Journal article
Coupling of organic and inorganic aerosol systems and the effect on gas-particle partitioning in the southeastern US
Atmospheric chemistry and physics, v 18(1), pp 357-370
12 Jan 2018
PMID: 29963078
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
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,
≈ 0.8 to 0.9) with approximately 70% of total ammonia and ammonium (NH
) 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
]
(H
in μgm
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 levoglu-cosan but decrease particle-phase partitioning for low O: C, monoterpene-derived species.
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Details
- Title
- Coupling of organic and inorganic aerosol systems and the effect on gas-particle partitioning in the southeastern US
- Creators
- Havala O T Pye - National Exposure Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina, USAAndreas Zuend - Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Québec, CanadaJuliane L Fry - Department of Chemistry, Reed College, Portland, Oregon, USAGabriel Isaacman-VanWertz - Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USAShannon L Capps - Civil, Architectural, and Environmental Engineering, Drexel University, Philadelphia, Pennsylvania, USAK Wyat Appel - National Exposure Research Laboratory, US Environmental Protection Agency, Research Triangle Park, North Carolina, USAHosein Foroutan - Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USALu Xu - Department of Environmental Science and Engineering, California Institute of Technology, Pasadena, California, USANga L Ng - School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USAAllen H Goldstein - Department of Civil and Environmental Engineering, University of California, Berkeley, California, USA
- Publication Details
- Atmospheric chemistry and physics, v 18(1), pp 357-370
- Publisher
- Germany
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Civil, Architectural, and Environmental Engineering
- Web of Science ID
- WOS:000419987100002
- Scopus ID
- 2-s2.0-85040726134
- Other Identifier
- 991014877953904721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Environmental Sciences
- Meteorology & Atmospheric Sciences