AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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SOA Formation from Tailpipe Emissions from On-road Gasoline Vehicles
YUNLIANG ZHAO, Rawad Saleh, Georges Saliba, Greg Drozd, Hector Maldonado, Satya Sardar, Bruce Frodin, Allen H. Goldstein, Allen Robinson, Carnegie Mellon University
Abstract Number: 411 Working Group: Urban Aerosols
Abstract On-road gasoline vehicles have been indicated as a major source of SOA in urban areas, but our understanding of SOA formation from tailpipe emissions is poorly constrained. Results from recent chamber experiments with dilute tailpipe emissions from gasoline vehicles have shown that only a small fraction of measured SOA can be explained by light aromatic compounds (C6-C9). Understanding what cause(s) the large discrepancies between measured and predicted SOA from tailpipe emissions is critical to determining the contribution of gasoline vehicles to atmospheric PM, improving the performance of atmospheric models, and making effective emission control polices. To determine the cause(s), we have performed a comprehensive study to characterize primary emissions and investigate SOA formation from tailpipe emissions from on-road, in-use light-duty gasoline vehicles. We have comprehensively characterized primary emitted hydrocarbons, corresponding to the saturation concentration range of C2-C36 n-alkanes. These quantified hydrocarbons include three important classes of SOA precursors, single-ring aromatic compounds, intermediate-volatility organic compounds and semi-volatile organic compounds. SOA formation from dilute exhaust was measured through smog chamber experiments. The mass balance between measured and predicted SOA is achieved by including light single-ring aromatic compounds, intermediate volatility organic compounds and semi-volatile organic compounds and accounting for the effects of NOx levels on SOA formation. This mass balance indicates that light single-ring aromatic compounds, intermediate volatility organic compounds and semi-volatile organic compounds all are important precursor classes. The contribution of light-duty gasoline vehicles to SOA production from on-road vehicles is updated based on these new findings.