An advanced modeling study on the impacts and atmospheric implications of multiphase dimethyl sulfide chemistry

Erik Hans Hoffmann, Peter Bräuer, Roland Schrödner, Ralf Wolke, Hartmut Herrmann

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Oceans dominate emissions of dimethyl sulfide (DMS), the major natural sulfur source.DMSis important for the formation of non-sea salt sulfate (nss-SO42−) aerosols and secondary particulate matter over oceans and thus, significantly influence global climate. The mechanism of DMS oxidation has accordingly been investigated in several different model studies in the past. However, these studies had restricted oxidation mechanisms that mostly underrepresented important aqueous-phase chemical processes. These neglected but highly effective processes strongly impact direct product yields of DMS oxidation, thereby affecting the climatic influence of aerosols. To address these shortfalls, an extensivemultiphase DMS chemistry mechanism, the Chemical Aqueous Phase Radical Mechanism DMS Module 1.0, was developed and used in detailed model investiga- tions of multiphase DMS chemistry in the marine boundary layer. The performed model studies confirmed the importance of aqueous- phase chemistry for the fate of DMS and its oxidation products. Aqueous-phase processes significantly reduce the yield of sulfur di- oxide and increase that of methyl sulfonic acid (MSA),which is needed to close the gap between modeled and measured MSA concentra- tions. Finally, the simulations imply that multiphase DMS oxidation produces equal amounts of MSA and sulfate, a result that has sig- nificant implications for nss-SO42− aerosol formation, cloud con-
densation nuclei concentration, and cloud albedo over oceans. Our findings show the deficiencies of parameterizations currently used in higher-scale models, which only treat gas-phase chemis- try. Overall, this study shows that treatment of DMS chemistry in both gas and aqueous phases is essential to improve the accuracy of model predictions.
Original languageEnglish
Pages (from-to)11776-11781
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number42
Early online date29 Sept 2016
Publication statusPublished - 18 Oct 2016

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