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Sources, Chemistry, and Transport of Urban Aerosols and Oxidized Mercury: An Analysis Combining Aircraft and Surface Observations with a Chemical Transport Model.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Sources, Chemistry, and Transport of Urban Aerosols and Oxidized Mercury: An Analysis Combining Aircraft and Surface Observations with a Chemical Transport Model./
作者:	Shah, Viral Pinakin.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
面頁冊數:	190 p.
附註:	Source: Dissertations Abstracts International, Volume: 80-02, Section: B.
Contained By:	Dissertations Abstracts International80-02B.
標題:	Atmospheric Chemistry. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10828153
ISBN:	9780438176423

Sources, Chemistry, and Transport of Urban Aerosols and Oxidized Mercury: An Analysis Combining Aircraft and Surface Observations with a Chemical Transport Model.
Shah, Viral Pinakin.

Sources, Chemistry, and Transport of Urban Aerosols and Oxidized Mercury: An Analysis Combining Aircraft and Surface Observations with a Chemical Transport Model. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 190 p.

Source: Dissertations Abstracts International, Volume: 80-02, Section: B.

Thesis (Ph.D.)--University of Washington, 2018.

This item must not be added to any third party search indexes.

I examine of the sources, chemistry, and transport of aerosol particles and oxidized mercury compounds in the atmosphere using aircraft- and ground-based observations and a global chemical transport model. In Chapter 2, I use extensive airborne observations of atmospheric composition over the eastern U.S. from the 2015 Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER) campaign, ground-based observations, and the GEOS-Chem chemical transport model, to determine the controls on winter SO42- and NO3- . The model reproduces observed concentrations of total SO42--NO 3- -NH4+ particulates (2.45 μg sm-3) and their composition (SO42-: 47%, NO3- : 32%, NH4+: 21%) during WINTER. I find that the wintertime oxidation efficiency of SO 2 to SO42- in the eastern U.S. is limited by low [H2O2] and [OH]. Relatively acidic fine particulates (pH~1.3) allow 45% of the total nitrate to partition to the particle phase. Between the 2007 and 2015 simulations, SO2 emissions decreased by 58%, but simulated [H2O2] remained constant, causing an increase in the simulated SO2 oxidation efficiency to SO 42-. Simulated NOx emissions decreased by 35%, but the NO3- particle fraction increased as fine particle acidity decreased. These feedbacks resulted in a 40% decrease of [SO42-] and no change in [NO3- ]. [SO4 2-] and [NO3- ] will change slowly between 2015 and 2023, unless SO2 and NOx emissions decrease faster in the future than in the recent past. In Chapter 3, I analyze the wintertime emissions and secondary formation of organic aerosols (OA) over the northeastern U.S. with observations from the WINTER aircraft campaign and ground-based monitoring sites, and three OA modeling approaches in GEOS-Chem. The observed OA concentrations below 1 km during WINTER were 1.48 μg sm-3. Factor analysis of the observations indicate that secondary OA (SOA) contributed 60% and primary OA (POA) 40%. I reproduce the WINTER OA, POA, and SOA observations using an empirical parameterization for SOA from urban emissions and POA emissions from the National Emissions Inventory (NEI) reduced by half, suggesting that the NEI overestimates primary wintertime OA emissions. The simulation captures the observed OA growth from the photochemical formation of SOA, and reproduces ground-based OA measurements. The traditional approach, which includes SOA from oxidation of C6-C8 aromatics, predicts almost no SOA. The approach that includes SOA from the oxidation of low-volatility gases emitted initially as POA underestimates POA by a factor of 5. I find that OA are regionally distributed and account for 35% of the fine particulates over the NE US during WINTER. Wintertime OA over the region is overwhelmingly anthropogenic, with 23% from residential wood combustion emissions and 63% from secondary sources. In Chapter 4, I use the GEOS-Chem model to quantify how surface deposition of Hg(II) is influenced by oxidized mercury (Hg(II)) production at different atmospheric heights. GEOS-Chem reproduces ground- and aircraft-based observations of Hg(II) reasonably well. Hg(II) produced above 750 hPa constitutes 91% of the tropospheric mass of Hg(II) and 77% of the global Hg(II) deposition flux. This is because of fast chemical production and slow loss of Hg(II) at these altitudes. I assess the effects of the main sources of model uncertainty (oxidant concentrations, oxidation pathways, and emissions speciation) with additional simulations, and find similarly large contribution of Hg(II) produced above 750 hPa to the tropospheric Hg(II) mass (78-90%) and to the global Hg(II) surface deposition flux (57-76%). I find that 55% of the spatial variation of Hg wet deposition flux observed at the ground-based sites in the U.S. is explained by the combined variation of precipitation and Hg(II) produced above 750 hPa. Hg(II) present in the subtropical anticyclones accounts for 74% of Hg(II) at 500 hPa and about 60% at the surface over the continental U.S. Hg(II) produced in the upper and middle troposphere subsides in the anticyclones, where the dry conditions inhibit the loss of Hg(II), which make these anticyclones important for Hg cycling in the atmosphere.

ISBN: 9780438176423Subjects--Topical Terms:

1669583
Atmospheric Chemistry.
Subjects--Index Terms:

Mercury

Sources, Chemistry, and Transport of Urban Aerosols and Oxidized Mercury: An Analysis Combining Aircraft and Surface Observations with a Chemical Transport Model.
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500 $a Source: Dissertations Abstracts International, Volume: 80-02, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
500 $a Advisor: Jaegle, Lyatt.
502 $a Thesis (Ph.D.)--University of Washington, 2018.
506 $a This item must not be added to any third party search indexes.
506 $a This item must not be sold to any third party vendors.
520 $a I examine of the sources, chemistry, and transport of aerosol particles and oxidized mercury compounds in the atmosphere using aircraft- and ground-based observations and a global chemical transport model. In Chapter 2, I use extensive airborne observations of atmospheric composition over the eastern U.S. from the 2015 Wintertime Investigation of Transport, Emissions, and Reactivity (WINTER) campaign, ground-based observations, and the GEOS-Chem chemical transport model, to determine the controls on winter SO42- and NO3- . The model reproduces observed concentrations of total SO42--NO 3- -NH4+ particulates (2.45 μg sm-3) and their composition (SO42-: 47%, NO3- : 32%, NH4+: 21%) during WINTER. I find that the wintertime oxidation efficiency of SO 2 to SO42- in the eastern U.S. is limited by low [H2O2] and [OH]. Relatively acidic fine particulates (pH~1.3) allow 45% of the total nitrate to partition to the particle phase. Between the 2007 and 2015 simulations, SO2 emissions decreased by 58%, but simulated [H2O2] remained constant, causing an increase in the simulated SO2 oxidation efficiency to SO 42-. Simulated NOx emissions decreased by 35%, but the NO3- particle fraction increased as fine particle acidity decreased. These feedbacks resulted in a 40% decrease of [SO42-] and no change in [NO3- ]. [SO4 2-] and [NO3- ] will change slowly between 2015 and 2023, unless SO2 and NOx emissions decrease faster in the future than in the recent past. In Chapter 3, I analyze the wintertime emissions and secondary formation of organic aerosols (OA) over the northeastern U.S. with observations from the WINTER aircraft campaign and ground-based monitoring sites, and three OA modeling approaches in GEOS-Chem. The observed OA concentrations below 1 km during WINTER were 1.48 μg sm-3. Factor analysis of the observations indicate that secondary OA (SOA) contributed 60% and primary OA (POA) 40%. I reproduce the WINTER OA, POA, and SOA observations using an empirical parameterization for SOA from urban emissions and POA emissions from the National Emissions Inventory (NEI) reduced by half, suggesting that the NEI overestimates primary wintertime OA emissions. The simulation captures the observed OA growth from the photochemical formation of SOA, and reproduces ground-based OA measurements. The traditional approach, which includes SOA from oxidation of C6-C8 aromatics, predicts almost no SOA. The approach that includes SOA from the oxidation of low-volatility gases emitted initially as POA underestimates POA by a factor of 5. I find that OA are regionally distributed and account for 35% of the fine particulates over the NE US during WINTER. Wintertime OA over the region is overwhelmingly anthropogenic, with 23% from residential wood combustion emissions and 63% from secondary sources. In Chapter 4, I use the GEOS-Chem model to quantify how surface deposition of Hg(II) is influenced by oxidized mercury (Hg(II)) production at different atmospheric heights. GEOS-Chem reproduces ground- and aircraft-based observations of Hg(II) reasonably well. Hg(II) produced above 750 hPa constitutes 91% of the tropospheric mass of Hg(II) and 77% of the global Hg(II) deposition flux. This is because of fast chemical production and slow loss of Hg(II) at these altitudes. I assess the effects of the main sources of model uncertainty (oxidant concentrations, oxidation pathways, and emissions speciation) with additional simulations, and find similarly large contribution of Hg(II) produced above 750 hPa to the tropospheric Hg(II) mass (78-90%) and to the global Hg(II) surface deposition flux (57-76%). I find that 55% of the spatial variation of Hg wet deposition flux observed at the ground-based sites in the U.S. is explained by the combined variation of precipitation and Hg(II) produced above 750 hPa. Hg(II) present in the subtropical anticyclones accounts for 74% of Hg(II) at 500 hPa and about 60% at the surface over the continental U.S. Hg(II) produced in the upper and middle troposphere subsides in the anticyclones, where the dry conditions inhibit the loss of Hg(II), which make these anticyclones important for Hg cycling in the atmosphere.
590 $a School code: 0250.
650 4 $a Atmospheric Chemistry. $3 1669583
650 4 $a Atmospheric sciences. $3 3168354
653 $a Mercury
653 $a Oxidized mercury
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710 2 $a University of Washington. $b Atmospheric Sciences. $3 3174193
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