Aqueous Hydroxyl Radical (OH) Oxidation of Organosulfates

SURBHI GUPTA, Tran Nguyen, University of California, Davis

     Abstract Number: 637
     Working Group: Aerosol Chemistry

Abstract
Organosulfates (R-OSO3H), ubiquitous in atmospheric aerosols, are either formed in the atmosphere from aqueous chemistry or are directly released during biomass burning. Both the formation routes of organosulfates (OS) and their ability to react away during their long residence time in the atmosphere are areas of active study. Recent work in our group shows that the isoprene organosulfate has a relatively fast aqueous-phase reaction rate coefficient with hydroxyl radicals (OH). The heterogeneous OH oxidation of OS has been proposed to release the sulfate radical anion (SO4·−) alongside fragment products including smaller OS; however, a number of open questions remain regarding the fate of the sulfur moiety. As the reactive SO4·− is quenched by water to generate bisulfate ions and OH radicals, providing direct evidence of their formation in the aqueous phase is challenging. Our study investigates the aqueous photooxidation of organosulfates with OH radicals, focusing on stable product formation mechanisms and the potential radical propagation of SO4·−, which is capable of performing further cascade reactions with available reactive centers. Various OS with different chemical structures are tested. Analysis of the products is carried out with Nuclear Magnetic Resonance (NMR) and untargeted High Performance Liquid Chromatography coupled to High Resolution Mass Spectrometry (HPLC-HRMS).