Atmospheric Scientists Conduct Ozone Measurements in Sublette County
November 21, 2011 — Courtesy of Atmospheric Science
Last winter Dr. Robert Field and his colleagues Jeff Soltis and Professor Derek Montague from the Department of Atmospheric Science carried out the first year-long phase of a two year project to understand how elevated levels of volatile organic compounds (VOC) affect the formation of wintertime ozone, a pollutant controlled through the Clean Air Act, in Sublette County, Wyoming. For the first time, a thorough assessment of the atmospheric concentrations of VOC associated with oil and gas development emissions were made in the area. The more than two thousand hourly measurements show that natural gas development is indeed the main contributor to the VOC composition of the air.
Ozone formation in winter was, until recently, an unrecognized phenomenon in the air quality community. Its discovery in Sublette County therefore drew significant attention to the region. The winter of 2011 created 'perfect storm' conditions for ozone production, with cold temperatures and deep snow cover across the Upper Green River basin. The photo above shows snow cover in mid February. The figure (right) shows ozone levels measured at the UW mobile lab, situated near the town of Boulder, south of Pinedale. Ozone levels peaked during February and March, the time period now known as "winter ozone season".
Researchers at UW and regulators at the Wyoming Department of Environmental Quality measured ozone levels at numerous monitoring stations in the basin in 2011, and postulate that stagnant air masses, enriched with ozone through the sunlight driven reactions of VOC with oxides of nitrogen, drift from south to north across the basin in late afternoon. For the first time, high ozone levels were recorded in the town of Pinedale. An initial analysis of the data shows that ozone concentrations in the basin matched those of the previous worst season, in 2008. At the UW site the National Ambient Air Quality Standard for ozone of 75 ppbv was exceeded on 11 different days. Given these high ozone levels, the UW VOC measurements are especially valuable for on-going scientific assessments attempting to model ozone formation.