Formation of particulate organosulfates under different atmospheric conditions in polluted Beijing, China
Abstract
Organosulfates (OSs) with ambiguous formation mechanisms could be a substantial source of "missing urban SOA" in current atmospheric models, resulting in underestimation of SOA or prediction with large uncertainties. Intensive field observations were conducted in winter and summer at both regional and urban sites in Beijing, aiming to gain understanding of the OS formation and influence factors under different atmospheric conditions. Particulate OSs, including hydroxycarboxylic acid sulfates, isoprene OSs and monoterpene OSs, were comprehensively characterized, with additional data of inorganic compositions, particle properties, VOC and gaseous precursors.
The OS concentrations were highest in summer at the regional site due to the higher biogenic emissions and favorable environmental conditions (e.g. higher RH and particle acidity) for OS formation, and lowest in winter at the urban site otherwise. Acid-catalyzed aqueous-phase reactions in the presence of sulfate particles represent important formation pathways of OSs in Beijing. The acidic particle properties, with predicted pH 2.7-5.9, provided suitable conditions for the OS formation via acid-catalyzed reactions. The elevated inorganic sulfate was more capable to promote the OSs formation in summer than in winter, which could be attributed to the more abundant biogenic VOC precursors to react with sulfate and the favorable conditions for OS formation in summer. The low RH in winter was a limiting factor for the OS formation via aqueous-phase reaction pathways. This work provides direct observational evidence for gaining insights into the formation and influence factors of OSs under the interaction of VOC precursors and anthropogenic pollutants (e.g. SO42-, SO2, NOx). The results imply the importance of future reduction in anthropogenic SO2 and NOx emissions to reduce the SOA burden in Beijing and also in polluted environments with abundant biogenic emissions and anthropogenic pollutants.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A24B..06W
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0317 Chemical kinetic and photochemical properties;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE