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Author: James Freeman Hunter
Publisher:
ISBN:
Category :
Languages : en
Pages : 110
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Book Description
.Organic molecules have many important roles in the atmosphere, acting as climate and biogeochemical forcers, and in some cases as toxic pollutants. The lifecycle of atmospheric organic carbon is extremely complex, with reaction in multiple phases (gas, particle, aqueous) and at multiple timescales. The details of the lifecycle chemistry (especially the amount and properties of particles) have important implications for air quality, climate, and human and ecosystem health, and need to be understood better. Much of the chemical complexity and uncertainty lies in the reactions and properties of low-volatility oxidized intermediates that result from the oxidation of volatile organic precursors, and which have received comparatively little study thus far. This thesis describes three projects that link together the entire chain of oxidation (volatile to intermediate to condensed) in an effort to improve our understanding of carbon lifecycle and aerosol production. Laboratory studies of atmospherically relevant aerosol precursors show that the slow oxidation of intermediates is critical to explaining the yield and properties of aerosol under highly oxidized ("aged") conditions, and that the production of organic particles is significantly increased when intermediates are fully oxidized. This aging process is a strong function of molecular structure, and depends on aerosol concentration through the phenomenon of condensational trapping. Further laboratory studies of a series of (poly)cyclic 10 carbon alkanes show that structural effects are largely explained through fragmentation reactions, and that more generally, carbon-carbon bond scission is a ubiquitous and important reaction channel for oxidized intermediates. Finally, direct measurement of oxidized intermediate compounds in field studies shows that these compounds are abundant and important in the ambient atmosphere, with concentrations and properties in between those of volatile and particulate organic compounds. Together with other co-located measurements and complementary techniques, this enables estimates of emission, oxidation, and deposition to be constructed. The results from this thesis can be used to inform more sophisticated models of atmospheric organic carbon cycling, and to improve prediction of organic particulate matter concentrations.
Author: James Freeman Hunter
Publisher:
ISBN:
Category :
Languages : en
Pages : 110
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Book Description
.Organic molecules have many important roles in the atmosphere, acting as climate and biogeochemical forcers, and in some cases as toxic pollutants. The lifecycle of atmospheric organic carbon is extremely complex, with reaction in multiple phases (gas, particle, aqueous) and at multiple timescales. The details of the lifecycle chemistry (especially the amount and properties of particles) have important implications for air quality, climate, and human and ecosystem health, and need to be understood better. Much of the chemical complexity and uncertainty lies in the reactions and properties of low-volatility oxidized intermediates that result from the oxidation of volatile organic precursors, and which have received comparatively little study thus far. This thesis describes three projects that link together the entire chain of oxidation (volatile to intermediate to condensed) in an effort to improve our understanding of carbon lifecycle and aerosol production. Laboratory studies of atmospherically relevant aerosol precursors show that the slow oxidation of intermediates is critical to explaining the yield and properties of aerosol under highly oxidized ("aged") conditions, and that the production of organic particles is significantly increased when intermediates are fully oxidized. This aging process is a strong function of molecular structure, and depends on aerosol concentration through the phenomenon of condensational trapping. Further laboratory studies of a series of (poly)cyclic 10 carbon alkanes show that structural effects are largely explained through fragmentation reactions, and that more generally, carbon-carbon bond scission is a ubiquitous and important reaction channel for oxidized intermediates. Finally, direct measurement of oxidized intermediate compounds in field studies shows that these compounds are abundant and important in the ambient atmosphere, with concentrations and properties in between those of volatile and particulate organic compounds. Together with other co-located measurements and complementary techniques, this enables estimates of emission, oxidation, and deposition to be constructed. The results from this thesis can be used to inform more sophisticated models of atmospheric organic carbon cycling, and to improve prediction of organic particulate matter concentrations.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
A detailed understanding of the sources, transformations, and fates of organic species in the environment is crucial because of the central roles that organics play in human health, biogeochemical cycles, and Earth's climate. However, such an understanding is hindered by the immense chemical complexity of environmental mixtures of organics; for example, atmospheric organic aerosol consists of at least thousands of individual compounds, all of which likely evolve chemically over their atmospheric lifetimes. Here we demonstrate the utility of describing organic aerosol (and other complex organic mixtures) in terms of average carbon oxidation state (OSC), a quantity that always increases with oxidation, and is readily measured using state-of-the-art analytical techniques. Field and laboratory measurements of OSC, using several such techniques, constrain the chemical properties of the organics and demonstrate that the formation and evolution of organic aerosol involves simultaneous changes to both carbon oxidation state and carbon number (nC).
Author: Ralf Koppmann
Publisher: John Wiley & Sons
ISBN: 0470994150
Category : Science
Languages : en
Pages : 512
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Book Description
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.
Author: E.M. Thurman
Publisher: Springer Science & Business Media
ISBN: 9789024731435
Category : Science
Languages : en
Pages : 524
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Book Description
This book is written as a reference on organic substances in natural waters and as a supplementary text for graduate students in water chemistry. The chapters address five topics: amount, origin, nature, geochemistry, and characterization of organic carbon. Of these topics, the main themes are the amount and nature of dissolved organic carbon in natural waters (mainly fresh water, although seawater is briefly discussed). It is hoped that the reader is familiar with organic chemistry, but it is not necessary. The first part of the book is a general overview of the amount and general nature of dissolved organic carbon. Over the past 10 years there has been an exponential increase in knowledge on organic substances in water, which is the result of money directed toward the research of organic compounds, of new methods of analysis (such as gas chromatography and mass spectrometry), and most importantly, the result of more people working in this field. Because of this exponential increase in knowledge, there is a need to pull together and summarize the data that has accumulated from many disciplines over the last decade.
Author: John R Barker
Publisher: World Scientific
ISBN: 9813271841
Category : Science
Languages : en
Pages : 616
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Book Description
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.
Author: Jack G Calvert
Publisher: Oxford University Press
ISBN: 0199710880
Category : Science
Languages : en
Pages : 1005
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Book Description
An international team of eminent atmospheric scientists have prepared Mechanisms of Atmospheric Oxidation of the Alkanes as an authoritative source of information on the role of alkanes in the chemistry of the atmosphere. The book includes the properties of the alkanes and haloalkanes, as well as a comprehensive review and evaluation of the existing literature on the atmospheric chemistry of the alkanes and their major atmospheric oxidation products, and the various approaches now used to model the alkane atmospheric chemistry. Comprehensive coverage is given of both the unsubstituted alkanes and the many haloalkanes. All the existing quality measurements of the rate coefficients for the reactions of OH, Cl, O(3P), NO3, and O3 with the alkanes, the haloalkanes, and their major oxidation products have been reviewed and evaluated. The expert authors then give recommendations of the most reliable kinetic data. They also review the extensive literature on the mechanisms and rates and modes of photodecomposition of the haloalkanes and the products of atmospheric oxidation of the alkanes and the haloalkanes, and make recommendations for future use by atmospheric scientists. The evaluations presented allow an extrapolation of the existing kinetic and photochemical data to those alkanes and haloalkanes that are as yet unstudied. The current book should be of special interest and value to the modelers of atmospheric chemistry as a useful input for development of realistic modules designed to simulate the atmospheric chemistry of the alkanes, their major oxidation products, and their influence on ozone and other trace gases within the troposphere.
Author: Hermann Bothe
Publisher: Elsevier
ISBN: 0444531084
Category :
Languages : en
Pages : 451
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Book Description
Author: Christopher Yung-Ta Lim
Publisher:
ISBN:
Category :
Languages : en
Pages : 101
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Book Description
Fine particulate matter (PM, or "aerosol") in the atmosphere affects the Earth's radiative balance and is one of the most important risk factors leading to premature mortality worldwide. Thus, understanding the processes that control the loading and chemical composition of PM in the atmosphere is key to understanding air quality and climate. However, the chemistry of organic aerosol (OA), which comprises a significant fraction of submicron atmospheric PM, is immensely complex due to the vast number of organic compounds in the atmosphere and their numerous reaction pathways. Laboratory experiments have generally focused on the initial formation of OA from volatile organic compounds (VOCs), but have neglected processes that can change the composition and loading of OA over longer timescales ("aging"). This thesis describes several laboratory studies that better constrain the effect of two important aging processes over timescales of several days, the oxidation of gas phase species to form secondary OA (condensation) and the reaction of gas phase radicals with organic molecules in the particle phase (heterogeneous oxidation). First, the oxidation of biomass burning emissions is studied by exposing particles and gases present in smoke to hydroxyl radicals (OH). Increases in organic aerosol mass are observed for all fuels burned, and the amount of OA formed is explained well by the extent of aging and the total concentration of measured organic gases. Second, the effect of particle morphology on the rate of heterogeneous oxidation is examined by comparing the oxidation of particles with thin organic coatings to the oxidation of pure organic particles. Results show that morphology can have a strong impact on oxidation kinetics and that particles with high organic surface area to volume ratios can be rapidly oxidized. Third, the molecular products from the heterogeneous OH oxidation of a single model compound (squalane) are measured. Formation of a range of gas-phase oxygenated VOCs is observed, indicating the importance of fragmentation reactions that decrease OA mass, and providing insight into heterogeneous reaction mechanisms. The results from this work emphasize that the concentration and composition of OA can change dramatically over multiple days of atmospheric oxidation.
Author: Delphis F. Levia
Publisher: Springer Science & Business Media
ISBN: 9400713630
Category : Science
Languages : en
Pages : 734
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Book Description
This international rigorously peer-reviewed volume critically synthesizes current knowledge in forest hydrology and biogeochemistry. It is a one-stop comprehensive reference tool for researchers and practitioners in the fields of hydrology, biogeoscience, ecology, forestry, boundary-layer meteorology, and geography. Following an introductory chapter tracing the historical roots of the subject, the book is divided into the following main sections: · Sampling and Novel Approaches · Forest Hydrology and Biogeochemistry by Ecoregion and Forest Type · Hydrologic and Biogeochemical Fluxes from the Canopy to the Phreatic Surface · Hydrologic and Biogeochemical Fluxes in Forest Ecosystems: Effects of Time, Stressors, and Humans The volume concludes with a final chapter that reflects on the current state of knowledge and identifies some areas in need of further research.
Author: Joshua Alexandre Moss
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Volatile Organic Compounds (VOCs) oxidize in the troposphere and significantly influence the formation of pollutants including ground-level ozone, CO2, and particulate matter (PM). Ozone and PM negatively impact human health, and all three pollutants influence Earth's climate. VOCs also dominate the OH reactivity of the atmosphere which in turn influences concentrations of other important radical species including NO[subscript x] and HO2. Chamber experiments are often conducted to measure VOC oxidation in a controlled laboratory setting, but these studies are may be complicated by vapor deposition on chamber surfaces and potential VOC decomposition in the Chemical Ionization Mass Spectrometers (CIMS) which are used to measure a broad range of oxidation products. Mechanistic simulations are also frequently performed to emulate chamber chemistry with less effort and fewer complications than may arise during a chamber experiment, but the results of these simulations are limited by uncertainties and gaps in our understanding of VOC oxidation chemistry from empirical studies. This thesis addresses uncertainties in chamber measurements and mechanisms and uses both in tandem to provide mutual benefits. Chapter 2 focuses on the development and characterization of a Total Suspended Carbon (TSC) apparatus which may be used to parametrize chamber vapor deposition.
