Download or read book Aerosol Formation from Gas phase Reactions of Ozone and Olefin in Presence of Sulfur Dioxide with List of References written by and published by . This book was released on 1974 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aerosol Formation from Gas Phase Reactions of Ozone and Olefin in the Presence of Sulfur Dioxide written by David Nicholas McNelis and published by . This book was released on 1974 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Monthly Catalog of United States Government Publications written by and published by . This book was released on 1975 with total page 2834 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Studies of Gas aerosol Reactions written by Anand Gupta and published by . This book was released on 1991 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Secondary Aerosol written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This project focused on studying trace gases that participate in chemical reactions that form atmospheric aerosols. Ammonium sulfate is a major constituent of these tiny particles, and one important pathway to sulfate formation is oxidation of dissolved sulfur dioxide by hydrogen peroxide in cloud, fog and rainwater. Sulfate aerosols influence the number and size of cloud droplets, and since these factors determine cloud radiative properties, sulfate aerosols also influence climate. Peroxide measurements, in conjunction with those of other gaseous species, can used to distinguish the contribution of in-cloud reaction to new sulfate aerosol formation from gas-phase nucleation reactions. This will lead to more reliable global climate models. We constructed and tested a new 4-channel fluorescence detector for airborne detection of peroxides. We integrated the instrument on the G-1 in January, 2006 and took a test flight in anticipation of the MAX-Mex field program, where we planned to fly under pressurized conditions for the first time. We participated in the 2006 Megacity Initiative: Local and Global Research Observations (MILAGRO) - Megacity Aerosol EXperiment Mexico City (MAX-Mex) field measurement campaign. Peroxide instrumentation was deployed on the DOE G-1 research aircraft based in Veracruz, and at the surface site at Tecamac University.

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 A Computational Approach to Understanding Aerosol Formation and Oxidant Chemistry in the Troposphere written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An understanding of the mechanisms and kinetics of aerosol formation and ozone production in the troposphere is currently a high priority because these phenomena are recognized as two major effects of energy-related air pollution. Atmospheric aerosols are of concern because of their effect on visibility, climate, and human health. Equally important, aerosols can change the chemistry of the atmosphere, in dramatic fashion, by providing new chemical pathways (in the condensed phase) unavailable in the gas phase. The oxidation of volatile organic compounds (VOCs) and inorganic compounds (e.g., sulfuric acid, ammonia, nitric acid, ions, and mineral) can produce precursor molecules that act as nucleation seeds. The U.S. Department of Energy (DOE) Atmospheric Chemistry Program (ACP) has identified the need to evaluate the causes of variations in tropospheric aerosol chemical composition and concentrations, including determining the sources of aerosol particles and the fraction of such that are of primary and secondary origin. In particular, the ACP has called for a deeper understanding into aerosol formation because nucleation creates substantial concentrations of fresh particles that, via growth and coagulation, influence the Earth's radiation budget. Tropospheric ozone is also of concern primarily because of its impact on human health. Ozone levels are controlled by NOx and by VOCs in the lower troposphere. The VOCs can be either from natural emissions from such sources as vegetation and phytoplankton or from anthropogenic sources such as automobiles and oil-fueled power production plants. The major oxidant for VOCs in the atmosphere is the OH radical. With the increase in VOC emissions, there is rising concern regarding the available abundance of HOx species needed to initiate oxidation. Over the last five years, there have been four field studies aimed at initial measurements of HOx species (OH and HO? radicals). These measurements revealed HOx levels that are two to four times higher than expected from the commonly assumed primary sources. Such elevated abundances of HOx imply a more photochemically active troposphere than previously thought. This implies that rates of ozone formation in the lower region of the atmosphere and the oxidation of SO? can be enhanced, thus promoting the formation of new aerosol properties. Central to unraveling this chemistry is the ability to assess the photochemical product distributions resulting from the photodissociation of by-products of VOC oxidation. We propose to use state-of-the-art theoretical techniques to develop a detailed understanding of the mechanisms of aerosol formation in multicomponent (mixed chemical) systems and the photochemistry of atmospheric organic species. The aerosol studies involve an approach that determines homogeneous gas-particle nucleation rates from knowledge of the molecular interactions that are used to define properties of molecular clusters. Over the past several years we developed Dynamical Nucleation Theory (DNT), a novel advance in the theoretical description of homogeneous gas-liquid nucleation, and applied it to gas-liquid nucleation of a single component system (e.g., water). The goal of the present research is to build upon these advances by extending the theory to multicomponent systems important in the atmosphere (such as clusters containing sulfuric acid, water, ions, ammonia, and organics). In addition, high-level ab initio electronic structure calculations will be used to unravel the chemical reactivity of the OH radical and water clusters.

Download or read book The Stratospheric Aerosol Layer written by Albert Welford Castleman and published by Springer. This book was released on 1982 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study of the Aerosol Formation Resulting from the Direct Reaction of Ammonia and Sulfur Dioxide written by James L. Vance and published by . This book was released on 1975 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Part One the Modified Moments Method written by Carl Joseph Blumstein and published by . This book was released on 1975 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many problems in theoretical chemistry and physics can be formulated in terms of density functions. It is often the case in such problems that the density itself is unknown, but that several power moments of it can be obtained. Modified moments, a generaliz- ation of power moments, can provide a powerful tool for the analysis of these cases. Part one of the dissertation is concerned with the computation and use of modified moments. Reasons for the introduction of modified moments are discussed and a procedure is given for transforming from power moments to modified moments. Methods are given for the computation of modified moments of the normal mode spectral densities of model harmonic solids. Then, using model harmonic solids as examples, a number of techniques which use modified moments to obtain approximate representations for densities are described . These techniques in- clude an orthogonal polynomial expansion, a rational approximation, and methods for discovering and using information about sin- gularites in density functions . It is shown that very accurate representations for densities with singularities can be obtained. In some problems the result is not the density itself, but rather some average over the density. Two methods are described for evaluating such averages using modified moments. The first of these methods is Gaussian quadratures. Modified moments have significant advantages over power moments when used in this well known method for obtaining rigorous bounds to averages. The second method is based on series expansions. While this method does not provide bounds, results can be obtained for some averages which are much more accurate than those from quadratures. In part two of the dissertation a new mechanism for gas phase ozone-olefin reactions is proposed. The mechanism involves biradical intermediates which can react in a variety of ways. One of the possible reaction modes corresponds to the Criegee mechanism originally proposed to explain solution ozonolysis and generally also accepted in the past for gas phase reactions. However, an examination of the gas phase data on ozone-olefin reactions and of the thermochemical and kinetic requirements for these reactions indicates that the Criegee reaction mode may, in some cases, be the least important of the various reaction possibilities. The other reaction possibilities involve intramolecular hydrogen abstractions and rearrangements in biradical intermediates. The proposed mechanism provides reasonable explanations for a number of unusual observations on gas phase ozone-olefin reactions. However a number of questions remain unanswered. An effort is made to clarify these questions and to propose experimental means for resolving them.

Download or read book Assessment of the Ozone and Aerosol Formation Potentials reactivities of Organic Compounds Over the Eastern United States written by Amir Hakami and published by . This book was released on 2003 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Laboratory Investigation of Organic Aerosol Formation from Aromatic Hydrocarbons written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Our work for this DOE funded project includes: (1) measurements of the kinetics and mechanism of the gas-phase oxidation reactions of the aromatic hydrocarbons initiated by OH; (2) measurements of aerosol formation from the aromatic hydrocarbons; and (3) theoretical studies to elucidate the OH-toluene reaction mechanism using quantum-chemical and rate theories.

Download or read book Chamber Studies of Secondary Organic Aerosol Formation written by Axel Metzger and published by . This book was released on 2008 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aqueous Reaction Kinetics and Secondary Organic Aerosol Formation from Atmospheric Phenol Oxidation written by Jeremy Daniel Smith and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic aerosols (OA) are a dominant fraction of particulate mass in the atmosphere, and much is secondary in nature. Secondary organic aerosol (SOA) is formed in the atmosphere from volatile organic compound precursors. Traditional SOA formation pathways involve primarily gas-phase processes: Oxidation reactions of organic gases result in low-volatility products that condense to the particulate phase, increasing aerosol mass. However, in recent years heterogeneous processes, including aqueous reactions, have gained more attention as gas-phase processes often fail to accurately predict observed mass loadings of aerosol in the atmosphere. Aqueous SOA formation is the result of a volatile organic species partitioning to the aqueous phase (clouds, fogs, aqueous aerosols), where they are chemically converted into a non-volatile species that remains in the particulate phase upon water evaporation. In this work we explore the aqueous chemical reaction kinetics and the SOA formation potential of phenols, which are released in large quantities from biomass combustion. Phenols are a broad class of organic compounds with intermediate volatilities (102 - 106 [mu]g m−3 at 20°C) and moderate to high Henry's Law Constants (103 - 109M atm−1), indicating significant partitioning to atmospheric aqueous phases. We begin in chapters 2 and 3 by investigating the aqueous oxidation of the compounds phenol (compound with formula C6H5OH), guaiacol (2-methoxyphenol), syringol (2,6-dimethoxyphenol), and three dihydroxybenzenes (catechol, resorcinol, hydroquinone). For each phenol we examined reactions with two oxidants: hydroxyl radical (*OH) and the triplet excited state of 3,4-dimethoxybenzaldehyde, which is also emitted from biomass combustion. Triplet excited states (3C*) have been widely studied in surface waters (oceans and lakes) but are a novel oxidation pathway in atmospheric aqueous phases. The precursors for triplet excited states are essentially brown carbon: organic molecules high amoutns of conjugation (or nitrogen hetero atoms) that can absorb solar radiation, resulting in an excited molecule with a high oxidative potential. We find that the 3C*-mediated aqueous oxidations of phenols are rapid and can dominate over *OH at low pH (

Download or read book Chemical Kinetics and Mechanisms of Unsaturated Organic Aerosol Oxidation written by Theodora Nah and published by . This book was released on 2014 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the heterogeneous oxidation of organic particulate matter ("aerosol") is an active area of current research in atmospheric and combustion chemistry. The chemical evolution of organic aerosol is complex and dynamic since it can undergo multiple oxidation reactions with gas phase oxidants to form a mixture of different generations of oxidation products that control the average aerosol mass and volatility. In many of these systems, hydrocarbon free radicals, formed by reaction with gas phase oxidants, play key roles as initiators, propagators and terminators of surface reactions. This dissertation presents a detailed study of the reaction kinetics and mechanisms of the heterogeneous oxidation of unsaturated organic aerosol, and aims to provide new molecular and mechanistic insights into the reaction pathways in heterogeneous organic aerosol oxidation. The heterogeneous oxidation of unsaturated fatty acid (oleic acid C18H34O2, linoleic acid C18H32O2 and linolenic acid C18H30O2) aerosol by hydroxyl (OH) radicals is first studied in Chapter 2 to explore how surface OH addition reactions initiate chain reactions that rapidly transform the chemical composition of unsaturated organic aerosol. Oleic acid, linoleic acid and linolenic acid have the same linear C18 carbon backbone structure with one, two and three C=C double bonds, respectively. By studying carboxylic acids with different numbers of C=C double bonds, the role that multiple reactive sites plays in controlling reaction rates can be observed. The kinetic parameter of interest in these studies is the effective uptake coefficient, defined as the number of particle phase unsaturated fatty acid molecules reacted per OH-particle collision. The effective uptake coefficients for the unsaturated fatty acids are larger than unity, providing clear evidence for particle-phase secondary chain chemistry. The effective uptake coefficients for the unsaturated fatty acids decrease with increasing O2 concentration, indicating that O2 promotes chain termination in the unsaturated fatty acid reactions. The kinetics and products of squalene (a C30 branched alkene with 6 C=C double bonds) oxidation are compared to that of the unsaturated fatty acids in Chapters 3 and 4 to understand how molecular structure and chemical functionality influence reaction rates and mechanisms. The squalene effective uptake coefficient, which is also larger than one, is smaller than that of linoleic acid and linolenic acid despite the larger number of C=C double bonds in squalene. In contrast to the unsaturated fatty acids, the squalene effective uptake coefficient increases with O2 concentration, indicating that O2 promotes chain propagation in the squalene reaction. Elemental and product analysis of squalene aerosol shows that O2 promotes particle volatilization in the squalene reaction, suggesting that fragmentation reactions are important when O2 is present in the OH oxidation of branched unsaturated organic aerosol. In contrast, elemental and product analysis of linoleic acid aerosol shows that O2 does not influence the rate of particle volatilization in the linoleic acid reaction, suggesting that O2 does not alter the relative importance of fragmentation reactions in the OH oxidation of linear unsaturated organic aerosol. Lastly, depending on the aerosol phase (e.g. solid and semi-solid) and the timescale for homogeneous mixing within the aerosol particle, the chemical composition may vary spatially within an aerosol particle. This necessitates the need for new techniques to characterize the interfacial chemical composition of aerosol particles. In the last portion of the dissertation, direct analysis in real time mass spectrometry (DART-MS) is used to analyze the surface chemical composition of nanometer-sized organic aerosol particles in real time at atmospheric pressure. By introducing a stream of aerosol particles in between the DART ionization source and the atmospheric pressure inlet of the mass spectrometer, the aerosol particles are exposed to a thermal flow of helium or nitrogen gas containing some fraction of metastable helium atoms or nitrogen molecules. In this configuration, the molecular constituents of organic aerosol particles are desorbed, ionized and detected with reduced molecular ion fragmentation, allowing for compositional identification. The reaction of ozone with sub-micron oleic acid particles is also measured to demonstrate the ability of DART-MS to identify products and quantify reaction rates in a heterogeneous reaction.

Download or read book The Kinetics and Mechanisms of the Gas phase Reactions of Ozone with Unsaturated Compounds written by David Johnson and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.