AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Secondary Organic Aerosol from Chlorine-Radical Initiated Oxidation of Volatile Organic Compounds: Organic Aerosol Mass Yields, Composition, and Gas-Phase Products
Dongyu Wang, Surya Dhulipala, LEA HILDEBRANDT RUIZ, University of Texas at Austin
Abstract Number: 272 Working Group: Aerosol Chemistry
Abstract Ambient measurements have detected atmospheric reactive chlorine concentrations much higher than predicted by state-of-the-art air quality models, suggesting that chlorine radicals, which form from photolysis of reactive chlorine species, are more important to atmospheric chemistry than previously assumed. Chlorine radicals can initiate the oxidation of volatile organic compounds (VOCs), leading to the formation of secondary organic aerosol (SOA). Formation of SOA from chlorine-radical initiated oxidation of VOCs is currently not included in air quality models and could present a missing source of SOA.
Laboratory chamber experiments were conducted on the formation of SOA from chlorine-radical initiated oxidation of VOCs. A High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS) was used to quantify the VOCs and detect oxidation products. An Aerosol Chemical Speciation Monitor (ACSM) was used in conjunction with a Scanning Electrical Mobility System (SEMS) to quantify organic aerosol concentrations. Major gas-phase products identified in the isoprene system included methyl vinyl ketone, chloro methyl vinyl ketone, methacrolin, 1-chloro-3-methyl-3-butene-2-one (CMBO), 2-methylene-3-butenal, and 3-methylfuran; products detected in the toluene system included benzaldehyde and benzyl alcohol in addition to ring opened di-carbonyls. Toluene SOA formed in these experiments was much more oxidized than toluene SOA formed in previous studies using hydroxyl radical (OH) as oxidant. Aerosol mass yields from the oxidation of isoprene and toluene were comparable to yields from OH - initiated oxidation of these VOCs, suggesting that chlorine-radical initiated oxidation can significantly alter atmospheric chemistry and should be considered in air-quality modeling efforts.