The Houston-Galveston area has the largest network of online instrumentation for volatile organic compounds (VOCs) worldwide. These auto-gaschromatographs perform hourly samplings and include 56 VOC target compounds as requested by the US EPA. Measurements started at some sites as early as 1997. These data sets allow site specific and compound specific trend analysis of VOCs. They also allow detailed VOC source analysis.

This presentation reports dependence of speciated VOCs on ambient temperature and wind conditions based on this large unique data set in the Houston-Galveston area and discusses the impact of these meteorological parameters on evaporative emissions. These processes may be important to fuel VOC precursors in urban photochemical processes. Results of this VOC data analysis study also show that some sites may give insight into background VOC levels depending on the wind direction. These sites are located close to the Gulf of Mexico and monitor subtropical marine background conditions when southerly winds prevail. Preliminary analysis for a 2-month period in 2006 reveal the following background values for the following VOCs: ethane (0.8-1.1 ppbv), propane (370-400 pptv), i-butane (130-160 pptv), n-butane (120-160 pptv), i-pentane (140-190 pptv), n-pentane (80-110 pptv), acetylene (80-90 pptv), benzene (50-70 pptv), toluene (30-100 pptv).