Significant Conversion of Organic Sulfur from Hydroxymethanesulfonate to Inorganic Sulfate and Peroxydisulfate Ions upon Heterogeneous OH Oxidation

Hydroxymethanesulfonate (CH2(OH)SO3 (-), HMS) has been found to be an important organosulfurcompound inatmospheric aerosols. However, its atmospheric fate is largely uncertain.In this work, we investigated the heterogeneous OH oxidation of HMSusing an oxidation flow reactor. In particular, we examined the rateand chemistry of the sulfur conversion from its organic form to itsinorganic counterparts upon oxidation by quantifying HMS and inorganicsulfur species (i.e., sulfate (SO4 (2-))and peroxydisulfate (S2O8 (2-)) ions) by using ion chromatography. Kinetic data show that OH oxidationof HMS can proceed efficiently with an effective OH uptake coefficient,& gamma;( eff ) of 0.35 & PLUSMN; 0.03. Upon oxidation,the formation of SO4 (2-) and S2O8 (2-) can explain the aerosol sulfurconversion. An aerosol sulfur mass closure was also obtained by quantifyingthe amount of HMS, SO4 (2-), and S2O8 (2-) before and after oxidation. Kineticmodel simulations show that reaction kinetics and product formationcan be well explained by a series of aerosol-phase chain reactionsinitiated by the sulfite radical anion (SO3 (& BULL;-)) under our experimental conditions. Overall, our results highlighta significant conversion of organic sulfur from HMS to inorganic sulfurspecies, including S2O8 (2-) uponheterogeneous OH oxidation.