Extended Abstract (44K)15.2
Evaluation of the impacts of emission sources in Corpus Christi on the regional air quality
Sunil Kumar, Texas A&M University, Kingsville, TX; and K. John
A photochemical modeling study was undertaken to evaluate the impacts of Corpus Christi emission sources on the nearby areas of San Antonio and Austin. CAMx, a photochemical model, developed by ENVIRON was used for this purpose. The high ozone episode of July 7-12, 1995 was simulated using the CAMx. This episode was used by the Alamo Area Council of Governments (AACOG) for developing its Ozone Flex Plan for submitting it to the United States Environment Protection Agency (US EPA). This episode was selected to be a good episode for evaluating ozone and precursor transport from the Corpus Christi area. Meteorological fields needed to drive the CAMx model for this period were produced by the Regional Scale Atmospheric Modeling System (RAMS, version 3a) and acquired along with other required data such as, emissions, land use/land cover, chemical mechanism parameters, photolysis rates, vertical diffusivity, initial, top, and boundary conditions from the AACOG. The base case run was evaluated for its ability to capture both the 1-hour and 8-hour ozone levels in San Antonio, Austin, and Corpus Christi using the US EPA approved statistical evaluation parameters namely, unpaired peak accuracy, averaged peak accuracy, peak timing bias, overall bias, and overall gross error. Time-series analyses were also undertaken for graphical comparison of the observed and modeled ozone concentrations. After finding the model performance to be satisfactory, it was then used for two emissions control scenarios to judge the effects of anthropogenic emissions in Corpus Christi on the regional air quality, especially the metropolitan areas of San Antonio and Austin. In the first case, all major point source emissions were taken out from Corpus Christi, while the second scenario involved zeroing out of all emissions from there. Results from the first control case indicate that the major point sources contribute usually 3 to 4 ppb during the nighttime hours between 10 PM and midnight towards the 1-hour ozone vels in San Antonio and about 1 ppb in Austin. Maximum 8-hour contributions were less than 1 ppb at both the sites. All sources together from Corpus Christi contribute usually 10 to 20 ppb towards the 1-hour ozone levels in San Antonio and upto 1 to 3 ppb in Austin for this episode. The maximum contributions to the 8-hour averaged ozone levels were approximately 8 to 9 ppb and 1 ppb in San Antonio and Austin, respectively. The benefits of the emission reduction in Corpus Christi were observed immediately downwind of the major source region during the daytime hours. However, reduction in emissions from Corpus Christi showed an increase in the local ozone levels during the late evening and early morning hours.
Session 15, Urban airshed modeling
Friday, 24 May 2002, 10:45 AM-11:30 AM
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