Coupling of organic and inorganic aerosol systems and the effect on gas-particle partitioning in the southeastern US

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dc.contributor.authorPye, Havala O. T.en
dc.contributor.authorZuend, Andreasen
dc.contributor.authorFry, Juliane L.en
dc.contributor.authorIsaacman-VanWertz, Gabrielen
dc.contributor.authorCapps, Shannon L.en
dc.contributor.authorAppel, K. Wyaten
dc.contributor.authorForoutan, Hoseinen
dc.contributor.authorXu, Luen
dc.contributor.authorNg, Nga L.en
dc.contributor.authorGoldstein, Allen H.en
dc.contributor.departmentCivil and Environmental Engineeringen
dc.contributor.departmentBiomedical Engineering and Mechanicsen
dc.date.accessioned2019-11-21T14:35:35Zen
dc.date.available2019-11-21T14:35:35Zen
dc.date.issued2018-01-12en
dc.description.abstractSeveral 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 x sulfate, R-N/2S approximate to 0.8 to 0.9) with approximately 70% of total ammonia and ammonium (NHx) 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+](air) (H+ in mu g m(-3) 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.en
dc.description.notesWe thank J. Jimenez, G. Ruggeri, S. Takahama, and S. Lee for providing additional data sets that are summarized in the supporting information. We thank the CSN and SEARCH networks for providing long-term measurements. We thank the two reviewers at the EPA. We thank Paul Solomon for useful discussion. We thank CSRA for preparing emissions and meteorology input for CMAQ simulations. Andreas Zuend was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), grant RGPIN/04315-2014. Juliane L. Fry acknowledges support from EPA-STAR RD-83539901. Gabriel Isaacman-VanWertz was supported by the NSF Graduate Research Fellowship (DGE 1106400). F<INF>p</INF> of organic compounds collected by SV-TAG at SOAS was supported by grants to UC Berkeley, including NSF Atmospheric Chemistry Program 1250569 and Department of Energy SBIR grant DE-SC0004698. Lu Xu and Nga L. Ng acknowledge support from National Science Foundation (NSF) grant 1242258 and US Environmental Protection Agency (EPA) STAR grant RD-83540301.en
dc.description.sponsorshipNatural Sciences and Engineering Research Council of Canada (NSERC)Natural Sciences and Engineering Research Council of Canada [RGPIN/04315-2014]; EPA-STARUnited States Environmental Protection Agency [RD-83539901]; NSFNational Science Foundation (NSF) [DGE 1106400]; NSF Atmospheric Chemistry ProgramNational Science Foundation (NSF) [1250569]; National Science Foundation (NSF)National Science Foundation (NSF) [1242258]; US Environmental Protection Agency (EPA) STARUnited States Environmental Protection Agency [RD-83540301]; Department of Energy SBIR grant [DE-SC0004698]en
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.5194/acp-18-357-2018en
dc.identifier.eissn1680-7324en
dc.identifier.issn1680-7316en
dc.identifier.issue1en
dc.identifier.urihttp://hdl.handle.net/10919/95828en
dc.identifier.volume18en
dc.language.isoenen
dc.publisherEuropean Geophysical Unionen
dc.rightsCreative Commons Attribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.titleCoupling of organic and inorganic aerosol systems and the effect on gas-particle partitioning in the southeastern USen
dc.title.serialAtmospheric Chemistry and Physicsen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten
dc.type.dcmitypeStillImageen

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