AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Evaluation of Anthropogenic Secondary Organic Aerosol Tracers
IBRAHIM AL-NAIEMA, Elizabeth Stone, University of Iowa
Abstract Number: 133 Working Group: Aerosol Chemistry
Abstract Secondary organic aerosols (SOA) represent an important, but undefined fraction of atmospheric fine particulate matter (PM$_(2.5)). An organic tracer-based approach has been useful in the source apportionment of PM$_(2.5) to primary and secondary biogenic sources; however, this approach has lagged behind for anthropogenic SOA. The aim of this study is to evaluate the efficacy of several classes of organic species that were previously identified in smog chamber studies of benzene, toluene, ethylbenzene, and xylenes (BTEX) in their ability to serve as tracers of anthropogenic SOA. Specifically, nitromonoaromatics, furandiones, aromatic dicarboxylic acids isomers, and 2,3-dihydroxy-4-oxopentanoic acid (a unique tracer from toluene photooxidation) were assessed in terms of their source specificity, ambient concentration, and gas-particle partitioning. First, an integrated solvent extraction and GCMS method to accurately quantify the target compounds in particle and gas phases. Second, ambient concentrations and gas-particle distributions of these species were quantified for samples were collected daily in Iowa City, IA in the fall of 2015. Third, correlations of target species with established tracers for biomass burning, vehicular emissions, and SOA were evaluated. 2,3-Dihydroxy-4-oxopentanoic acid was the most specific to toluene SOA and was only detected in the particle phase, while at low, but measureable ambient concentrations (0.3 ± 0.1 ng m$^(-3)). Aromatic dicarboxylic acids were detected at higher concentrations (e.g. 13.0 ± 4.3 ng m$^(-3) for phthalic acid), although some isomers showed appreciable partitioning to the gas phase and associations with primary sources. Nitromonoaromatics were dominated by particle-phase nitrocatechols that were associated with biomass burning. Meanwhile, other nitromonoaromatics were detected in lower concentrations and are possibly specific to anthropogenic SOA. The outcome of this study is that 2,3-dihydroxy-4-oxopentanoic and select isomers of aromatic dicarboxylic acids, nitromonoaromatics, and furandiones are good candidates for tracing anthropogenic SOA.