Source identification and apportionment of volatile organic compounds in Houston, TX

Hourly concentrations of ambient volatile organic compounds (VOCs) were analyzed between June and October 2003 at three sites, in order to further understand emissions of VOCs in the Houston area. Ambient concentrations of 54 VOCs from three monitoring sites in the heavily industrialized Houston Ship Channel were analyzed using positive matrix factorization (PMF). Hourly concentrations were divided into weekly data sets and analyzed to determine the most important source types that contribute to the measured VOC concentrations at these three sites. For each monitoring site, three or four sources were identified for each week as major contributors to ambient VOC concentrations using PMF. The sources isolated by the model are consistent with the chemical compositions of refinery, petrochemical and evaporative emissions, which are also the dominant inventoried sources of VOCs in Houston Ship Channel region. A night-time data analysis was also performed at two sites to investigate the effect of photochemical reactions on source attribution of VOCs.