10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

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Reactions between SO2 and Organic Peroxides and Their Role as Atmospheric Sinks of Sulfur

SHUNYAO WANG, Shouming Zhou, Ye Tao, Jianhuai Ye, Jian Zhen Yu, Jennifer G. Murphy, Jonathan Abbatt, Arthur W. H. Chan, University of Toronto

     Abstract Number: 1102
     Working Group: Aerosol Chemistry

Abstract
While SO2 oxidation has long been recognized as a source of particulate sulfate and acid rain, the underlying mechanisms by which SO2 reacts with multiple organic species remain poorly understood. Previous chamber studies have shown that organic peroxides from monoterpene ozonolysis can react with SO2, suggesting that organic peroxides (ROOR or ROOH) could be an important sink of SO2. In this work, we investigate the kinetics and mechanisms of reactions between SO2 and organic peroxides. Upon SO2 exposure in a bulk solution, the depletion of both ROOR and ROOH standards (including cumene hydroperoxide, tert-butyl hydroperoxide, 2-butanone peroxide, benzoyl peroxide and tert-butyl peroxide) was monitored using iodometric-spectrophotometric method and was found to be significant. The reaction rate constant will be derived from the decay of total S (IV) concentration (monitored by ion chromatography) and speciated organic peroxide concentration (monitored by atmospheric pressure chemical ionization tandem mass spectrometry). In addition to the formation of inorganic sulfate, organosulfates (OS) were also formed, and were quantified by electrospray ionization ion mobility mass spectrometry (ESI-IMS) under negative mode with collision induced dissociation, using both synthetic biogenic OS and commercial OS as calibration standards. In addition to bulk solution studies, we also conduct flow tube experiments to study the reactive uptake coefficients (γeff) for SO2 and biogenic SOA (i.e. α-pinene, isoprene). Measured kinetic parameters can be further applied to the atmospheric models to assess the potential impacts. Our work will improve understanding of how the interaction between SO2 and organic peroxides will influence the formation of biogenic SOA under atmospheric-relevant conditions.