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

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• 作者：V. Faye McNeill ; Joseph L. Woo ; Derek D. Kim ; Allison N. Schwier ; Neal J. Wannell ; Andrew J. Sumner ; Joseph M. Barakat
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：August 7, 2012
• 年：2012
• 卷：46
• 期：15
• 页码：8075-8081
• 全文大小：321K
• 年卷期：v.46,no.15(August 7, 2012)
• ISSN：1520-5851

文摘

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 渭g m^鈥?, 0.9 渭g m^鈥? 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^鈥? at 40% RH and pH 1). In urban (high-NO_x) environments, aaSOA is primarily formed via reversible glyoxal uptake, with 0.12 渭g m^鈥? formed after 12 h at 80% RH, with 20 渭g m^鈥? 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).