AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Simulating the Combined Effect of Volatility, Multigenerational Chemistry, Unspeciated Precursors and Vapor Wall-Losses on Ambient Organic Aerosol in 3-D Air Quality Model
ALI AKHERATI, Christopher Cappa, Michael Kleeman, Shantanu Jathar, Colorado State University
Abstract Number: 367 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Combustion-related primary organic aerosol (POA) is now known to be semi-volatile and reactive. Intermediate volatility organic compounds (IVOC), multigenerational chemistry and vapor wall losses during chamber experiments have all been shown to be important for the atmospheric production of secondary organic aerosol (SOA). While some of these processes have been accounted for in 3-D chemical transport models, it is unclear how these processes interact with each other at varying spatial and temporal scales and control the size, mass, composition and source contribution of ambient organic aerosol (OA) in urban and regional airsheds. To address this uncertainty, in this work, we simulated the air quality over Southern California and the eastern United States using a state-of-the-science 3-D chemical transport model (UCD/CIT) over a summer month. The chemistry and thermodynamics of the OA was modeled using the experimentally-constrained statistical oxidation model. A suite of simulations was performed over both geographical domains that systematically identified the relative importance of each source/process of interest to the ambient burden of OA. Preliminary results for Southern California indicate that a semi-volatile treatment of POA decreases while reactive POA, IVOCs and accounting for vapor wall-losses increases OA mass concentrations; multigenerational aging was found to have very small effect. Overall, the OA mass concentrations are only marginally enhanced when considering the influence of POA and IVOCs together but dramatically enhanced when accounting for vapor wall losses. Ongoing work is focussed on a systematic comparison of predictions with measurements not only of mass concentrations, but also of size and composition. Finally, we will investigate through the use of a source-resolved model, the contributions of gasoline and diesel mobile sources to the ambient OA burden.