Integration of the SAPRC Chemical Mechanism in the SMOKE Emissions Processor for the CMAQ/Models- 3 Airshed Model

Air quality simulation models are essential tools for assessing effects of emission controls on formation of secondary pollutants such as ozone. Volatile organic compounds (VOCs) can differ significantly in their effects on ozone formation, and control strategies aimed at reducing the ozone formation potentials (“reactivities”) of the emitted VOCs are being considered in addition to mass-based controls. The Statewide Air Pollution Research Center (SAPRC) chemical mechanism, which is well suited for VOC reactivity assessment, has been implemented in EPA’s Community Multiscale Air Quality (CMAQ) model, but additional work is needed to allow SAPRC to be used in CMAQ for assessment of reactivity controls. Two major challenges must be addressed before CMAQ and SAPRC can be used effectively for reactivity assessment. First, the design of current emissions speciation databases is insufficient and needs to be corrected, because the databases do not clearly distinguish among actual chemical species, complex or poorly characterized mixtures, and model species used by specific mechanisms. Second, the emission inventory data processing to support SAPRC needs to be created. Both of these challenges are addressed by this study. Our approach will result in integration of the improved speciation database and the SAPRC chemical mechanism with the Sparse Matrix Operator Kernel Emissions (SMOKE) modeling system for CMAQ. Through this project, this SMOKE/SAPRC system will be tested to ensure support of reactivity controls and the ability to create correct emissions used in the CMAQ model. Additionally, CMAQ will be run and analyzed with and without reactivity controls to provide results for submission of an article to a peer-reviewed journal