Formation of Particulate Organic Matter; Some Observations and Implications PDF Download

Author: Stephen Randall Jones
Publisher:
ISBN:
Category : Chemistry, Organic
Languages : en
Pages : 160

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Author: Jonathan H. Sharp
Publisher: 1972 [c1974]
ISBN:
Category :
Languages : en
Pages : 0

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Author: Gerard Roland Miller
Publisher:
ISBN:
Category : Seawater
Languages : en
Pages : 214

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Author: National Research Council
Publisher: National Academies Press
ISBN: 0309144019
Category : Nature
Languages : en
Pages : 248

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Recent advances in air pollution monitoring and modeling capabilities have made it possible to show that air pollution can be transported long distances and that adverse impacts of emitted pollutants cannot be confined to one country or even one continent. Pollutants from traffic, cooking stoves, and factories emitted half a world away can make the air we inhale today more hazardous for our health. The relative importance of this "imported" pollution is likely to increase, as emissions in developing countries grow, and air quality standards in industrial countries are tightened. Global Sources of Local Pollution examines the impact of the long-range transport of four key air pollutants (ozone, particulate matter, mercury, and persistent organic pollutants) on air quality and pollutant deposition in the United States. It also explores the environmental impacts of U.S. emissions on other parts of the world. The book recommends that the United States work with the international community to develop an integrated system for determining pollution sources and impacts and to design effective response strategies. This book will be useful to international, federal, state, and local policy makers responsible for understanding and managing air pollution and its impacts on human health and well-being.

Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 1740

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Author: Anthony Joseph Carrasquillo
Publisher:
ISBN:
Category :
Languages : en
Pages : 113

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Atmospheric particulate matter (or "aerosol") has important implications for public health, climate change, and visibility. Our ability to predict its formation and fate is hindered by uncertainties associated with one type in particular, organic aerosol (OA). The study of the chemistry underlying OA formation is complicated by the large number of reaction pathways and oxidation generations for a given precursor species. This thesis describes a series of experiments in which the chemistry is simplified to that of a single alkoxy radical (RO) isomer generated from the direct photolysis of alkyl nitrites (RONO). First, OA was generated from eleven different C10 RO isomers to determine the role of radical molecular structure in the formation of low-volatility species. Here, measured aerosol yields and chemical composition were explained by two major effects: (1) the relative importance of isomerization and fragmentation pathways, which control the distribution of products, and (2) differences in saturation vapor pressure of individual isomers. Next, we developed a method to investigate the reactivity of alkoxy radicals in the condensed phase. The long chain C20 RO radical was generated in hexane solvent to identify possible intermolecular (bimolecular) reactions with the condensed-phase. The lack of formation of the C20 alcohol, the expected product of the bimolecular reaction of RO with hexane indicates that these intermolecular reactions are unable to compete with available unimolecular isomerization processes. Finally, a molecular-level study of this same condensed-phase system with a soft ionization technique permitted the observation of molecular ions that are assigned to specific oxidation products. This approach enables the determination of the extent of branching for another important intermediate, the alkylperoxy radical. The results from this thesis highlight the role of radical structure in the formation of low-volatility products in the atmosphere, in addition to identifying the major reaction pathways responsible for particle-phase oxidative processing.

Author: Robert A. Baker
Publisher: CRC Press
ISBN: 9780873715287
Category : Technology & Engineering
Languages : en
Pages : 564

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The fate and transport of natural and anthropogenic sediment-borne organic contaminants is a critical environmental issue and complex processes are involved that until now have been poorly defined. Organic Substances and Sediments in Water is a three-volume book that provides the best information available regarding the many interdisciplinary factors affecting organic substances associated with particulates in water. Topics discussed include absorption and transport of contaminants associated with particles; interfacial processes affecting fate and transport of organic substances associated with particles; the release of contaminants in receiving water bodies; water treatment; the role of biological factors in the fate and transport of organic contaminants in aqueous systems; development of biotransformation in natural and anthropogenic systems; the use of organic contaminant and sediment chemicals; biological and physical data to refine models to be used by resource managers; and chemical and biological processes that affect the fate and transport of organic constituents and determine degradation of contaminants and uptake in plants. This will be an important reference for environmental chemists, environmental engineers, environmental biologists, water treatment and natural system modelers, and soils scientists.

Author: Roy Chester
Publisher: John Wiley & Sons
ISBN: 1444311573
Category : Science
Languages : en
Pages : 522

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Book Description
The first edition of Marine Geochemistry received strongcritical acclaim, and the reviews included the comments that it'provides a benchmark in the field' and 'is clearly recognizable asa standard text for years to come'. Marine Geochemistry offers a fully comprehensive andintegrated treatment of the chemistry of the oceans, theirsediments and biota. It addresses the fundamental question 'How dothe oceans work as a chemical system?' by capitalizing on thesignificant advances in understanding oceanic processes made overthe past three decades. These advances have been facilitated byimproved sampling and analytical techniques, a better understandingof theoretical concepts and the instigation of large-sizedinternational oceanographic programs. Designed for use as a text, the book treats the oceans as a'unified system' in which material stored in the sea water, thesediment and the rock reservoirs interacts to control thecomposition of sea water itself. Part I covers the transport ofmaterial to the oceans via rivers, the atmosphere and hydrothermalsystems, and discusses their relative flux magnitudes. Part IIconsiders the oceans as a reservoir, introducing water-columnparameters before discussing water-column fluxes and the benthicboundary layer. Part III is devoted to the sediment reservoir. Thetopics covered include diagenesis, the major components of thesediments, and the processes controlling the geochemistry ofoceanic deposit, which are discussed in terms of sediment-formingsignals. Part IV offers an overview and synthesis of the integratedmarine geochemical system. Since the publication of the first edition, there have beenfurther significant advances in several areas of the subject. Therevised text of this edition accommodates these advances, whilestill retaining the emphasis on identifying key processes operatingwithin a 'unified ocean.' Special attention has been paid tofundamental conceptual changes, such as those related to tracemetal speciation in sea water, hydrothermal activity, carbondioxide and the importance of the oceans in world climate change,the transport of particulate material to the interior of the ocean,primary production and iron limitation, colloids, and thepreservation/destruction of organic matter in marine sediments. Intermediate and advanced students with interests in chemicaloceanography, marine geochemistry, marine biology and environmentalchemistry will welcome this revised comprehensive text. Otherstudents in the broader field of earth sciences will find it to bean essential reference source dealing with the interaction betweenthe atmosphere, the ocean and the solid earth. Incorporates all significant recent advances in thefield. 'Unified system' approach to ocean chemistry. Emphasises geological contexts, e.g. sediment diagenesis.

Author: Katheryn Ruth Kolesar
Publisher:
ISBN: 9781339261232
Category :
Languages : en
Pages :

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Atmospheric particulate matter (PM) is a component of air pollution that negatively impacts human health and welfare and has strong impacts on global climate. The organic fraction of PM, organic aerosol (OA), is often a dominant fraction of PM mass. Organic aerosol can be emitted directly into the atmosphere as primary OA (POA) or can be produced in the atmosphere from processes such as gas phase reactions of volatile organic compounds (VOCs) with oxidants or aqueous phase reactions of dissolved organics both of which form secondary OA (SOA). The formation and evolution of SOA, as well as the interaction between SOA and POA, are poorly characterized, which leads to uncertainties in the prediction of their concentrations and impacts in the atmosphere. This dissertation addresses processes associated with gas phase SOA formation as well as chemical and physical processing of SOA and POA through experimental studies investigating: 1) the volatility of SOA, 2) the influence of SOA on the heterogeneous oxidation of POA, and 3) the chemical mechanisms of POA oxidation. In the first set of studies (Chapters 2-3), it is experimentally demonstrated that there has been a fundamental disconnect between the properties of SOA as derived from SOA formation and growth experiments and those derived from evaporation experiments, which has implications for the representation of SOA within air quality and climate models. Specifically, SOA is experimentally determined to be less volatile than predicted based on formation studies through the measurement of the extent of evaporation with temperature change along with concurrent measurement of the particle composition. Volatility measurements were made as a function of mass concentration for [alpha]pinene+O3 SOA and with accompanying particle composition measurements for different SOA types. It was found that SOA volatility was independent of mass concentration and that nine types of SOA had similar volatilities. Furthermore, SOA composition remained constant as particles evaporated. When compared to results from a detailed, physically based model of evaporation, these observations suggest that there are condensed-phase chemical reactions that rapidly produce oligomers and that oligomers are likely the majority of the SOA mass. In a second study (Chapter 4), a detailed experimental and model assessment of the chemical pathways associated with OH-driven heterogeneous chemistry of two model POA compounds is discussed. The chemical pathways for oxidation of POA are often assumed to be the same as gas phase reactions, yet the higher density of molecules in the condensed phase may increase the dominance of alternate mechanisms. The heterogeneous oxidation of squalane and BES are used as model POA compounds to investigate structure-dependent chemical mechanisms of oxidation. The oxidation of squalane is dominated by the formation of products with added ketone or alcohol functionality whereas the oxidation of BES is dominated by the addition of ketone moieties with minor contributions from pathways forming alcohol substituted products. These differences are shown to be linked directly to differences in the dominant chemical pathways available to the different precursor molecules that result from structural differences in the molecules. In Chapter 5, the influence of an SOA "coating" on the OH initiated heterogeneous oxidation of model POA particles, comprised of squalane, is considered. Previous studies have shown that SOA can protect buried compounds from reaction with O3 but the extent to which such protection extends to other oxidants had not been established. Here, it is shown that when OH is the oxidant SOA does not block squalane from oxidation and, in fact, the rate of oxidation with OH exposure is enhanced. Although it is clear that an enhancement occurs, the exact extent of enhancement is dependent on the assumed particle morphology, i.e. whether the particle is well mixed, partially engulfed or there is an SOA coating on the squalane core.

Author: Youliang Wang
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 111

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The atmosphere contains a substantial amount of water soluble organic material, yet despite years of efforts, little is known about the structure, composition and properties of this organic matter. Aqueous phase processing by fogs and clouds of the gas and particulate organic material is poorly understood despite the importance for air pollution and climate. On one hand, gas phase species can be processed by fog/cloud droplets to form lower volatility species, which upon droplet evaporation lead to new aerosol mass; while, on the other hand, larger nonvolatile material can be degraded in cloud oxidation to smaller molecular weight compounds and eventually CO2. In this work, High Performance Size Exclusion Chromatography coupled with inline organic carbon detection (SEC-DOC), Diffusion-Ordered Nuclear Magnetic Resonance spectroscopy (DOSY-NMR) and Fluorescence Excitation-Emission Matrices (EEM) were used to characterize molecular weight distribution, functionality and optical properties of atmospheric organic matter. Fogs, aerosols and clouds were studied in a variety of environments including Central Valley of California (Fresno, Davis), Pennsylvania (Selinsgrove), British Columbia (Whistler) and three locations in Norway. The molecular weight distributions using SEC-DOC showed smaller molecular sizes for atmospheric organic matter compared to surface waters and a smaller material in fogs and clouds compared to aerosol particles, which is consistent with a substantial fraction of small volatile gases that partition into the aqueous phase. Both cloud and aerosol samples presented a significant fraction (up to 21% of DOC) of biogenic nanoscale material. The results obtained by SEC-DOC were consistent with DOSY-NMR observations. Cloud processing of organic matter has also been investigated by combining field observations (sample time series) with laboratory experiments under controlled conditions. Observations revealed no significant effect of aqueous phase chemistry on molecular weight distributions overall although during cloud events, substantial differences were apparent between organic material activated into clouds compared to interstitial material. Optical properties, on the other hand, showed significant changes including photobleaching and an increased humidification of atmospheric material by photochemical aging. Overall, any changes to atmospheric organic matter during cloud processing were small in terms of bulk carbon properties, consistent with recent reports suggesting fogs and clouds are too dilute to substantially impact composition.