Passive Hydrocarbon Sampling in a Shale Oil and Gas Production Area Shows Spatially Heterogeneous Air Toxics Exposure Based on Type and Proximity to Emission Sources

Abstract

Shale oil and gas production areas are especially active in Texas. The Eagle Ford Shale in south central Texas contributes substantially to US oil and gas production; it has repeatedly been the focus of air quality studies due to its associated emissions. Among these emissions are hazardous air pollutants such as benzene, a known carcinogen. To monitor exposure to such compounds, we teamed up with local citizens in 2019 to begin a passive sampling study for hydrocarbons. The study tracked selected non-methane hydrocarbons at six locations throughout a busy central production area of the shale. A state air quality monitoring station allowed for a comparison exercise, and we report both the results of that exercise and the observations from various properties affected by the surrounding oil and gas exploration activities. The passive samplers accurately reflected mean to median ambient hydrocarbon levels despite high variability and skewness in the hourly measurements. Field sites either right next to oil and gas production pads, surrounded by more surface pads than other sites, or affected by an additional emission source showed higher exposure to selected hydrocarbons. Passive sampling shows promise to bridge the gap between centralized air monitoring and campaign-style mobile monitoring to evaluate hydrocarbon emissions and abundances. It is a cost-effective way to provide both spatial and temporal information on exposure levels.