2-Methyltetrol Sulfate Oxidation by Hydroxyl Radical in Fog and Cloud Water Mimics and Its Implications for the Fate of Isoprene-Derived Secondary Organic Aerosol
HALEY ROYER, Ashley Harrill, Cade Christensen, Yuzhi Chen, Zhenfa Zhang, Avram Gold, Andrew Ault, Barbara Turpin, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 257
Working Group: Carbonaceous Aerosols
Abstract
2-Methyltetrol sulfate diastereomers (2-MTS) are the single most-abundant SOA tracers in atmospheric fine particulate matter (PM2.5). In isoprene-rich regions, multiphase IEPOX chemistry converts inorganic sulfate aerosol to organosulfates such as 2-MTS, making 2-MTS a major constituent of SOA mass. Though 2-MTS is pervasive within SOA, its fate in the atmosphere is still poorly understood. While recent studies have explored its sinks within deliquesced aerosol, 2-MTS has also been observed in cloud water, rainwater, hailstones, and snow, and its sinks within these atmospheric waters is unknown. In a series of controlled batch reactor experiments, we explore the oxidation of 2-MTS in fog and cloud water mimics to determine the second-order rate constant of 2-MTS oxidation against aqueous hydroxyl radicals (•OH). A decrease in 2-MTS concentrations and increase in reaction products were observed using hydrophilic interaction liquid chromatography interfaced to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (HILIC/ESI-HR-QTFOMS). Samples were also analyzed using ion chromatography (IC) to corroborate mass spectrometry measurements of 2-MTS as well as to determine changes to inorganic sulfate concentrations. Results also include an estimated second-order rate constant for both cloud and fog water concentrations of 2-MTS and •OH. as well as proposed reaction products and reaction mechanisms for 2-MTS oxidation. These findings ultimately have implications for the composition, physical properties, and behavior of IEPOX-derived SOA.