10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Organic Aerosol Evolution from Wood Combustion Chamber during the Dilution Process
QIJING BIAN, Ezra Levin, Taehyoung Lee, Jeffrey R. Pierce, Sonia Kreidenweis, Colorado State University
Abstract Number: 531 Working Group: Aerosol Physics
Abstract Previous laboratory and field measurements have documented an increasing oxygenated fraction of organics during aerosol aging and atmospheric oxidation of compounds released in biomass burning plumes. In the laboratory burn experiments carried out as part of the FLAME III study, we diluted smoke stepwise under conditions of minimal oxidation, and observed an increase in the fractional contributions of less oxygenated compounds (CxHyO) and a decrease in the fraction of more oxygenated compounds (CxHyOz), leading to a slight increase in the O:C ratio in the aerosols as the smoke was diluted. The volatility distributions for CxHy, CxHyO and CxHyOz were derived from the dilution data, and showed CxHyOz released during biomass burning has similar volatility distribution with CxHy but higher volatility than CxHyO. In addition, we also found that f60 (the fractional contributions of mass fragments with m/z 60, C2H4O2+, one of the species in CxHyOz family and a marker for biomass burning) decreased, and f44 (the fractional contributions of mass fragments with m/z 44, attributed by both CO2+ and C2H4O+, and usually a marker of oxidized species) increased, with dilution in some burns. Our studies suggest that apparent trends in f44, aerosol oxidation state and O:C ratio observed in field measurements may not be due solely to oxidation processes, but may also have contributions from physical dilution processes occurring in biomass burning plumes.