Principal component analysis based source apportionment modeling of measured volatile organic compounds in a coastal urban airshed of South Texas

Corpus Christi, a near non-attainment area for ozone, is located in the semi-arid region of South Texas, and is home to several large petroleum refineries, industrial plants and a major port. The urban airshed is currently in compliance with the National Ambient Air Quality Standard (NAAQS) for ozone. Oxides of nitrogen (NOx) and volatile organic compounds (VOC) are the primary precursors for ozone. However there is limited data on these for this region. In 2005, ORSAT and the University of Texas at Austin's Center for Energy and Environmental Resources (CEER) started continuous measurement of speciated VOCs at Continuous Ambient Monitoring Stations (CAMS) 633 and 634 using automated gas chromatographs. These sites are located close to the Corpus Christi ship channel, local refineries and the industrial cluster. Hourly averages for 46 VOC species from March 2005 to December 2006 were used in this study. Principal component analysis (PCA) was employed to determine the impact of major emission sources. The PCA results at two CAMS sites were able to resolve approximately 70 and 75 percent of the variance at each site. The major VOC emissions sources impacting the coastal urban airshed of Corpus Christi were related to the petrochemical refining and petrochemical production sources, vehicle exhaust, industrial process and natural gas sources.