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Author: Wayne Li-wen Chang
Publisher:
ISBN: 9781124262932
Category :
Languages : en
Pages : 44
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Book Description
Secondary organic aerosol (SOA) comprises a significant portion of atmospheric particular matter (PM). The impact of PM on both human health and global climate has long been recognized. Despite its importance, there are still many unanswered questions regarding the formation and evolution of SOA in the atmosphere. This study uses a modeling approach to understand the preferred partitioning behavior of SOA species into aqueous or organic condensed phases. More specifically, this work uses statistical analyses of approximately 24,000 data values for each variable from a state-of-the-art 3-D airshed model. Spatial and temporal distributions of fractions of SOA residing in the aqueous phase (fAQ) in the South Coast Air Basin of California are presented. Typical values of fAQ within the basin near the surface range from 5 to 80%. Results show that the distribution of fAQ values is inversely proportional to the total SOA loading. Further analysis accounting for various meteorological parameters indicates that large fAQ values are the results of aqueous-phase SOA insensitivity to the ambient conditions; while organic-phase SOA concentrations are dramatically reduced under unfavorable SOA formation conditions, aqueous-phase SOA level remains relatively unchanged, thus increasing fAQ at low SOA loading. Diurnal variations of fAQ near the surface are also observed: it tends to be larger during daytime hours than nighttime hours. When examining the vertical gradient of fAQ, largest values are found at heights above the surface layer. In summary, one must consider SOA in both organic and aqueous phases for proper regional and global SOA budget estimation.
Author: Wayne Li-wen Chang
Publisher:
ISBN: 9781124262932
Category :
Languages : en
Pages : 44
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Book Description
Secondary organic aerosol (SOA) comprises a significant portion of atmospheric particular matter (PM). The impact of PM on both human health and global climate has long been recognized. Despite its importance, there are still many unanswered questions regarding the formation and evolution of SOA in the atmosphere. This study uses a modeling approach to understand the preferred partitioning behavior of SOA species into aqueous or organic condensed phases. More specifically, this work uses statistical analyses of approximately 24,000 data values for each variable from a state-of-the-art 3-D airshed model. Spatial and temporal distributions of fractions of SOA residing in the aqueous phase (fAQ) in the South Coast Air Basin of California are presented. Typical values of fAQ within the basin near the surface range from 5 to 80%. Results show that the distribution of fAQ values is inversely proportional to the total SOA loading. Further analysis accounting for various meteorological parameters indicates that large fAQ values are the results of aqueous-phase SOA insensitivity to the ambient conditions; while organic-phase SOA concentrations are dramatically reduced under unfavorable SOA formation conditions, aqueous-phase SOA level remains relatively unchanged, thus increasing fAQ at low SOA loading. Diurnal variations of fAQ near the surface are also observed: it tends to be larger during daytime hours than nighttime hours. When examining the vertical gradient of fAQ, largest values are found at heights above the surface layer. In summary, one must consider SOA in both organic and aqueous phases for proper regional and global SOA budget estimation.
Author: Chen Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
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.
Author: Christopher James Hennigan
Publisher:
ISBN:
Category : Air
Languages : en
Pages :
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Book Description
This thesis characterizes properties of ambient secondary organic aerosol (SOA), an important and abundant component of particulate matter. The findings presented in this thesis are significant because they represent the results from ambient measurements, which are relatively scarce, and because they report on properties of SOA that, until now, were highly uncertain. The analyses utilized the fraction of particulate organic carbon that was soluble in water (WSOCp) to approximate SOA concentrations in two largely different urban environments, Mexico City and Atlanta. In Mexico City, measurements of atmospheric gases and fine particle chemistry were made at a site ~ 30 km down wind of the city center. Using box model analyses and a comparison to ammonium nitrate aerosol, a species whose thermodynamic properties are generally understood, the morning formation and mid-day evaporation of SOA are investigated. In Atlanta, simultaneous measurements of WSOCp and water-soluble organic carbon in the gas phase (WSOCg) were carried out for an entire summer to investigate the sources and partitioning of WSOC. The results suggest that both WSOCp and WSOCg were secondary and biogenic, except possibly in several strong biomass burning events. The gas/particle partitioning of WSOC in Atlanta was investigated through the parameter, Fp, which represented the fraction of WSOC in the particle phase. Factors that appear to influence WSOC partitioning in Atlanta include ambient relative humidity and the WSOCp mass concentration. There was also a relationship between the NOx concentration and Fp, though this was not likely related to the partitioning process. Temperature did not appear to impact Fp, though this may have been due to positive relationships WSOCp and WSOCg each exhibited with temperature. Neither the total Organic Carbon aerosol mass concentration nor the ozone concentration impacted WSOC partitioning.
Author:
Publisher: ScholarlyEditions
ISBN: 1464963479
Category : Science
Languages : en
Pages : 5241
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Book Description
Issues in General Science and Scientific Theory and Method: 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about General Science and Scientific Theory and Method. The editors have built Issues in General Science and Scientific Theory and Method: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about General Science and Scientific Theory and Method in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in General Science and Scientific Theory and Method: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.
Author: Keri B. Leach
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 134
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Book Description
Author: Xiaohui Huang
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 201
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Book Description
Author: Bethany A. Warren
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 414
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Book Description
Author: Chen Song
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 532
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Book Description
Author: Jay Russell Odum
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 246
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Book Description
Author: Donald Mackay
Publisher: CRC Press
ISBN: 9781566706872
Category : Science
Languages : en
Pages : 1000
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Book Description
Transport and transformation processes are key for determining how humans and other organisms are exposed to chemicals. These processes are largely controlled by the chemicals’ physical-chemical properties. This new edition of the Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals is a comprehensive series in four volumes that serves as a reference source for environmentally relevant physical-chemical property data of numerous groups of chemical substances. The handbook contains physical-chemical property data from peer-reviewed journals and other valuable sources on over 1200 chemicals of environmental concern. The handbook contains new data on the temperature dependence of selected physical-chemical properties, which allows scientists and engineers to perform better chemical assessments for climatic conditions outside the 20–25-degree range for which property values are generally reported. This second edition of the Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals is an essential reference for university libraries, regulatory agencies, consultants, and industry professionals, particularly those concerned with chemical synthesis, emissions, fate, persistence, long-range transport, bioaccumulation, exposure, and biological effects of chemicals in the environment. This resource is also available on CD-ROM
