Conversion of Organic Sulfur from Hydroxymethanesulfonate (HMS) to Inorganic Sulfur Species upon Heterogeneous OH Oxidation

Donger Lai, Yee Ka Wong, Rongshuang Xu, Sinan Xing, Sze In Madeleine Ng, Lin Kong, Jian Zhen Yu, Dan Dan Huang, MAN NIN CHAN, The Chinese University of Hong Kong

     Abstract Number: 156
     Working Group: Aerosol Chemistry

Abstract
Hydroxymethanesulfonate (HMS) has been found to be an important organosulfur compound in atmospheric aerosols. Recent laboratory studies have revealed heterogeneous OH oxidation of organosulfur compounds can generate inorganic sulfates. However, reaction kinetics, products and mechanisms for such sulfur conversion from its organic form to inorganic counterparts upon oxidation of organosulfur compounds remain unclear. We investigated the heterogeneous OH oxidation of sodium hydroxymethanesulfonate (Na-HMS) using an oxidation flow reactor (OFR) by measuring the decay of HMS and the formation of inorganic sulfur species upon oxidation using ion chromatography (IC). Kinetic data show that the oxidation is efficient with an effective OH uptake coefficient, γeff of 0.35 ± 0.03. The conversion from organic sulfur from HMS into inorganic sulfur species can be well accounted by the formation of bisulfate, sulfate, and peroxydisulfate upon oxidation. A kinetic model is developed to simulate the formation and evolution of reaction products during oxidation. Model results suggest that the decay of HMS and the formation of inorganic sulfur species can be well explained by a series of aerosol-phase chain reactions triggered by sulfite anion radical. Overall, our results suggest a significant conversion of organic sulfur from HMS to inorganic sulfur species, in particular peroxydisulfate ion upon heterogeneous OH oxidation.