Abstract
Oil and natural gas production in the Western United States has grown rapidly in recent years, and with this industrial expansion, growing environmental concerns have arisen regarding impacts on water supplies and air quality. Recent studies have revealed highly enhanced atmospheric levels of volatile organic compounds (VOC) from primary emissions in regions of heavy oil and gas development and associated rapid photochemical production of ozone during winter. Here, we present surface and vertical profile observations of VOC from the Uintah Basin Winter Ozone Studies conducted in January – February of 2012 and 2013. These measurements identify highly elevated levels of atmospheric alkane hydrocarbons with enhancement rates of C2 – C6 non-methane hydrocarbon (NMHC) mean mole fractions during temperature inversion events in 2013at 200-300 times above the regional and seasonal background. Elevated atmospheric NMHC mole fractions coincided with build-up of ambient 1-hour ozone to levels exceeding 150 ppbv (parts per billion by volume). The total annual mass flux of C2-C7 VOC was estimated at 194 ± 56 x 106 kg yr-1, equivalent to the annual VOC emissions of a fleet of ~100 million automobiles. Total annual fugitive emission of the aromatic compounds benzene and toluene, considered air toxics, were estimated at 1.6 ± 0.4 x 106 and 2.0 ± 0.5 x 106 kg yr-1, respectively. These observations reveal a strong causal link between oil and gas emissions, accumulation of air toxics, and significant surface production in the atmospheric surface layer.