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Title: A Computational Approach to Understanding Aerosol Formation and Oxidant Chemistry in the Troposphere

Abstract

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 bymore » 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.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
881691
Report Number(s):
PNNL-15772
2393; KP1303000; TRN: US200613%%147
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; AEROSOLS; AIR POLLUTION; ATMOSPHERIC CHEMISTRY; CHEMICAL COMPOSITION; CHEMISTRY; ELECTRONIC STRUCTURE; INORGANIC COMPOUNDS; MOLECULAR CLUSTERS; NITRIC ACID; ORGANIC COMPOUNDS; OXIDIZERS; POWER GENERATION; SULFURIC ACID; TROPOSPHERE; VOLATILE MATTER; Environmental Molecular Sciences Laboratory

Citation Formats

Francisco, Joseph S., Kathmann, Shawn M., Schenter, Gregory K., Dang, Liem X., Xantheas, Sotiris S., Garrett, Bruce C., Du, Shiyu, Dixon, David A., Bianco, Roberto, Wang, Shuzhi, Hynes, James T., Morita, Akihiro, and Peterson, Kirk A. A Computational Approach to Understanding Aerosol Formation and Oxidant Chemistry in the Troposphere. United States: N. p., 2006. Web. doi:10.2172/881691.
Francisco, Joseph S., Kathmann, Shawn M., Schenter, Gregory K., Dang, Liem X., Xantheas, Sotiris S., Garrett, Bruce C., Du, Shiyu, Dixon, David A., Bianco, Roberto, Wang, Shuzhi, Hynes, James T., Morita, Akihiro, & Peterson, Kirk A. A Computational Approach to Understanding Aerosol Formation and Oxidant Chemistry in the Troposphere. United States. doi:10.2172/881691.
Francisco, Joseph S., Kathmann, Shawn M., Schenter, Gregory K., Dang, Liem X., Xantheas, Sotiris S., Garrett, Bruce C., Du, Shiyu, Dixon, David A., Bianco, Roberto, Wang, Shuzhi, Hynes, James T., Morita, Akihiro, and Peterson, Kirk A. Tue . "A Computational Approach to Understanding Aerosol Formation and Oxidant Chemistry in the Troposphere". United States. doi:10.2172/881691. https://www.osti.gov/servlets/purl/881691.
@article{osti_881691,
title = {A Computational Approach to Understanding Aerosol Formation and Oxidant Chemistry in the Troposphere},
author = {Francisco, Joseph S. and Kathmann, Shawn M. and Schenter, Gregory K. and Dang, Liem X. and Xantheas, Sotiris S. and Garrett, Bruce C. and Du, Shiyu and Dixon, David A. and Bianco, Roberto and Wang, Shuzhi and Hynes, James T. and Morita, Akihiro and Peterson, Kirk A.},
abstractNote = {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.},
doi = {10.2172/881691},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Apr 18 00:00:00 EDT 2006},
month = {Tue Apr 18 00:00:00 EDT 2006}
}

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