AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Following Carboxylic Acid and Peroxyacid Chemistry in the Formation of Aqueous Secondary Organic Aerosol Produced from Oxidation of Monoterpenes
MICHAEL LINK, Delphine Farmer, Colorado State University
Abstract Number: 745 Working Group: There Must be Something in the Water: Cloud, Fog and Aerosol Aqueous Chemistry for Aerosol Production
Abstract Anthropogenic emissions facilitate the formation of aerosol liquid water which perturbs the oxidation chemistry of the atmosphere including the oxidation of biogenic volatile organic compounds. Monoterpenes undergo oxidation in the atmosphere to form small oxygenated water-soluble organic compounds that can further undergo oxidation in the aqueous phase and serve as precursors for secondary organic aerosol (aqSOA). This oxidation pathway produces compounds that can help to explain the high oxygen to carbon ratios commonly observed in ambient aerosol. While the mechanisms of oxidation and subsequent aqSOA formation are well understood for a few compounds (i.e. methylglyoxyl, isoprene epoxydiol) the role of organic peroxides in aqueous reactivity and radical recycling are not as well constrained. We have oxidized two model monoterpenes, limonene and terpinolene, in an oxidation flow reactor under variable relative humidity conditions and hydroxyl radical exposures (OHexp) to study how these variables influence the production of water-soluble organic species in the gas-phase and how that affects aqSOA production. Under constant OHexp conditions increasing humidity in the chamber was observed to generally increase SOA mass production from monoterpene oxidation by an order of magnitude or more. Under constant relative humidity conditions, different gas-phase species were generally observed either to be produced or removed in response to changes in OHexp. Formic and performic acid were chosen as surrogate acid/peroxyacid species to follow mechanistically through the cycle of aqueous oxidation to understand how the evolution of organic acid and peroxyacid species contribute to the magnitude of SOA formation under conditions of high relative humidity.