10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Laboratory Investigations of SOA Photolysis
MARIA ZAWADOWICZ, John Shilling, Pacific Northwest National Lab
Abstract Number: 1065 Working Group: Aerosol Chemistry
Abstract Secondary organic aerosol (SOA) accounts for a large fraction of tropospheric particulate matter in accumulation mode. Accurate representation of SOA life cycle in models is needed to quantify its effects on radiative forcing and air quality. While SOA production rates and mechanisms have been extensively investigated, the exact loss pathways are still uncertain. Most current large-scale models account for dry and wet removal of SOA, but not for chemical losses, such as photolysis or surface oxidation by OH and ozone. Model estimates indicate that introducing an SOA photolysis rate equivalent to 0.04% of typical NO2 photolysis rate can lower tropospheric SOA mass by 40 – 60%. Laboratory measurements of SOA photolysis rates are necessary to better constrain theoretical estimates. This study reports a series of batch-mode environmental chamber experiments quantifying UV photolysis rates of atmospherically-relevant SOA types. These experiments aim at assessing the photolytic contribution to SOA removal for several precursors (including isoprene, α-pinene and toluene), high- and low-NOx pathways and different RH conditions.