AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Polar Fraction of Semi-volatile Organic Compounds in Biomass Burning Emissions and Their Chemical Transformations during Aging with Oxidation Flow Reactor
DEEP SENGUPTA, Chiranjivi Bhattarai, Vera Samburova, Adam Watts, Hans Moosmuller, Andrey Khlystov, Desert Research Institute
Abstract Number: 614 Working Group: Biomass Combustion: Emissions, Chemistry, Air Quality, Climate, and Human Health
Abstract Semi-volatile organic compounds (SVOCs) produced by biomass-burning (BB) contribute to radiative forcing of climate and could also cause adverse health effects. The polar fraction of SVOCs constitutes a significant part of BB organic aerosols and this is why it is important to characterize its chemical composition and reactivity. In the present study, selected representative fuels (both globally and regionally important) were burned under controlled conditions using the DRI chamber facility. Gas and particulate phase biomass burning emissions were aged in an oxidation flow reactor (OFR) to mimic 5-7 days of atmospheric aging. Fresh and OFR-aged biomass-burning aerosols were collected on quartz filters for thermal/optical reflectance (TOR) determination of organic carbon (OC) and on TIGF filters in tandem with XAD resin media for organic compound speciation. TIGF filters and XAD were extracted with a mixture of dichloromethane and acetone. The polar fraction was derivatized prior to GC/MS analysis. 85 polar compounds were quantified including mono and dicarboxylic acids, methoxylated phenols, aromatic acids, anhydrosugars, resin acids and sterols. Carbon content of the quantified polar compounds was found to constitute 2%-5% of the TOR OC. Levoglucosan was found in significant amounts only in Eucalyptus, a representative of flaming combustion type fuels. High abundance of methoxyphenols and resin acids are found in peat burning emissions (smoldering combustion). Concentrations of higher molecular weight compounds decreased after OFR aging, while concentrations of low molecular weight compounds increased. This indicates a significant extent of fragmentation reactions in the OFR. Methoxyphenol concentrations decreased after OFR aging while a significant increase in dicarboxylic acids especially maleic acid was observed. These results can be used to perform source apportionments and predict the processes occurring during atmospheric transport.