Measurements of Highly Reactive Volatile Organic Compounds Using Proton-Transfer-Reaction Mass Spectrometry during the 2006 Texas Air Quality Study II Field Campaign

It has been established from the TexAQS 2000 study that both VOCs and NOx (NO and NO₂) play a key role in the ozone photochemical production process in the Houston area. In order to develop an effective control strategy to reduce ozone production, it is crucial to identify the both the spatial distribution and concentration of NOx and VOCs, particularly the highly reactive volatile organic compounds (HRVOCs) which efficiently and rapidly form ozone in an urban environment. In this presentation, ground-based HRVOCs measurements obtained using proton-transfer reaction mass spectrometry (PTR-MS) during the 2006 Texas Air Quality Study (TexAQS II) will be presented. The measurements were conducted at two sites consecutively: from 17 August to 9 September on the downtown campus of University of Houston and from 14 to 30 September at the Aldine Environmental Protection Agency site. During the campaign, we detected fourteen VOCs (individually or as groups), including methanol, propene, acetaldehyde, butenes, acetone, acetic acid, isoprene, methyl vinyl ketone + methacrolein, C4-carbonyl compounds, benzene, toluene, C2- and C3-benzenes, and monoterpenes. Strong weekend effects were observed at both sites, especially in aromatic compounds, indicating the dominant influence of vehicle emissions on the VOC concentrations. Propene and butenes were identified as the major alkene species during the observational period and exhibited influences from the Houston Ship-Channel. In addition, our results suggest that unexpected emissions from point sources may have significant impacts on the local and regional air quality.