AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Organic Hydroperoxides (ROOH) Photolysis as a Source of Hydroxyl Radicals (OH) in Aqueous SOA
DANA ALJAWHARY, Alex K. Y. Lee, Ran Zhao, Jonathan Abbatt, University of Toronto
Abstract Number: 230 Working Group: Aerosol Chemistry
Abstract Atmospheric particulate matter provides a medium into which gaseous organics can condense and further oxidize. While much is known about gas phase oxidation of organics in the atmosphere, there remains a large uncertainty associated with understanding the chemical processing of organics in the condensed phase. Measurements of the oxidants driving the chemical processing in the aqueous phase of organic aerosols are scarce. In addition, the sources of aqueous phase oxidants are not well characterized. Here, we propose that highly reactive OH radicals are recycled in the aqueous phase by the photolysis of organic hydroperoxides (ROOH). For this purpose, two sets of experiments were carried out: the photolysis of 1) a surrogate ROOH (t-butyl hydroperoxide) and 2) a chamber generated SOA, both in solution. The photolysis experiments were simulated under conditions mimicking those of ambient aerosols. OH radicals were measured indirectly by introducing an OH trap to the ROOH and SOA solutions. The OH probe, which is formed from the OH oxidation of the radical trap, was quantified and enabled OH production rate measurement. Photolysis products, precursor ROOH and OH probe concentrations were simultaneously detected using on-line ARI-ToF-CIMS. Intercomparison with off-line ROOH detection using the dichlorofluorescein (DCF) assay was also employed. The kinetics, products and OH yield from the photolysis experiments will be presented.