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NARSTO Workshop on Innovative Methods for Emission Inventory Development and Evaluation University of Texas, Austin October 14-17, 2003 |
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Positive Matrix Factorization Analysis of Volatile Organic Compound Concentrations in Houston, TX
Birnur Buzcu and Matthew P. Fraser
Civil and Environmental Engineering
Rice University, Houston, TX 77005
Recent measurements during TexAQS 2000 have found that emissions of volatile organic compounds (VOCs) from petrochemical facilities are underestimated in existing emission inventories. To further investigate the sources of VOCs in Houston, receptor modeling has been performed on ambient air samples collected in Deer Park, Texas. Concentrations of 55 different VOCs measured hourly between January 29 and December 31, 2001 were obtained from data collected by the Texas Commission on Environmental Quality (TCEQ). In the current research, VOC data were divided into weekly intervals and positive matrix factorization (PMF) was applied to the hourly VOC data in each interval to determine source profiles and contributions. PMF receptor modeling isolated profiles resembling the composition of known sources, including motor vehicle exhaust, petrochemical production, petroleum refining, natural and liquefied petroleum gas, and gasoline headspace vapors. The temporal variability in source contribution during 2001 was determined as well as the overall magnitude of contribution from these sources. The calculated source contributions have been compared to existing inventories, and the relationship between source contributions and ozone concentrations and wind direction has been used to better understand the relationship between VOC emissions and ozone formation.