PNNL

Abstract

Observations of C1-C10 hydrocarbon mixing ratios measured by in-situ instrumentation at the La Porte super site during the TexAQS 2000 field experiment are reported. The La Porte data were compared to a roadway vehicle exhaust signature obtained from canister samples collected in the Houston Washburn tunnel during the same summer to better understand the impact of petrochemical emissions of hydrocarbons at the site. It is shown that the abundance of ethene, propene, 1-butene, C2-C4 alkanes, hexane, cyclohexane, methylcyclohexane, isopropylbenzene, and styrene at La Porte were systematically impacted by petrochemical industry emissions. Coherent power law relationships between frequency distribution widths of hydrocarbon mixing ratios and their local lifetimes clearly identify two major source groups, roadway vehicle emissions and industrial emissions. Distributions of most aromatics and long chain alkanes were consistent with roadway vehicle emissions as the dominant source. Airmass reactivity was generally dominated by C1-C3 aldehydes. Propene and ethene sometimes dominated air mass reactivity with HO loss frequencies often greater than 10 s-1. Ozone mixing ratios near 200 ppbv were observed on two separate occasions and these air masses appear to have been impacted by industrial emissions of alkenes from the Houston Ship Channel. The La Porte data provide evidence of the importance of industrial emissions of ethene and propene on air masses reactivity and ozone formation in Houston.