A Modeling Study to Assess the Impact of Local Point Source Emissions on Texas Regional Strategy

The Texas Clean Air Strategy (TCAS) is aimed at demonstrating attainment of the ozone standards for areas of Houston-Galveston, Beaumont-Port Arthur and Dallas-Fort Worth. This regional strategy promises to decrease ozone concentrations in other areas such as Austin, San Antonio, Corpus Christi, and Longview-Tyler-Marshall. A component of the regional strategy is based on photochemical modeling of the high ozone September 1993 episode coupled with across-the-board emission reductions of major point source and mobile source emissions. In this study we quantify the relative benefits of across-the-board reductions versus local airshed reductions on regional ozone concentrations. Specifically, we were interested in assessing the impacts of point source NOx emissions in the Corpus Christi airshed on ozone concentrations in the TCAS region. We first simulated the September 5-11, 1993 episode using the Comprehensive Air Quality Model with extensions (CAMx). Then, by conducting a set of creative emissions sensitivity simulations we have clearly demonstrated that the NOx point source emissions in Corpus Christi have negligible impact on regional ozone concentrations.