Aqueous-Phase Secondary Organic Aerosol and Organosulfate Formation in Atmospheric Aerosols: A Modeling Study

We have examined aqueous-phase secondary organic aerosol (SOA) and organosulfate (OS) formation in atmospheric aerosols using a photochemical box model with coupled gas-phase chemistry and detailed aqueous aerosol chemistry. SOA formation in deliquesced ammonium sulfate aerosol is highest under low-...

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Bibliographic Details
Published in:	Environmental science & technology Vol. 46; no. 15; pp. 8075 - 8081
Main Authors:	McNeill, V. Faye, Woo, Joseph L, Kim, Derek D, Schwier, Allison N, Wannell, Neal J, Sumner, Andrew J, Barakat, Joseph M
Format:	Journal Article
Language:	English
Published:	Washington, DC American Chemical Society 07-08-2012
Subjects:	Aerosols Applied sciences Aqueous solutions Atmosphere Atmospheric aerosols Atmospheric pollution Chemical compounds Environmental science Exact sciences and technology Models, Theoretical Organic chemicals Organic Chemicals - chemistry Pollutants physicochemistry study: properties, effects, reactions, transport and distribution Pollution Sulfur - chemistry Atmospheric chemistry Aqueous medium Box model Pollutant formation Organic sulfate Aerosols Secondary pollutant Air pollution Photochemical reaction Modeling Gaseous phase reaction Organic compounds
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Summary:	We have examined aqueous-phase secondary organic aerosol (SOA) and organosulfate (OS) formation in atmospheric aerosols using a photochemical box model with coupled gas-phase chemistry and detailed aqueous aerosol chemistry. SOA formation in deliquesced ammonium sulfate aerosol is highest under low-NO x conditions, with acidic aerosol (pH = 1) and low ambient relative humidity (40%). Under these conditions, with an initial sulfate loading of 4.0 μg m–3, 0.9 μg m–3 SOA is predicted after 12 h. Low-NO x aqueous-aerosol SOA (aaSOA) and OS formation is dominated by isoprene-derived epoxydiol (IEPOX) pathways; 69% or more of aaSOA is composed of IEPOX, 2-methyltetrol, and 2-methyltetrol sulfate ester. 2-Methyltetrol sulfate ester comprises >99% of OS mass (66 ng m–3 at 40% RH and pH 1). In urban (high-NO x ) environments, aaSOA is primarily formed via reversible glyoxal uptake, with 0.12 μg m–3 formed after 12 h at 80% RH, with 20 μg m–3 initial sulfate. OS formation under all conditions studied is maximum at low pH and lower relative humidities (<60% RH), i.e., when the aerosol is more concentrated. Therefore, OS species are expected to be good tracer compounds for aqueous aerosol-phase chemistry (vs cloudwater processing).
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0013-936X 1520-5851
DOI:	10.1021/es3002986