AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Effects of Common Inorganic Salts on Aqueous Photochemistry of Secondary Organic Aerosol
ALEXANDRA KLODT, Dian Romonosky, Peng Lin, Julia Laskin, Alexander Laskin, Sergey Nizkorodov, University of California, Irvine
Abstract Number: 80 Working Group: Aerosol Chemistry
Abstract The mechanisms by which atmospheric salts change the aging of secondary organic aerosols (SOA) in cloud and fog waters are poorly understood. To address this, products of SOA aging were measured in aqueous solutions with cloud or fog water relevant concentrations of some common atmospheric salts or oxidants. The SOA was produced from a common monoterpene (alpha-pinene) and a common sesquiterpene (alpha-humulene) through ozonolysis in a flowtube. After the SOA was collected on filters, the water-soluble portion of the SOA was extracted from the filter into pure water or aqueous solutions containing dilute concentrations of H2O2, NaNO3, or NH4NO3. Aqueous samples were exposed to light in the actinic region for four hours (approximately equivalent to 64 hours in the atmosphere) or kept in the dark for four hours to simulate daytime or nighttime processing. Compositional changes were monitored by high-resolution electrospray ionization mass spectrometry at one-hour intervals, and the resultant spectra showed that the presence of salts preferentially removed higher molecular weight compounds with or without photolysis. This increased the volatility of the SOA as efficiently as or more efficiently than photolysis in pure water. This result could impact our understanding of SOA lifetimes and aging in dilute atmospheric waters such as cloud and fog waters.