic and anthropogenic sources to the SOA. This dissertation also provides the first analysis of the high-MW/oligomeric fraction in size resolved samples; the majority of the compounds were found in aerosol diameters between 0.18-1.0 micrometers and the CHON were bimodal with size. Finally, this dissertation presents the first comparative analysis of the overlap in the composition of this fraction of SOA between ambient and chamber samples. Samples collected in Pasadena, LA and Bakersfield were compared with samples collected in a smog chamber using diesel and isoprene sources. The results indicate that diesel had the highest overlap at both sites, Bakersfield samples were more oxidized, and LA showed evidence of a SOA plume arriving from downtown LA. The addition of ammonia to the diesel chamber experiment was necessary to form many of the 2N compounds found in Bakersfield. These results increase our understanding of the types of compounds found in urban environments and give evidence for the timescales of formation reactions in an ambient environment. They show that the majority of the high-MW oligomeric compounds are found in submicron size particles and that the composition of this fraction of SOA varies with aerosol size. Results from the chamber comparisons show that both diesel and isoprene are important sources for these compounds and also that there other sources are present. Future work that combines this type of analysis, in other ambient environments, with studies of the optical properties of aerosols could be used to help improve climate models and to start to close the gap in our understanding of the climate effects of atmospheric aerosols.
Book Synopsis Chemical Characterization and Source Apportionment of Atmospheric Aerosols in Urban and Rural Regions by : Caroline Parworth
Download or read book Chemical Characterization and Source Apportionment of Atmospheric Aerosols in Urban and Rural Regions written by Caroline Parworth and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerosols, or particulate matter (PM), can affect climate through scattering and absorption of radiation and influence the radiative properties, precipitation efficiency, thickness, and lifetime of clouds. Aerosols are one of the greatest sources of uncertainty in climate model predictions of radiative forcing. To fully understand the sources of uncertainty contributing to the radiative properties of aerosols, measurements of PM mass, composition, and size distribution are needed globally and seasonally. To add to the current understanding of the seasonal and temporal variations in aerosol composition and chemistry, this study has focused on the quantification, speciation, and characterization of atmospheric PM in urban and rural regions of the United States (US) for short and long periods of time. In the first two chapters, we focus on 1 month of aerosol and gas-phase measurements taken in Fresno, CA, an urban and agricultural area, during the National Aeronautics and Space Administration's (NASA) field study called DISCOVER-AQ. This air quality measurement supersite included a plethora of highly detailed chemical measurements of aerosols and gases, which were made at the same time as similar aircraft column measurements of aerosols and gases. The goal of DISCOVER-AQ is to improve the interpretation of satellite observations to approximate surface conditions relating to air quality, which can be achieved by making concurrent ground- and aircraft-based measurements of aerosols and gases. We begin in chapter 2 by exploring the urban aerosol and gas-phase dataset from the NASA DISCOVER-AQ study in California. Specifically, we discuss the chemical composition and mass concentration of water-soluble PM2.5 that were measured using a particle-into-liquid sampler with ion chromatography (PILS-IC) in Fresno, California from January 13–February 10, 2013. This data was analyzed for ionic inorganic species, organic acids and amines. Gas-phase species including HNO3 and NH3 were collected with annular denuders and analyzed using ion chromatography. Using the thermodynamic E-AIM model, inorganic particle water mass concentration and pH were calculated for the first time in this area. Organic particle water mass concentration was calculated from [kappa]-Köhler theory. In chapter 3 further analysis of the aerosol- and gas-phase data measured during DISCOVER-AQ was performed to determine the effectiveness of a local residential wood burning curtailment program in improving air quality. Using aerosol speciation and concentration measurements from the 2013 winter DISCOVER-AQ study in Fresno, CA, we investigate the impact of residential wood burning restrictions on fine particulate mass concentration and composition. Key species associated with biomass burning in this region include K+, acetonitrile, black carbon, and biomass burning organic aerosol (BBOA), which represents primary organic aerosol associated with residential wood burning. Reductions in acetonitrile associated with wood burning restrictions even at night were not observed and most likely associated with stagnant conditions during curtailment periods that led to the buildup of this long-lived gas. In chapter 4 we transition to the rural aerosol dataset from the DOE SGP site. We discuss the chemical composition and mass concentration of non-refractory submicron aerosols (NR-PM1) that were measured with an aerosol chemical speciation monitor (ACSM) at the DOE SGP site from November 2010 through June 2012. Positive matrix factorization (PMF) was performed on the measured organic aerosol (OA) mass spectral matrix using a newly developed rolling window technique to derive factors associated with distinct sources, evolution processes, and physiochemical properties. The rolling window approach captured the dynamic variations of the chemical properties of the OA factors over time. Three OA factors were obtained including two oxygenated OA (OOA) factors, differing in degrees of oxidation, and a BBOA factor. Sources of NR-PM1 species at the SGP site were determined from back trajectory analyses. NR-PM1 mass concentration was dominated by organics for the majority of the study with the exception of winter, when NH4N33 increased due to transport of precursor species from surrounding urban and agricultural regions and also due to cooler temperatures. Chapter 5 is a continuation of chapter 4, where we will explore the use of the multilinear engine (ME-2) as a factor analysis technique, which is an algorithm used for solving the bilinear model called positive matrix factorization (PMF). The importance of ME-2 and its potential application on the long-term aerosol chemical speciation monitor (ACSM) data collected from the Department of Energy (DOE) Southern Great Plains (SPG) site will be discussed. ME-2 was performed on 19 months of OA mass spectral data obtained from the ACSM at the SGP site. Evaluation of ME-2 results are presented, followed by comparison of ME-2 factor results with corresponding OACOMP factor results reported in chapter 4. We show that ME-2 can determine a biomass burning organic aerosol (BBOA) factor during periods when OACOMP cannot. (Abstract shortened by ProQuest.)
Book Synopsis Organic Aerosol Sources and Chemistry by : Yunliang Zhao
Download or read book Organic Aerosol Sources and Chemistry written by Yunliang Zhao and published by . This book was released on 2012 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding organic aerosol (OA) sources and secondary OA (SOA) formation is crucial to elucidate their human health and climate change effects, but has been limited by lack of instrumentation capable of in-situ measurements of organic speciation in the atmosphere across the vapor pressure range of semi-volatile organic compounds (SVOCs) and OA. This dissertation describes 1) the development of a novel instrument based on a thermal desorption aerosol gas chromatograph (TAG), called semi-volatile TAG (SV-TAG) which enables quantitative measurements of specific chemical tracers in SVOCs and OA and 2) application of this new instrument to investigate the various source contributions to OA and SOA formation. The development of the SV-TAG was initiated by employing a denuder difference method to improve the capability of the TAG for quantitative gas/particle separation. Using this technique, hourly time resolution in-situ measurements of organic species were made and then used to investigate the pathways of gas-to-particle partitioning for oxygenated compounds and particle-phase organics were used for source apportionment calculations. The measurements of gas/particle partitioning of phthalic acid, pinonaldehyde and 6, 10, 14-trimethyl-2-pentadecanone were explored to elucidate the pathways of gas-to-particle partitioning whereby SOA was formed. The observations show that multiple pathways of gas-to-particle partitioning contribute to formation of SOA in the atmosphere and the dominance of different pathways are compound-dependent. Absorption into particles is shown to be the dominant pathway for 6, 10, 14-trimethyl-2-pentadecanone to contribute to SOA in Bakersfield, CA. The major pathway to form particle-phase phthalic acid is likely attributed to formation of condensable salts through reactions between phthalic acid and gas-phase ammonia. The observations of pinonaldehyde in particles while inorganic acids in particles were fully neutralized suggest that the occurrence of reactive uptake of pinonaldehyde onto particles does not require the presence of inorganic acids. The relationship between particle-phase pinonaldehyde and RH suggests that aerosol water content plays a significant role in the formation of particle-phase pinonaldehyde. To investigate the contributions of various sources to OA in Bakersfield, CA, positive matrix factorization (PMF) analysis was performed on a subset of the measured particle-phase organic compounds. Six OA source factors were identified, including one representing primary organic aerosol (POA), four different types of secondary organic aerosol (SOA) representing local, regional, and nighttime production, and one representing a complex mixture of additional OA sources that were not further resolvable. POA accounted for 15% of OA on average with a significant contribution from local vehicles. SOA was the dominant contributor to OA, accounting for on average 72% of OA. The rest of OA was unresolved as a mixture of OA sources. Both local and regional SOA had a significant contribution to OA during the day but regional SOA was the largest contributor to OA during the afternoon. SOA formed from the oxidation of biogenic SOA precursors substantially contributed to OA at night. The absorption of organic compounds into particles is suggested to be the major pathway to form SOA, although other pathways also played significant roles. To achieve quantitative collection of SVOCs following improved gas/particle separation, a new collection and thermal desorption system was developed with the key component being a passivated metal fiber filter collector. This final configuration of the SV-TAG enabled in-situ quantitative measurements of speciated SVOCs with vapor pressures lower than n-tetradecane (C14). The capability for measurements of gas/particle partitioning was demonstrated by measurements of n-alkanes in both gas and particle phases. Organic tracers in both gas and particle phases can be quantified. Percentages of speciated organic compounds in total measured organics can be estimated. For example, ~7% and less than 1% of total measured organics in the same retention range of n-alkanes (C14-C20) in the atmosphere in Berkeley, CA were accounted for by the sum of measured n-alkanes (C14-C20) and the sum of n alkylcyclohexanes (C14-C20). The SV-TAG has been demonstrated to enable investigation of the pathways of gas-to-particle partitioning and source apportionment of OA with hourly time resolution. The SV-TAG is also capable of quantitative measurements of speciated SVOCs, defining their gas/particle partitioning in-situ for the first time, and providing observational constraints on the abundance of SVOCs with which to investigate their primary emissions, chemical transformation, and fate.
Book Synopsis Measuring and Modeling the Composition of Secondary Organic Aerosol by : Michael James Apsokardu
Download or read book Measuring and Modeling the Composition of Secondary Organic Aerosol written by Michael James Apsokardu and published by . This book was released on 2021 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: The modeling and measurement approaches discussed in this dissertation are tools that future members of our research group will be able to utilize for studies of measuring and modeling the composition of secondary organic aerosol. Both current and future projects using measurement and modeling approaches are discussed at the conclusion of this dissertation.
Book Synopsis Thermally Evolved & Separated Composition of Atmospheric Aerosols by : Yaping Zhang
Download or read book Thermally Evolved & Separated Composition of Atmospheric Aerosols written by Yaping Zhang and published by . This book was released on 2015 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric organic aerosols are composed of thousands of individual compounds, interacting with climate through changes in aerosol optical properties and cloud interactions, and can be detrimental to human health. Aerosol mass spectrometry (MS) and gas chromatography (GC)-separated MS measurements have been utilized to better characterize the chemical composition of this material that comes from a variety of sources and experiences continuous oxidation while in the atmosphere. This dissertation describes the development of a novel rapid data analysis method for grouping of major components within chromatography-separated measurements and first application using thermal desorption aerosol gas chromatograph (TAG) -- MS data. Chromatograms are binned and inserted directly into a positive matrix factorization (PMF) analysis to determine major contributing components, eliminating the need for manual compound integrations of hundreds of resolved molecules, and incorporating the entirety of the eluting MS signal, including Unresolved Complex Mixtures (UCM) and decomposition products that are often ignored in traditional GC-MS analysis. Binned GC-MS data has three dimensions: (1) mass spectra index m/z, (2) bin number, and (3) sample number. PMF output is composed of two dimensions; factor profiles and factor time series. The specific arrangement of the input data (three dimensions of variation structured as a two dimensional matrix) in a two dimensional PMF analysis affects the structure of the PMF profiles and time series output. If mass spectra index is in the profile dimension, and bin number and sample number are in the time series dimension, PMF groups components into factors with similar mass spectra, such as major contributing individual compounds, UCM with similar functional composition, and homologous compound series. This type of PMF analysis is described as the binning method for chromatogram deconvolution, and is presented in Chapter 2. If the sample number is in the time series dimension, and the bin number and mass spectra index, arranged as mass spectra resolved retention time/chromatogram (bin number), are in the profile dimension, PMF groups components with similar time series trends. This type of PMF analysis is described as binning method for source apportionment, and is described in Chapter 3. The binning methods are compared to traditional compound integration methods using previously-collected hourly ambient samples from Riverside, CA during the 2005 Study of Organic Aerosols at Riverside (SOAR) field campaign, as discussed in Chapters 2-3. Further application of the binning method for source apportionment is performed on newly acquired hourly TAG data from East St. Louis, IL, operated as part of the 2013 St. Louis Air Quality Regional Study (SLAQRS). Major sources of biogenic secondary organic aerosol (SOA), anthropogenic primary organic aerosol (POA) were identified, as described in detail in Chapter 4. Finally, our PMF separation method was tested for reliability using primary and secondary sources in a controlled laboratory system. As shown in Chapter 5, we find that for application of PMF on receptor measurements, high signal intensity and unique measurement profiles, like those found in TAG chromatograms, are keys to successful source apportionment. The binning method with component separation by PMF may be a valuable analysis technique for other complex data sets that incorporate measurements (e.g., mass spectrometry, spectroscopy, etc.) with additional separations (e.g., volatility, hygroscopicity, electrical mobility, etc.).
Book Synopsis Analytical Chemistry of Aerosols by : Kvetoslav R. Spurny
Download or read book Analytical Chemistry of Aerosols written by Kvetoslav R. Spurny and published by CRC Press. This book was released on 1999-04-23 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt: Until the 1980s, researchers studied and measured only the physical properties of aerosols. Since the 80s, however, interest in the physicochemcal properties of aerosols has grown tremendously. Scientists in environmental hygiene, medicine, and toxicology have recognized the importance held by the chemical composition and properties of aerosols and the interactions of inhaled, "bad" aerosols. This book offers the first comprehensive treatment of modern aerosol analytical methods, sampling and separation procedures, and environmental applications, and offers critical reviews of the latest literature. This important field has developed rapidly in the last 15 years, but until now, no book effectively summarized or analyzed the existing research. Analytical Chemistry of Aerosols reviews procedures, techniques, and trends in the measurement and analysis of atmospheric aerosols. With contributions from acknowledged, international experts, the book discusses various methods of bulk analysis, single particle analysis, and the analysis of special aerosol systems, including fibrous and bacterial aerosols.
Book Synopsis Characterization of Secondary Organic Aerosol Precursors Using Two-Dimensional Gas Chromatography with Time of Flight Mass Spectrometry (GC×GC/TOFMS) by :
Download or read book Characterization of Secondary Organic Aerosol Precursors Using Two-Dimensional Gas Chromatography with Time of Flight Mass Spectrometry (GC×GC/TOFMS) written by and published by . This book was released on 2013 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: The oxidation of volatile organic compounds (VOCs) plays a role in both regional and global air quality through the formation of secondary organic aerosols (SOA). More than 1000TgC/yr of non-methane VOCs are emitted from biogenic sources (significantly greater than from anthropogenic sources). Despite this magnitude and potential importance for air quality, the body of knowledge around the identities, quantities and oxidation processes of these compounds is still incomplete (e.g., Goldstein & Galbally, 2007; Robinson et al., 2009). Two-dimensional gas chromatography paired with time-of-flight mass spectrometry (GC×GC/TOFMS) is a powerful analytical technique which is explored here for its role in better characterizing biogenic VOCs (BVOCs) and thus SOA precursors.
Book Synopsis Properties of Secondary Organic Aerosol in the Ambient Atmosphere by : Christopher James Hennigan
Download or read book Properties of Secondary Organic Aerosol in the Ambient Atmosphere written by Christopher James Hennigan and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis characterizes properties of ambient secondary organic aerosol (SOA), an important and abundant component of particulate matter. The findings presented in this thesis are significant because they represent the results from ambient measurements, which are relatively scarce, and because they report on properties of SOA that, until now, were highly uncertain. The analyses utilized the fraction of particulate organic carbon that was soluble in water (WSOCp) to approximate SOA concentrations in two largely different urban environments, Mexico City and Atlanta. In Mexico City, measurements of atmospheric gases and fine particle chemistry were made at a site ~ 30 km down wind of the city center. Using box model analyses and a comparison to ammonium nitrate aerosol, a species whose thermodynamic properties are generally understood, the morning formation and mid-day evaporation of SOA are investigated. In Atlanta, simultaneous measurements of WSOCp and water-soluble organic carbon in the gas phase (WSOCg) were carried out for an entire summer to investigate the sources and partitioning of WSOC. The results suggest that both WSOCp and WSOCg were secondary and biogenic, except possibly in several strong biomass burning events. The gas/particle partitioning of WSOC in Atlanta was investigated through the parameter, Fp, which represented the fraction of WSOC in the particle phase. Factors that appear to influence WSOC partitioning in Atlanta include ambient relative humidity and the WSOCp mass concentration. There was also a relationship between the NOx concentration and Fp, though this was not likely related to the partitioning process. Temperature did not appear to impact Fp, though this may have been due to positive relationships WSOCp and WSOCg each exhibited with temperature. Neither the total Organic Carbon aerosol mass concentration nor the ozone concentration impacted WSOC partitioning.
Book Synopsis Molecular Composition and Chemical Transformation of Secondary Organic Aerosols from Biogenic Precursors by : Tran Bao Nguyen
Download or read book Molecular Composition and Chemical Transformation of Secondary Organic Aerosols from Biogenic Precursors written by Tran Bao Nguyen and published by . This book was released on 2012 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: There are large gaps surrounding our understanding of secondary organic aerosols (SOA), which represent a significant fraction of fine particulate matter globally. One of the most difficult aspects of SOA to characterize is the molecular composition, because it is both complex and dynamic. However, the composition of SOA determines to a large extent the impact SOA has on climate, atmospheric chemistry, and human health. The main focus of this dissertation is the detailed composition analysis of SOA generated from important biogenic precursors and the characterization of chemistry induced by their simulated interaction with clouds, anthropogenic pollutants, and solar radiation. In particular, the gas- and aerosol-phase compounds associated with SOA from isoprene, the most abundant volatile organic compound emitted from the biosphere, are studied with the advanced technique of high-resolution mass spectrometry (HR MS). Many SOA compounds, particularly nitrogen-containing organics, are reported for the first time. Spectroscopy tools like UV-Vis, FT-IR and NMR are also used to characterize optical properties and molecular structures of SOA compounds. A secondary focus of this dissertation is to describe brown carbon formation from the ammonium- and amino acid-mediated aging of limonene SOA. Brown carbon changes the optical properties of SOA, but the sources are poorly understood. The experiments presented in this dissertation aim to elucidate the previously unknown precursors, kinetics and products of the reaction. The molecular detail gained from the HR-MS and spectroscopic analyses provides tremendous insight into the formation mechanism and further atmospheric reactions of SOA.
Book Synopsis Understanding Organic Aerosol Formation Processes in Atmosphere Using Molecular Markers by : Grazia Maria Lanzafame
Download or read book Understanding Organic Aerosol Formation Processes in Atmosphere Using Molecular Markers written by Grazia Maria Lanzafame and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic aerosols (OA) account for a large fraction of ambient air particulate matter and have strong impacts on air quality and climate. As their sources and atmospheric formation processes, notably for secondary OA (SOA), are still not fully understood, their concentrations are often underestimated by air quality models. This work aimed at improving OA modelling by implementing specific organic molecular marker emissions and formation processes into the chemistry-transport model CHIMERE. It was based on the comparison of model outputs with measurements from field studies performed in the Paris region (suburban site of SIRTA, 25 km SW of Paris) over 2015 and 10 French urban locations in winter 2014-2015. 25 biogenic and anthropogenic SOA markers have been quantified in both, particulate and gas phases and the formation pathways of 10 have been developed and simulated using CHIMERE. The evolution of levoglucosan concentrations (biomass burning marker) has been also modeled. The results obtained showed that sources and precursor emissions (missing or underestimated), radical concentrations (NO, HO2 and RO2) and the lack of formation pathways, are key parameters for the simulation of SOA markers. Gas/particle partitioning seemed poorly linked to the T°C while the inclusion of hydrophilic non-ideal partitioning, usually neglected, seemed essential. Levoglucosan was well simulated, even if some underestimations existed in some regions. A significant theoretical gaseous fraction was also highlighted. The model/measurements comparison of molecular markers is a powerful tool to evaluate precursor emissions, physicochemical processes and in the end, to estimate OA sources.
Book Synopsis Characterizing the Origins of Atmospheric Aerosol Through Receptor Modeling of Multiple Time-scale Chemical Speciation Measurements by : Maygan L. McGuire
Download or read book Characterizing the Origins of Atmospheric Aerosol Through Receptor Modeling of Multiple Time-scale Chemical Speciation Measurements written by Maygan L. McGuire and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric aerosol is known to have adverse effects on visibility, population health, and climate. The sources and processes that contribute to atmospheric aerosol can be studied through a variety of aerosol chemical speciation techniques, and results from these analyses can be analyzed through factor analytic receptor modeling to identify origins and ultimately design effective mitigation strategies. While receptor modeling has been applied to nearly every type of aerosol speciation measurement, there has been little discussion in regards to how inputs, in terms of different aspects of measurement, relate to the answers that receptor modeling can provide in terms of air quality management and atmospheric processes. In this thesis, the factor analytic technique Positive Matrix Factorization (PMF) was applied to four sets of aerosol chemical speciation measurements of varied time resolution and chemical breadth, from the receptor region of greater Windsor, Ontario. At the outset of this research, receptor modeling was dominated by the use of long-term, low time-resolution integrated filter measurements. This research involved the extension of receptor modeling towards more advanced, state-of-the-art sub-hourly time-resolution aerosol measurements, including trace element measurements from a semi-continuous elements in aerosol sampler (SEAS), bulk aerosol mass spectra from an Aerodyne Aerosol Mass Spectrometer (AMS), and single particle mass spectra from a TSI Aerosol Time-of-Flight Mass Spectrometer (ATOFMS). Receptor modeling of measurements from these techniques each yielded insights specific to the method, time of year and duration of sampling. Taken together, receptor modeling results from the high time-resolution measurement methods provided a far more detailed understanding of the variety of the sources and processes that contribute to aerosol composition and concentration in greater Windsor, as compared to long-term, low time-resolution integrated filter measurements alone. In total, 14 different factors were identified. Receptor modeling of integrated filter measurements established that secondary aerosol dominated greater Windsor's PM2.5 mass (e.g., Secondary Sulphate and Nitrate contributed 37 and 24% respectively to Windsor's average PM2.5 of 12ug m-3); other local, and local-to-regional anthropogenic factors, such as Traffic, Steel Mills, and Oil Combustion emissions, also contributed (18%, 4%, and 2% by mass respectively). However, receptor modeling using high time-resolution measurements provided more detailed perspectives into aerosol origins. For instance, receptor modeling of AMS and ATOFMS measurements highlighted that secondary nitrate, identified in past studies in the region as mostly regional, is actually a superposition of regional and local nitrate, with local nitrate forming overnight in both winter and summer. Single particle mass spectral measurements confirmed as hypothesized, that regional summertime secondary sulphate and nitrate aerosol consists of a homogeneous external mixture of particles that are internally mixed with sulphate, nitrate, organic and elemental carbon. Traffic aerosol was shown to contain fresh, hydrocarbon-like organic aerosol, as well as black carbon and trace elements such as Ba and Fe, but showed a wide range of average concentrations (0.94 - 2.18ug m-3), specific to the circumstances of measurement. An integrated analysis across all four studies highlighted the strengths and limitations of the various chemical speciation techniques and receptor modeling approaches used in each study. For instance, receptor modeling of SEAS measurements that included refractory elements provided a source-based perspective useful for primary source identification, while receptor modeling of non-refractory combined organic and inorganic mass spectra from the AMS provided a more process-based perspective useful for characterizing the degree of aerosol chemical processing. Receptor modeling results of ATOFMS single particle measurements provided the most detailed representation of factors, highlighting both the internal and external mixing states of particle-types. An overarching conclusion emerged from this work, in that the degree of factor deconvolution in factor analytic receptor modeling is inter-related with the variability in chemical composition of the aerosol being measured, the properties of measurement, and modeling parameters. With a priori consideration given to this conclusion and more intentional study design, receptor modeling studies can lead to improved factor resolution, and ultimately more reliable and useful results.
Book Synopsis Sensitivity of Emission Precursors and Thermodynamic Parameters to Secondary Organic Aerosol Formation in Southeast Texas Using CMAQ Modeling System by : Dhruvi Vora
Download or read book Sensitivity of Emission Precursors and Thermodynamic Parameters to Secondary Organic Aerosol Formation in Southeast Texas Using CMAQ Modeling System written by Dhruvi Vora and published by . This book was released on 2006 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Modeling Secondary Organic Aerosol Formation from Emissions of Combustion Sources by : Shantanu Hemant Jathar
Download or read book Modeling Secondary Organic Aerosol Formation from Emissions of Combustion Sources written by Shantanu Hemant Jathar and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
