Chemistry of Secondary Organic Aerosol Formation from the Reaction of Hydroxyl Radicals with Aromatic Compounds

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ISBN 13 : 9781303507403
Total Pages : 185 pages
Book Rating : 4.5/5 (74 download)

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Book Synopsis Chemistry of Secondary Organic Aerosol Formation from the Reaction of Hydroxyl Radicals with Aromatic Compounds by : Christen Michelle Strollo Gordon

Download or read book Chemistry of Secondary Organic Aerosol Formation from the Reaction of Hydroxyl Radicals with Aromatic Compounds written by Christen Michelle Strollo Gordon and published by . This book was released on 2013 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: Secondary Organic Aerosol (SOA) can have significant impacts on visibility, human health, and global climate, and a more detailed understanding of the roles of both gas-phase and heterogeneous/multiphase chemistry is needed to develop air quality models that accurately represent the formation of SOA from the oxidation of aromatic hydrocarbons. The objective of this dissertation is to investigate the mechanisms and products of SOA formation from the OH radical-initiated reaction of aromatics in an environmental chamber. This is done using a combination of thermal desorption particle beam mass spectrometry, functional group and CHON elemental analysis, and UV spectroscopy. Chapter 2 investigates the variability of SOA yields measured for reactions of m-xylene and other methylbenzenes as a function of humidity, seed particle, OH source, NO x concentration, light intensity, and mass loading. The most significant factor that determined SOA yields was the amount of m -xylene reacted. The chapter concludes with a discussion of a series of experiments conducted to isolate the contribution to SOA formation of specific primary gas-phase products of the m -xylene reaction. Chapter 3 examines the formation of SOA from the oxidation of 3-methylfuran, which produces among other compounds an [Alpha, Beta]-unsaturated dicarbonyl that is also a major product of the oxidation of m -xylene. We have determined that SOA forms from the heterogeneous/multiphase oligomerization of primary reaction products to form esters, hemiacetals, and acetals, and not through second-generation reactions. Chapter 4 discusses the chemical composition of SOA formed from the reaction of m -xylene and how the variables detailed in Chapter 2 affect the composition. Experiments were carried out with deuterated m-xylene to confirm that SOA is dominated by hemiacetals formed from C8 ring-opened primary products and their second-generation products. Finally, Chapter 5 shows that SOA formed from the oxidation of benzaldehyde in the absence of NOx is largely composed of oligomeric products formed through heterogeneous/multiphase reactions involving benzoic acid, peroxybenzoic acid, phenol, and benzaldehyde.

Secondary Organic Aerosol Formation from Aromatic Hydrocarbons

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ISBN 13 :
Total Pages : 532 pages
Book Rating : 4.3/5 (121 download)

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Book Synopsis Secondary Organic Aerosol Formation from Aromatic Hydrocarbons by : Chen Song

Download or read book Secondary Organic Aerosol Formation from Aromatic Hydrocarbons written by Chen Song and published by . This book was released on 2006 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Atmospheric Multiphase Chemistry

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Publisher : John Wiley & Sons
ISBN 13 : 1119422426
Total Pages : 539 pages
Book Rating : 4.1/5 (194 download)

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Book Synopsis Atmospheric Multiphase Chemistry by : Hajime Akimoto

Download or read book Atmospheric Multiphase Chemistry written by Hajime Akimoto and published by John Wiley & Sons. This book was released on 2020-06-02 with total page 539 pages. Available in PDF, EPUB and Kindle. Book excerpt: An important guide that highlights the multiphase chemical processes for students and professionals who want to learn more about aerosol chemistry Atmospheric Multiphase Reaction Chemistry provides the information and knowledge of multiphase chemical processes and offers a review of the fundamentals on gas-liquid equilibrium, gas phase reactions, bulk aqueous phase reactions, and gas-particle interface reactions related to formation of secondary aerosols. The authors—noted experts on the topic—also describe new particle formation, and cloud condensation nuclei activity. In addition, the text includes descriptions of field observations on secondary aerosols and PM2.5. Atmospheric aerosols play a critical role in air quality and climate change. There is growing evidence that the multiphase reactions involving heterogeneous reactions on the air-particle interface and the reactions in the bulk liquid phase of wet aerosol and cloud/fog droplets are important processes forming secondary aerosols in addition to gas-phase oxidation reactions to form low-volatile compounds. Comprehensive in scope, the book offers an understanding of the topic by providing a historical overview of secondary aerosols, the fundamentals of multiphase reactions, gas-phase reactions of volatile organic compounds, aqueous phase and air-particle interface reactions of organic compound. This important text: Provides knowledge on multiphase chemical processes for graduate students and research scientists Includes fundamentals on gas-liquid equilibrium, gas phase reactions, bulk aqueous phase reactions, and gas-particle interface reactions related to formation of secondary aerosols Covers in detail reaction chemistry of secondary organic aerosols Written for students and research scientists in atmospheric chemistry and aerosol science of environmental engineering, Atmospheric Multiphase Reaction Chemistry offers an essential guide to the fundamentals of multiphase chemical processes.

Photochemistry of Aromatic Hydrocarbons

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ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (819 download)

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Book Synopsis Photochemistry of Aromatic Hydrocarbons by : Inseon Suh

Download or read book Photochemistry of Aromatic Hydrocarbons written by Inseon Suh and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Aromatic hydrocarbons constitute an important fraction (~20%) of total volatile organic compounds (VOCs) in the urban atmosphere. A better understanding of the aromatic oxidation and its association in urban and regional ozone and organic aerosol formation is essential to assess the urban air pollution. This dissertation consists of two parts: (1) theoretical investigation of the toluene oxidation initiated by OH radical using quantum chemical and kinetic calculations to understand the mechanism of O3 and SOA precursors and (2) experimental investigation of atmospheric new particle formation from aromatic acids. Density functional theory (DFT) and ab initio multiconfigurational calculations have been performed to investigate the OH-toluene reaction. The branching ratios of OH addition to ortho, para, meta, and ipso positions are predicted to be 0.52, 0.34, 0.11, and 0.03, respectively, significantly different from a recent theoretical study of the same reaction system. Aromatic peroxy radicals arising from initial OH and subsequent O2 additions to the toluene ring are shown to cyclize to form bicyclic radicals rather than undergoing reaction with NO under atmospheric conditions. Isomerization of bicyclic radicals to more stable epoxide radicals possesses significantly higher barriers and hence has slower rates than O2 addition to form bicyclic peroxy radicals. At each OH attachment site, only one isomeric pathway via the bicyclic peroxy radical is accessible to lead to ring cleavage. Decomposition of the bicyclic alkoxy radicals leads primarily to formation of glyoxal and methyl glyoxal along with other dicarbonyl compounds. Atmospheric aerosols often contain a considerable fraction of organic matter, but the role of organic compounds in new nanometer-sized particle formation is highly uncertain. Laboratory experiments show that nucleation of sulfuric acid is considerably enhanced in the presence of aromatic acids. Theoretical calculations identify the formation of an unusually stable aromatic acid-sulfuric acid complex, which likely leads to a reduced nucleation barrier. The results imply that the interaction between organic and sulfuric acids promotes efficient formation of organic and sulfate aerosols in the polluted atmosphere because of emissions from burning of fossil fuels, which strongly impact human health and global climate.

Chemistry of Secondary Organic Aerosol Formation from Reactions of Alkenes with Ozone and Nitrate Radicals

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ISBN 13 :
Total Pages : 162 pages
Book Rating : 4.3/5 (121 download)

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Book Synopsis Chemistry of Secondary Organic Aerosol Formation from Reactions of Alkenes with Ozone and Nitrate Radicals by : Huiming Gong

Download or read book Chemistry of Secondary Organic Aerosol Formation from Reactions of Alkenes with Ozone and Nitrate Radicals written by Huiming Gong and published by . This book was released on 2003 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt:

The Mechanisms of Atmospheric Oxidation of the Aromatic Hydrocarbons

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Publisher : Oxford University Press
ISBN 13 : 9780199771547
Total Pages : 570 pages
Book Rating : 4.7/5 (715 download)

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Book Synopsis The Mechanisms of Atmospheric Oxidation of the Aromatic Hydrocarbons by : Jack G. Calvert

Download or read book The Mechanisms of Atmospheric Oxidation of the Aromatic Hydrocarbons written by Jack G. Calvert and published by Oxford University Press. This book was released on 2002-02-14 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text reviews many of the aspects of the chemistry of the aromatic hydrocarbons and a consensus evaluation of the data by seven of the leading atmospheric scientists. The book covers topics ranging from the relative importance of the compounds in ozone and haze development to methods of estimating elemantary rate coefficients based on structural features of the compounds to mechanisms of aerosol generation and atmostpheric reaction of the polycyclic compounds to photochemical processes. It identifies features of the aromatic hydrocarbons requiring further study and appendicies give the structural formulas and nomenclature of the compounds reviewed in the book.

Advances In Atmospheric Chemistry - Volume 2: Organic Oxidation And Multiphase Chemistry

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Publisher : World Scientific
ISBN 13 : 9813271841
Total Pages : 616 pages
Book Rating : 4.8/5 (132 download)

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Book Synopsis Advances In Atmospheric Chemistry - Volume 2: Organic Oxidation And Multiphase Chemistry by : John R Barker

Download or read book Advances In Atmospheric Chemistry - Volume 2: Organic Oxidation And Multiphase Chemistry written by John R Barker and published by World Scientific. This book was released on 2019-01-07 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt: This series presents authoritative invited summaries of research on atmospheric chemistry in a changing world. These range from comprehensive reviews of major subject areas to focused accounts by individual research groups. The topics may include laboratory studies, field measurements, in situ monitoring and remote sensing, studies of composition, chemical modeling, theories of atmospheric chemistry and climate, feedback mechanisms, emissions and deposition, biogeochemical cycles, and the links between atmospheric chemistry and the climate system at large.Volume 2 comprises chapters describing research on multiphase chemistry affecting air quality in China, on multiphase chemistry of organic compounds leading to secondary organic aerosol formation, on biogeochemical cycles involving ammonia, on oxidation of aromatic compounds, on reactions of Criegee intermediates (important in oxidation of alkenes), and on laboratory and field measurements of isotopic fractionation in the atmosphere.

Secondary Organic Aerosol (SOA) Formation from Aqueous OH Radical Oxidation of Dicarbonyl Compounds in the Atmosphere

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ISBN 13 :
Total Pages : 219 pages
Book Rating : 4.:/5 (697 download)

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Book Synopsis Secondary Organic Aerosol (SOA) Formation from Aqueous OH Radical Oxidation of Dicarbonyl Compounds in the Atmosphere by : Yi Tan

Download or read book Secondary Organic Aerosol (SOA) Formation from Aqueous OH Radical Oxidation of Dicarbonyl Compounds in the Atmosphere written by Yi Tan and published by . This book was released on 2010 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: Secondary organic aerosols (SOA) affect visibility, health and global climate. Current chemical transport models cannot represent SOA in the free troposphere. Fog/cloud processing, which is the dominant source of atmospheric sulfate, has been recognized as a missing source of SOA globally. Aqueous photooxidation of water-soluble products (e.g., glyoxal and methylglyoxal) of gas-phase photochemistry yields low-volatility compounds including oxalic acid. When this chemistry takes place in clouds and fogs followed by droplet evaporation (or if this chemistry occurs in aerosol water) then products remain in part in the particle phase, forming SOA. However, current aqueous SOA formation mechanism has not shown how the starting concentrations of precursors and presence of acidic sulfate affect product formation. Aqueous phase photochemical batch reactions were conducted with glyoxal and methylglyoxal at cloud relevant concentrations, using hydrogen peroxide photolysis as the hydroxyl radical (OH) source. Experiments were repeated at higher concentrations and with/without sulfuric acid. Precursors and products were investigated using ion chromatography (IC), electrospray ionization mass spectrometry (ESI-MS), and IC-ESI-MS. Products included carboxylic acids and higher molecular weight compounds, which are major constituents of aerosols. Sulfuric acid shows little effect on product formation. Dilute aqueous chemistry models successfully reproduced product formation for glyoxal and methylglyoxal at cloud relevant conditions, but measurements deviated from predictions from predictions at elevated concentrations. Higher molecular weight products become increasingly important as precursor concentration increases. Aqueous radical-radical reactions provide explanations for observed higher molecular weight products. Additionally, acetic acid is identified as an SOA precursor for the first time. This work provides an improved understanding of aqueous phase dicarbonyl oxidation mechanism and the overall significance of aqueous SOA formation. Kinetic data are made available to regional and global atmospheric models, and the mechanism described in this work will help people to mitigate adverse aerosol effects.

Secondary Organic Aerosol Formation from Reactions of Linear, Branched and Cyclic Alkanes with OH Radicals in the Presence of NO[subscript X]

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ISBN 13 :
Total Pages : 396 pages
Book Rating : 4.3/5 (121 download)

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Book Synopsis Secondary Organic Aerosol Formation from Reactions of Linear, Branched and Cyclic Alkanes with OH Radicals in the Presence of NO[subscript X] by : Yong Bin Lim

Download or read book Secondary Organic Aerosol Formation from Reactions of Linear, Branched and Cyclic Alkanes with OH Radicals in the Presence of NO[subscript X] written by Yong Bin Lim and published by . This book was released on 2008 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Mechanistic Studies of Atmospheric Chemical Reactions of Hydroxyl Radicals with Aromatic Hydrocarbons, Including 2-ring Polycyclic Aromatic Hydrocarbons, and Terminal Alkenes

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ISBN 13 :
Total Pages : 416 pages
Book Rating : 4.3/5 (121 download)

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Book Synopsis Mechanistic Studies of Atmospheric Chemical Reactions of Hydroxyl Radicals with Aromatic Hydrocarbons, Including 2-ring Polycyclic Aromatic Hydrocarbons, and Terminal Alkenes by : Noriko Nishino

Download or read book Mechanistic Studies of Atmospheric Chemical Reactions of Hydroxyl Radicals with Aromatic Hydrocarbons, Including 2-ring Polycyclic Aromatic Hydrocarbons, and Terminal Alkenes written by Noriko Nishino and published by . This book was released on 2009 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Formation and Chemical Evolution of Secondary Organic Aerosol from Aqueous-phase Reactions of Atmospheric Phenols

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ISBN 13 : 9781339824093
Total Pages : pages
Book Rating : 4.8/5 (24 download)

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Book Synopsis Formation and Chemical Evolution of Secondary Organic Aerosol from Aqueous-phase Reactions of Atmospheric Phenols by : Lu Yu

Download or read book Formation and Chemical Evolution of Secondary Organic Aerosol from Aqueous-phase Reactions of Atmospheric Phenols written by Lu Yu and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Secondary organic aerosol (SOA) is formed and transformed in atmospheric aqueous phases (e.g., cloud and fog droplets and deliquesced airborne particles containing small amounts of water) through a multitude of chemical and physical processes. Understanding the formation and transformation processes of SOA via aqueous-phase reactions is important for properly presenting its atmospheric evolution pathways in models and for elucidating its climate and health effects. Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the formation and evolution of phenol (C6H6O), guaiacol (C7H8O2; 2-methoxyphenol) and syringol (C8H10O3; 2,6-dimethoxyphenol) and with two major aqueous phase oxidants -- the triplet excited state of an aromatic carbonyl (3C*) and hydroxyl radical (·OH) - and interpret the reaction mechanisms. In addition, given that dissolved organic matter (DOM) is an important component of fog and cloud water and that it can undergo aqueous reactions to form more oxidized, less volatile species, we further investigate the photochemical processing of DOM in fog water to gain insights into the aqueous-phase processing of organic aerosol (OA) in the atmosphere. In Chapter 2, we thoroughly characterize the bulk chemical and molecular compositions of phenolic aqSOA formed at half-life (t[subscript 1/2]), and interpret the formation mechanisms. We find that phenolic aqSOA formed at t[subscript 1/2] is highly oxygenated with atomic oxygen-to-carbon ratio (O/C) in the range of 0.85-1.23. Dimers, higher oligomers (up to hexamers), functionalized monomers and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acids are detected. Compared with ·OH-mediated reactions, reactions mediated by 3C* are faster and produce more oligomers and hydroxylated species at t[subscript1/2]. We also find that aqSOA shows enhanced light absorption in the UV-vis region, suggesting that aqueous-phase reactions of phenols are an important source of secondary brown carbon in the atmosphere, especially in regions impacted by biomass burning. In Chapter 3, we investigate the chemical evolution of phenolic aqSOA via aqueous-phase reactions on the molecular level and interpret the aging mechanisms. Our results indicate that oligomerization is an important aqueous reaction pathway for phenols, especially during the initial stage of photooxidation. Functionalization and fragmentation become dominant at later stages, forming a variety of functionalized aromatic and ring-opening products with higher carbon oxidation states. Fragmentation reactions eventually dominate the photochemical evolution of phenolic aqSOA, forming a large number of highly oxygenated ring-opening molecules. In addition, phenolic aqSOA has a wide range of saturation vapor pressures (C*), varying from 10−20 [mu]g m−3 for functionalized phenolic oligomers to 10 [mu]g m−3 for ring-opening species with number of carbon less than 6. The detection of abundant extremely low volatile organic compounds (ELVOC) indicates that aqueous reactions of phenolic compounds are likely an important source of ELVOC in the atmosphere. Chapter 3 investigates the molecular transformation with aging based on the characterization of three aqSOA filter samples collected at the defined time intervals of the photoreaction. However, the chemical evolution of aqSOA products with hours of illumination at a higher time resolution is largely unknown. In Chapter 4, we investigate the chemical evolution of aqSOA at a 1-min time resolution based on high-resolution aerosol mass spectrometer (AMS) analysis. This is important for understanding the continuous evolution of phenolic aqSOA with aging as well as for elucidating the formation and transformation of different generations of products. Our results suggest that dimer and higher-order oligomers (trimers, tetramers, etc.) are formed continuously during the first 1-2 hours of photoreaction but show a gradual decrease afterwards. Functionalized derivatives grow at a later time and then gradually decrease. Highly oxidized ring-opening species continuously increase over the course of reactions. Positive matrix factorization (PMF) analysis of the AMS spectra of phenolic aqSOA identifies multiple factors, representing different generations of products. The 1st-generation products include dimers, higher-order oligomers and their oxygenated derivatives. The 2nd-generation products include oxygenated monomeric derivatives. The 3rd-generation products include highly oxidized ring-opening species. In Chapter 5, we investigate the evolution of dissolved organic matter (DOM) in fog water. Our results show that the mass concentration of DOM[subscript OA] (i.e., low-volatility DOM in fog water) is enhanced over the course of illumination, with continuous increase of O/C and atomic nitrogen-to-carbon ratio (N/C). The increase of DOM[subscript OA] is due to the incorporation of oxygen- and nitrogen-containing functional groups into the molecules. The aqueous aging of DOM[subscript OA] can be modeled as a linear combination of the dynamic variations of 3 factors using PMF analysis. Factor 1 is chemically similar to the DOM[subscript OA] before illumination, which is quickly reacted away. Factor 2 is representative of an intermediate component, which is first formed and then transformed, and O/C of Factor 2 is intermediate between that of Factor 1 and Factor 3. Factor 3 represents highly oxidized final products, which is continuously formed during illumination. Fog DOM absorbs significantly in the tropospheric sunlight wavelengths, but this absorption behavior stays almost constant over the course of illumination, despite the significant change in chemical composition.

Secondary Organic Aerosol Formation from Radical-initiated Reactions of Alkenes

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ISBN 13 :
Total Pages : 289 pages
Book Rating : 4.:/5 (567 download)

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Book Synopsis Secondary Organic Aerosol Formation from Radical-initiated Reactions of Alkenes by : Aiko Matsunaga

Download or read book Secondary Organic Aerosol Formation from Radical-initiated Reactions of Alkenes written by Aiko Matsunaga and published by . This book was released on 2009 with total page 289 pages. Available in PDF, EPUB and Kindle. Book excerpt: The products and mechanisms of secondary organic aerosol (SOA) formation from reactions of 1-alkenes, internal alkenes, and 2-methyl-1-alkenes with OH radicals in the presence of NO[subscript x] were investigated in an environmental chamber and the results used to develop quantitative models for SOA formation. Aerosol chemical composition was analyzed using a thermal desorption particle beam mass spectrometer (TDPBMS), and multifunctional organic nitrate products were quantified using a high-performance liquid chromatograph with UV-vis detector and identified using the TDPBMS and 1H NMR. The major products observed in reactions of linear alkenes were [beta]-hydroxynitrates, dihydroxynitrates, cyclic hemiacetals, dihydrofurans, and dimers formed from dihydroxycarbonyls. Trihydroxynitrates and trihydroxycarbonyls were observed in reactions of 2-methyl-1-alkenes, in addition to the products listed above. Dimers were not observed, apparently because electron donation by the additional methyl group (compared to linear 1-alkenes) reduces the driving force for hemiacetal formation. The measured yields of [beta]-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates were used to calculate relative ratios of 1.0:1.9:4.3 for forming primary, secondary, and tertiary [beta]-hydroxyalkyl radicals by OH radical addition to the C=C double bond, and branching ratios of 0.12, 0.15, and 0.25 for forming [beta]-hydroxynitrates from reactions of primary, secondary, and tertiary â-hydroxyperoxy radicals with NO. The trends are consistent with expected relative stabilities of [beta]-hydroxyalkyl radicals and ß-hydroxyperoxy radical-NO complexes. It should be possible to use these values to estimate product yields from similar reactions of other alkenes. Comparison of measured and model-calculated SOA yields showed that in some cases the models provide accurate predictions of SOA yields, but that uncertainties in gas- and particle-phase chemistry and gas-particle partitioning can lead to significant discrepancies. More limited environmental chamber studies were also carried out on SOA formation from reactions of linear alkenes with NO3 radicals. The major products were [beta]-hydroxynitrates, [beta]-carbonylnitrates, dihydroxynitrates, and hydroxy- and oxo- dinitrooxytetrahydrofurans, which had not been observed previously. It was observed that isomerization of [delta]-hydroxycarbonyls to cyclic hemiacetals, followed by dehydration to highly reactive dihydrofurans that can be further oxidized, can be important sources of SOA from reactions of alkenes with OH and NO3 radicals.

Formation of Organic Aerosol Through Cloud Chemistry

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ISBN 13 :
Total Pages : 120 pages
Book Rating : 4.:/5 (785 download)

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Book Synopsis Formation of Organic Aerosol Through Cloud Chemistry by : Anjuli Ramos-Busot

Download or read book Formation of Organic Aerosol Through Cloud Chemistry written by Anjuli Ramos-Busot and published by . This book was released on 2012 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic particulate matter in the atmosphere plays an important role in climate forcing, visibility, and adverse health effects. Atmospheric organic aerosol is predominantly of secondary origin, formed in the atmosphere. Laboratory photooxidation experiments, atmospheric aerosol measurements below vs. above clouds and at increasing humidity, and modeling studies all suggest that secondary organic aerosol (SOA) forms from water-soluble gases through aqueous chemistry in clouds and wet aerosols (aqSOA). Previous laboratory experiments are simple compared to the atmospheric water media (single compound deionize water solutions), thus a more realistic approach is needed for the understanding of SOA formation through aqueous chemistry. We conducted batch photooxidation experiments with three different rainwater samples from Camden and Pinelands, NJ and hydroxyl radicals (formed from 150 æM H2O2 + UV radiation). We used rainwater (RW) as a surrogate for cloud water in these experiments. SOA precursors and products were identified by real-time Electrospray Ionization -- Mass Spectrometry (ESI-MS, continuous online sampling) and by Ion Chromatography (discrete samples). Precursors were found predominantly in the positive mode, suggesting the presence of aldehydes, alcohols and organic peroxides, and products were found predominantly in the negative mode, suggesting the presence of organic acids. A decrease in the abundance of ions with the same unit mass-to-charge ratio as standards of glyoxal, methylglyoxal and glycolaldehyde and an increase in the abundance of ions associated with organic acids (e.g., oxalic and pyruvic acid) suggest that these aldehydes were present and reacting. The evidence is strongest for methylglyoxal (three RW samples). Glyoxal oxidation appears to occur in two RW samples; evidence for glycolaldehyde is not as strong. Other potential contributors to SOA formation (precursor and products) were identified based on their percentage of change and absolute change in ion abundance across the reaction.

Chemistry of Secondary Organic Aerosol

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ISBN 13 :
Total Pages : 466 pages
Book Rating : 4.:/5 (98 download)

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Book Synopsis Chemistry of Secondary Organic Aerosol by : Lindsay Diana Yee

Download or read book Chemistry of Secondary Organic Aerosol written by Lindsay Diana Yee and published by . This book was released on 2013 with total page 466 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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. Three 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. The 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.

Chemical and Physical Investigation of Secondary Organic Aerosol Formation

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ISBN 13 :
Total Pages : 188 pages
Book Rating : 4.:/5 (829 download)

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Book Synopsis Chemical and Physical Investigation of Secondary Organic Aerosol Formation by : Shunsuke Nakao

Download or read book Chemical and Physical Investigation of Secondary Organic Aerosol Formation written by Shunsuke Nakao and published by . This book was released on 2012 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Formation and Aging of Secondary Organic Aerosol from Toluene

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ISBN 13 :
Total Pages : 13 pages
Book Rating : 4.:/5 (96 download)

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Book Synopsis Formation and Aging of Secondary Organic Aerosol from Toluene by :

Download or read book Formation and Aging of Secondary Organic Aerosol from Toluene written by and published by . This book was released on 2015 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Volatile Organic Compounds in the Atmosphere

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Publisher : John Wiley & Sons
ISBN 13 : 0470994150
Total Pages : 512 pages
Book Rating : 4.4/5 (79 download)

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Book Synopsis Volatile Organic Compounds in the Atmosphere by : Ralf Koppmann

Download or read book Volatile Organic Compounds in the Atmosphere written by Ralf Koppmann and published by John Wiley & Sons. This book was released on 2008-04-15 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: Every day, large quantities of volatile organic compounds (VOCs) are emitted into the atmosphere from both anthropogenic and natural sources. The formation of gaseous and particulate secondary products caused by oxidation of VOCs is one of the largest unknowns in the quantitative prediction of the earth’s climate on a regional and global scale, and on the understanding of local air quality. To be able to model and control their impact, it is essential to understand the sources of VOCs, their distribution in the atmosphere and the chemical transformations which remove these compounds from the atmosphere. In recent years techniques for the analysis of organic compounds in the atmosphere have been developed to increase the spectrum of detectable compounds and their detection limits. New methods have been introduced to increase the time resolution of those measurements and to resolve more complex mixtures of organic compounds. Volatile Organic Compounds in the Atmosphere describes the current state of knowledge of the chemistry of VOCs as well as the methods and techniques to analyse gaseous and particulate organic compounds in the atmosphere. The aim is to provide an authoritative review to address the needs of both graduate students and active researchers in the field of atmospheric chemistry research.