Source Apportionment Using Positive Matrix Factorization of Volatile Organic Compounds at a Heavily Industrialized Monitoring Site in Houston, Texas

摘要

Positive Matrix Factorization (PMF) was applied to speciated volatile organic compound (VOC) data collected by automated gas chromatographs (auto-GCs) as part of the Photochemical Assessment Monitoring Stations (PAMS) program from 1998 to 2001 at the Clinton Drive site in Houston, Texas. The Clinton Drive site is located in the heavily industrialized Houston Ship Channel (HSC) area, where numerous large emission sources are located. This site is near major freeways and the downtown area, and therefore is also impacted by mobile sources. These various emission sources complicate source apportionment of the VOC data collected at Clinton Drive because individual sources, especially industrial sources, may be responsible for more than 90% of the VOC mass in a given sample due to industrial upsets. Fifteen factors were found using over 21,000 data points from 1998 to 2001. Factors were identified using temporal and wind-direction analysis and were consistent with known sources. Mobile source factors showed a decrease on weekends, while industrial source factors, such as petrochemical production and solvent usage, showed no day-of-week difference. Factors showed a significant dependence on wind direction, consistent with the proximity and strength of source regions. Overall, this approach using PMF gave insight into the sources impacting VOC composition and ozone formation, and can be used in evaluation of emission inventories and to better understand ozone exceedances in the Houston area.