Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern US
Several models were used to describe the partitioning of ammonia, water, and organic compounds between the gas and particle phases for conditions in the southeastern US during summer 2013. Existing equilibrium models and frameworks were found to be sufficient, although additional improvements in...
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Copernicus Publications
2018-01-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://www.atmos-chem-phys.net/18/357/2018/acp-18-357-2018.pdf |
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record_format |
Article |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
H. O. T. Pye A. Zuend J. L. Fry G. Isaacman-VanWertz G. Isaacman-VanWertz S. L. Capps K. W. Appel H. Foroutan H. Foroutan L. Xu N. L. Ng N. L. Ng A. H. Goldstein A. H. Goldstein |
spellingShingle |
H. O. T. Pye A. Zuend J. L. Fry G. Isaacman-VanWertz G. Isaacman-VanWertz S. L. Capps K. W. Appel H. Foroutan H. Foroutan L. Xu N. L. Ng N. L. Ng A. H. Goldstein A. H. Goldstein Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern US Atmospheric Chemistry and Physics |
author_facet |
H. O. T. Pye A. Zuend J. L. Fry G. Isaacman-VanWertz G. Isaacman-VanWertz S. L. Capps K. W. Appel H. Foroutan H. Foroutan L. Xu N. L. Ng N. L. Ng A. H. Goldstein A. H. Goldstein |
author_sort |
H. O. T. Pye |
title |
Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern US |
title_short |
Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern US |
title_full |
Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern US |
title_fullStr |
Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern US |
title_full_unstemmed |
Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern US |
title_sort |
coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern us |
publisher |
Copernicus Publications |
series |
Atmospheric Chemistry and Physics |
issn |
1680-7316 1680-7324 |
publishDate |
2018-01-01 |
description |
Several models were used to describe the partitioning of ammonia,
water, and organic compounds between the gas and particle phases for
conditions in the southeastern US during summer 2013. Existing
equilibrium models and frameworks were found to be sufficient, although
additional improvements in terms of estimating pure-species vapor
pressures are needed. Thermodynamic model predictions were
consistent, to first order, with a molar ratio of ammonium to sulfate
of approximately 1.6 to 1.8 (ratio of ammonium to 2 × sulfate,
<i>R</i><sub>N∕2S</sub> ≈ 0.8 to 0.9) with approximately 70 % of
total ammonia and ammonium (NH<sub><i>x</i></sub>) in the particle. Southeastern
Aerosol Research and Characterization Network (SEARCH) gas and aerosol
and Southern Oxidant and Aerosol Study (SOAS) Monitor for AeRosols and
Gases in Ambient air (MARGA) aerosol measurements were consistent with these
conditions. CMAQv5.2 regional chemical transport model predictions
did not reflect these conditions due to a factor of 3 overestimate
of the nonvolatile cations. In addition, gas-phase ammonia was
overestimated in the CMAQ model leading to an even lower fraction of
total ammonia in the particle. Chemical Speciation Network (CSN) and
aerosol mass spectrometer (AMS) measurements indicated less ammonium
per sulfate than SEARCH and MARGA measurements and were inconsistent
with thermodynamic model predictions. Organic compounds were
predicted to be present to some extent in the same phase as inorganic
constituents, modifying their activity and resulting in a decrease in
[H<sup>+</sup>]<sub>air</sub> (H<sup>+</sup> in µg m<sup>−3</sup> air), increase in ammonia partitioning to the gas phase,
and increase in pH compared to complete organic vs. inorganic
liquid–liquid phase separation. In addition, accounting for nonideal
mixing modified the pH such that a fully interactive inorganic–organic
system had a pH roughly 0.7 units higher than predicted using traditional
methods (pH = 1.5 vs. 0.7). Particle-phase interactions of organic and
inorganic compounds were found to increase partitioning towards the
particle phase (vs. gas phase) for highly oxygenated (O : C ≥ 0.6)
compounds including several isoprene-derived tracers as well as
levoglucosan but decrease particle-phase partitioning for low O : C,
monoterpene-derived species. |
url |
https://www.atmos-chem-phys.net/18/357/2018/acp-18-357-2018.pdf |
work_keys_str_mv |
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doaj-d3422adb43704f36bc3ccf3f6a612e6d2020-11-24T23:15:13ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242018-01-011835737010.5194/acp-18-357-2018Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern USH. O. T. Pye0A. Zuend1J. L. Fry2G. Isaacman-VanWertz3G. Isaacman-VanWertz4S. L. Capps5K. W. Appel6H. Foroutan7H. Foroutan8L. Xu9N. L. Ng10N. L. Ng11A. H. Goldstein12A. H. Goldstein13National Exposure Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina, USADepartment of Atmospheric and Oceanic Sciences, McGill University, Montreal, Québec, CanadaDepartment of Chemistry, Reed College, Portland, Oregon, USADepartment of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USADepartment of Environmental Science, Policy, and Management, University of California, Berkeley, California, USACivil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, Pennsylvania, USANational Exposure Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina, USANational Exposure Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina, USADepartment of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USADepartment of Environmental Science and Engineering, California Institute of Technology, Pasadena, California, USASchool of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USASchool of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USADepartment of Environmental Science, Policy, and Management, University of California, Berkeley, California, USADepartment of Civil and Environmental Engineering, University of California, Berkeley, California, USASeveral models were used to describe the partitioning of ammonia, water, and organic compounds between the gas and particle phases for conditions in the southeastern US during summer 2013. Existing equilibrium models and frameworks were found to be sufficient, although additional improvements in terms of estimating pure-species vapor pressures are needed. Thermodynamic model predictions were consistent, to first order, with a molar ratio of ammonium to sulfate of approximately 1.6 to 1.8 (ratio of ammonium to 2 × sulfate, <i>R</i><sub>N∕2S</sub> ≈ 0.8 to 0.9) with approximately 70 % of total ammonia and ammonium (NH<sub><i>x</i></sub>) in the particle. Southeastern Aerosol Research and Characterization Network (SEARCH) gas and aerosol and Southern Oxidant and Aerosol Study (SOAS) Monitor for AeRosols and Gases in Ambient air (MARGA) aerosol measurements were consistent with these conditions. CMAQv5.2 regional chemical transport model predictions did not reflect these conditions due to a factor of 3 overestimate of the nonvolatile cations. In addition, gas-phase ammonia was overestimated in the CMAQ model leading to an even lower fraction of total ammonia in the particle. Chemical Speciation Network (CSN) and aerosol mass spectrometer (AMS) measurements indicated less ammonium per sulfate than SEARCH and MARGA measurements and were inconsistent with thermodynamic model predictions. Organic compounds were predicted to be present to some extent in the same phase as inorganic constituents, modifying their activity and resulting in a decrease in [H<sup>+</sup>]<sub>air</sub> (H<sup>+</sup> in µg m<sup>−3</sup> air), increase in ammonia partitioning to the gas phase, and increase in pH compared to complete organic vs. inorganic liquid–liquid phase separation. In addition, accounting for nonideal mixing modified the pH such that a fully interactive inorganic–organic system had a pH roughly 0.7 units higher than predicted using traditional methods (pH = 1.5 vs. 0.7). Particle-phase interactions of organic and inorganic compounds were found to increase partitioning towards the particle phase (vs. gas phase) for highly oxygenated (O : C ≥ 0.6) compounds including several isoprene-derived tracers as well as levoglucosan but decrease particle-phase partitioning for low O : C, monoterpene-derived species.https://www.atmos-chem-phys.net/18/357/2018/acp-18-357-2018.pdf |