AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Dynamics of Aromatic-Derived SOA in the South Coast Air Basin of California
MATT DAWSON, Jialu Xu, Robert Griffin, Donald Dabdub, University of California, Irvine
Abstract Number: 60 Working Group: Remote and Regional Atmospheric Aerosols
Abstract This research aims to incorporate an updated mechanism for secondary organic aerosol (SOA) formation from toluene and m-xylene oxidation into a state of the art regional air quality model, the University of California, Irvine - California Institute of Technology (UCI-CIT) Airshed model. The model domain covers the South Coast Air Basin (SoCAB) of California, a region containing high NOx urban areas, as well as relatively low NOx areas. Thus, the impact of this new aromatic oxidation chemical mechanism, which was developed for use over a range of NOx conditions, can be evaluated. Initially, the new SOA forming chemistry is limited to toluene and m-xylene, then extrapolated to other aromatic compounds to evaluate their potential contributions to SOA in the SoCAB region. Additionally, the effects of changing emissions scenarios on aromatic-derived SOA is evaluated by using both current and projected future emissions inventories compiled as part of the 2012 Air Quality Management Plan by the South Coast Air Quality Management District.
Finally, the propensity for SOA species formed as part of this new aromatic oxidation mechanism to partition to both the aqueous and organic phase is explored by updating the equilibrium partitioning based SOA mechanism with newly calculated vapor pressures, UNIFAC parameters, and Henry's Law coefficients for the new SOA species. As part of this work, the entire SOA module of the UCI-CIT model has been updated to use recalculated vapor pressures for SOA species using the SIMPOL.1 method of Pankow & Asher (ACP, 2008), as well as an updated SOA ‘lumping’ scheme, which groups SOA species based on similar physical properties. Details of this work will be described, and implications for this new aromatic oxidation chemistry related to air quality in the SoCAB region under varying NOx conditions and emissions scenarios will be discussed.