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Modeling

In the past, our group’s modeling efforts were driven towards development and application of new gas-phase chemical mechanisms and partitioning modules for use in the three-dimensional simulation of atmospheric secondary organic aerosol (SOA) formation (Griffin et al., 2002ab; Griffin et al., 2003; Griffin et al., 2005; Chen et al. 2006).  Our focus with regard to model development has shifted to the use of zero-dimensional models to simulate experimental reaction systems in which SOA is studied (Cai et al., 2008; Jordan et al., 2008).  More recent efforts have been directed toward simulation of isoprene chemistry and the effect of nitrogen oxides on SOA formation in aromatic systems (Xu et al., 2014).  Our efforts in three-dimensional air quality models now focus on application of our modules to investigate relevant process questions, such as the importance of particle-phase water in the formation of SOA (Chen et al., 2007; Chang et al., 2010) or how particle surfaces affect other atmospheric processes such as the oxidation of gaseous elemental mercury (Rutter et al., 2012).  A new type of modeling effort uses established software packages for chemical process simulation to investigate environmental issues such as the use of municipal solid waste as a feedstock for power generation (McPhail et al., 2014).  These efforts have been funded by the National Science Foundation, the National Oceanic and Atmospheric Administration, the Texas Commission on Environmental Quality, the Coordinating Research Council, the Environmental Protection Agency, the Shell Center for Sustainability, and the Electric Power Research Institute.

Recent findings show that ignorance of the partitioning of semi-volatile organic species to an aqueous phase likely leads to an underestimate of predicted SOA concentrations, especially in “fresh, upwind” locations (Chang et al., 2010).  In addition, our work has indicated that a simple parameterization of the oxidation of methacrolein (a first-generation oxidation product of isoprene) accurately simulates the formation of SOA in chamber experiments focused on isoprene.