Organosulfates in the polluted atmosphere: compositions, origins and formation mechanisms Ping Liu 1,2 , Xiang Ding 1 , Andrew R. Rickard 2 , Jacqui Hamilton 2 1 State Key Laboratory of Organic Geochemistry, Chinese Academy of Sciences, China, 2 Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, UK Organosulfates (OSs) are a class of organic compounds containing the sulfate functional group (R-OSO 3 H), which have a significant impact on regional air quality and global climate. OSs are unique markers for secondary organic aerosol (SOA) formation under polluted conditions. OSs are assumed to mainly form through multiphase reactions between acidic sulfate particles and organic vapors of anthropogenic and biogenic origin. At present, comprehensive knowledge of OSs formation and evolution processes in the polluted atmosphere is lacking. Besides secondary formation, primary emissions from industry and personal care products also contribute to atmospheric OSs, especially in urban areas. Therefore, it is critical to distinguish the primary and secondary sources of OSs. In-depth studies on OS formation would not only enrich our knowledge and scientific understanding of atmospheric chemical compositions, formation mechanisms and sources of OSs, but also provide critical information for the formulation of economically effective air pollution and climate control strategies. PM 2.5 filter samples collected at sites in Guangzhou (urban) and Tianhu (forest) were analysed, focusing on the diurnal variations of atmospheric OSs between urban and forest sites. Interactions of anthropogenic and biogenic emissions were explored to provide insights into OS and SOA formation under polluted conditions. Two isomers of the m/z 260 (C 5 H 10 NSO 9 − ) OS, which originates from the photooxidation of isoprene under high NO x conditions were observed. At both sites isomer 1 is higher during the day than at nighttime, whilst isomer 2 is higher at night than during the day. Future work will explore the day and nighttime chemical pathways responsible for this specific observation. A second OS studied in detail was m/z 265 (C 12 H 25 SO 4 − ), a long-chain alkane-derived OS, which may have a range of different sources, e.g. traffic, biomass burning, wastewater, and ocean transport. They are also used in industry and personal care products. In this study, the concentration of C 12 H 25 SO 4 − is higher in the urban environment compared to the forest site. The diurnal profile indicates it is mainly of second generation origin owing to correlations with ozone. However, a series of long-chain alkane OSs were detected in cleaning products, which may be a major primary source of C 12 H 25 SO 4 − . Future work will explore specific primary and secondary source proportions of C 12 H 25 SO 4 − , aiding understanding of SOA formation in urban areas with high concentrations of OSs. References 1. Gomez, G.Y., et al. (2008), Journal Of Mass Spectrometry . 43, 371-382. 2. Hettiyadura, A. P. S., et al. (2015), Atmospheric Measurement Techniques. 8, 2347-2358.
3. Surratt, J.D., et al. (2008), Journal Of Physical Chemistry A. 112, 8345 – 8378. 4. Blair, S.L., et al. (2017), Environmental science & technology . 51, 119– 127.
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