Abstract View
Comprehensive Product Characterization in the OH Oxidation of Dimethyl Sulfide: Effects of RO2 Fates on Sulfur Distribution
QING YE, Matthew Goss, Jordan Krechmer, Yaowei Li, Francesca Majluf, Alexander Zaytsev, Joseph Roscioli, Manjula Canagaratna, Frank Keutsch, Colette L. Heald, Jesse Kroll, MIT
Abstract Number: 384
Working Group: Aerosol Chemistry
Abstract
The atmospheric oxidation of dimethyl sulfide (DMS) from the oceans is the major source of natural sulfate aerosol globally. However, many details of the oxidation mechanism remain poorly constrained, largely due to limitations in measuring the full suite of oxidation products.
Here, chamber experiments were performed to measure product formation from OH-initiated oxidation of DMS using a suite of advanced online instruments that measured a broad suite of gas-and aerosol-phase sulfur-containing compounds. Specifically, hydroperoxymethyl thioformate (HOOCH2SCHO, HPMTF), the recently discovered compound formed from the isomerization of methylthiomethylperoxy radical (CH3SCH2OO•), was identified and quantified. The isomerization rate constant of the methylthiomethylperoxy radical is estimated to be ~ 0.1 s-1. Experiments were conducted under high and low NO level and under different temperatures to explore the fates of RO2 on the distribution of sulfur products. Over the course of 18 h atmospheric-equivalent oxidation under low NO condition (sub-ppb level NO), HPMTF is the dominant S species followed by SO2. Under high NO conditions (~50 ppb NO) and after 2 h oxidation, HPMTF does not form and the S budget is dominated by particle-phase products namely sulfate and methane sulfonic acid. Under low NO conditions and lower temperature (10 C), HPMTF is still the major product formed from the abstraction channel while there is an increased fraction of products from the addition channel including DMSO and DMSO2. Lastly, the effective reaction rate coefficients of HPMTF and methyl thioformate with OH were also estimated.