Distributions of air pollutants associated with oil and gas development measured in the Upper Green River Basin of Wyoming.

Abstract

Diffusive sampler monitoring techniques were employed to assess the spatial variability of air pollutants associated with the Pinedale Anticline and Jonah Field oil and natural gas (O&NG) developments in the Upper Green River Basin, Wyoming. Diffusive sampling identified both the extent of wintertime ozone episodes and the distributions of oxides of nitrogen (NOx), volatile organic compounds (VOC) including BTEX (benzene, toluene, ethylbenzene and xylene isomers), and volatile polycyclic aromatic hydrocarbons (PAH), allowing the influence of different O&NG emission sources to be determined. Concentration isopleth mapping of both diffusive sampler and continuous ozone measurements showed the importance of localized production and advective transport. As for ozone, BTEX and NOx mixing ratios were elevated within O&NG development areas, with localized hotspots being evident. One BTEX hotspot was related to an area with intensive development activities, while a second was located around a water treatment and recycling facility. Contrastingly, NOx hotspots occurred at different locations, often being associated with vehicular emissions. Comparisons of observed selected PAH and VOC species ratios at a roadside site in the town of Pinedale with those measured in O&NG development areas show that traffic emissions contribute minimally to VOCs in these latter areas. Thus elevated levels of naphthalene, often observed at BTEX hotspots, must arise from non-traffic emission sources. Possible sources include waste gas incineration and contaminated water treatment. In addition we note that contour mapping of the spatial distribution of pollutant species concentrations determined by diffusive sampling has considerable potential utility for the validation of emission inventories.