Abstract View
Acid-Catalyzed Aging of Secondary Organic Aerosols
CYNTHIA WONG, Sergey Nizkorodov, University of California, Irvine
Abstract Number: 267
Working Group: Aerosol Chemistry
Abstract
Secondary organic aerosols (SOA), formed through the gas-phase oxidation of volatile organic compounds (VOCs), can reside in the atmosphere anywhere between days to weeks. The formation of SOA takes place rapidly within hours after VOCs emissions, but they can undergo much slower physical and chemical processes throughout its lifetime in the atmosphere. The acidity of atmospheric aerosols spans a wide range, with the most acidic particles having negative pH values. The impact of highly acidic conditions on aerosol chemical composition remains uncertain. The goal of this work is to elucidate mechanisms and rates of acid-catalyzed aging of mixtures of reprehensive SOA compounds. SOA samples were generated in a continuous flow reactor and then collected using a foil substrate. Samples were extracted and aged by exposure to varying concentrations of aqueous sulfuric acid for 1-2 days. Analysis of fresh and aged samples was conducted using an ultra-liquid chromatography coupled with a photodiode array spectrophotometer and a higher resolution mass spectrometer to examine the chemical composition of SOA before and after aging. At the time of writing this abstract, we observe that SOA aged in moderately acidic conditions (pH 1) lead to small changes in the composition, while SOA aged in a highly acidic environment (pH -1) resulted in significant changes in the chemical composition. The prevailing mechanism of aging appears to be dehydration and condensation resulting in light-absorbing unsaturated products. The findings from this study will improve our understanding of SOA aging processes.