Download or read book Formation Ageing and Thermal Properties of Secondary Organic Aerosol Elektronisk Resurs written by and published by . This book was released on 2013 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Formation and Aging of Secondary Organic Aerosol from Alpha pinene Oxidation written by Kaytlin Henry and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Formation and Degradation of Secondary Organic Aerosol Material written by Alison Mariko Fankhauser and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We utilize the current state of knowledge surrounding IEPOX SOA formation in an attempt to elucidate a unifying mechanism. However, model results suggest that significant gaps remain in our understanding of formation and aging processes, especially oligomerization. Finally, we consider microbial consumption of aerosol organics in the atmosphere. Observations of culturable cells in aqueous aerosols and cloud water suggest that they may be actively metabolizing aqueous media while they are airborne, which could have significant impacts on aerosol and cloud properties. Metabolic rates of cells cultured from atmospheric samples are incorporated into GAMMA. While there is a substantial decrease in the concentration of organic species for particles in which cells reside, the overall effect on populations of particles is negligible, and bacterial metabolism is not expected to measurably alter the organic content of the atmosphere.

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:

Download or read book Laboratory Studies on the Formation of Secondary Organic Aerosol from the Atmospheric Oxidation of Alkenes written by Kenneth Stephen Docherty and published by . This book was released on 2004 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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:

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:

Download or read book Phase Partitioning During the Formation of Secondary Organic Aerosol written by Chen Wang and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A sound parameterization of the gas-particle partitioning process is essential for understanding and quantifying secondary organic aerosol (SOA) formation. This thesis aimed to improve the understanding and description of phase partitioning during SOA formation through a combination of both laboratory and modeling studies. Partitioning of organic compounds between gas and particle phase is influenced by the presence of a large quantity of inorganic salts in aerosol, which is known as the salt effect. The salt effects of atmospherically relevant inorganic salts for a large number of organic compounds with various functional groups were measured in this study. The results revealed the importance of both salt species and organic compound identities on the salt effect, with the former as the dominant determinant. Models in predicting salt effect were calibrated and evaluated using the experimental data. Salt effect in mixtures was also investigated, which assists the understanding of salt effect in mixture salt solutions, including aerosols. A new approach for predicting gas-particle partitioning during SOA formation based on quantum chemical calculations was presented, which considers the partitioning species explicitly and captures the dynamic aspects of the aerosol formation processes. The role of different atmospheric parameters and chemical properties (organic loading, liquid water content, salinity, chemical ageing, etc.) was investigated and compared. Performance of the model was found to be comparable to the best currently used group contribution methods. SOA formation from constant emission and oxidation of precursor compounds was simulated to resemble the realistic scenario in the ambient atmosphere. The differential yield that describes the amount of SOA formed from a certain amount of added oxidation products was introduced, which is more relevant for SOA formation in the ambient atmosphere. The necessity of considering kinetic processes in addition to the thermodynamic equilibrium process was also discussed.

Download or read book The Influence of Formation Temperature on Secondary Organic Aerosol Volatility written by Katherine Smith and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The volatility of secondary organic aerosol (SOA) formed from the dark ozonolysis of [alpha]-pinene in a flow tube at temperatures ranging from 275 to 298 K has been characterized by thermally induced evaporation. The SOA was heated from the formation temperature (T[subscript f]) in a thermodenuder and the temperature-dependent volume loss was measured. The resulting thermograms for the SOA formed at the different temperatures were nearly identical when considered as a function of [delta]T (= T – T[subscript f]), rather than absolute temperature. A kinetic model of aerosol evaporation was used to derive T[subscript f]-specific effective volatility distributions for the SOA. The derived distributions indicate SOA formed at lower temperatures is composed of compounds having higher effective volatilities compared to that formed at higher temperatures. However, the increased abundance of compounds having higher effective volatilities at lower T[subscript f] cannot be explained solely due to increased partitioning into the particle phase due to a decrease in vapor pressures. Instead, much of the dependence on T[subscript f] likely results from T-dependent changes in the fraction of the particles that is monomers versus dimers (or higher order oligomers). The relatively short formation time (

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:

Download or read book Secondary Organic Aerosol Formation from Select Volatile Organic Compounds written by Chia-Li Chen and published by . This book was released on 2015 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis enhances our understanding of secondary organic aerosol (SOA) formation from select anthropogenic sources including polycyclic aromatic hydrocarbons (PAHs), PAHs mixed with m -xylene and an atmospheric surrogate, and unburned whole gasoline vapors. Major SOA chemical characteristics and physical properties were explored along with SOA formation within the UCR CE-CERT environmental chamber.

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.

Download or read book Formation of Biogenic Secondary Organic Aerosol written by Qi Chen and published by . This book was released on 2011 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.

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.

Download or read book Modeling Global Secondary Organic Aerosol Formation and Processing with the Volatility Basis Set written by Salvatore Farina and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Inorganic Thermodynamics Acid catalyzed Secondary Organic Aerosol Formation and Aerosol Crystallization written by Satoshi Takahama and published by . This book was released on 2005 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: