Hybrid dispersion and chemical transport modeling frameworks for characterizing sources of ambient hydrocarbons in the Permian Basin

Emissions from oil and gas operations contribute to elevated air pollutant concentrations in oil and gas production regions. Attribution of elevated concentrations to specific oil and gas sources is challenging because the sources are extensive and their emissions have highly complex spatial, temporal, and chemical emissions profiles. In this work, detailed emissions modeling is coupled with dispersion- and chemical transport modeling to evaluate the sources of light alkanes (ethane and propane) measured at an air quality monitor in the Permian Basin in west Texas. Local sources (< 50km away) are shown to produce the largest observed concentrations, but concentrations attributed to distant sources ( 50 km away) are, at times, dozens of ppb and contribute, on average, 20% of observed concentrations. At some times, distant sources are predicted to contribute more than 90% of the observed concentrations. Atmospheric chemistry is not predicted to significantly impact ethane and propane concentrations from local sources, but concentrations from distant sources and of higher molecular weight reactive hydrocarbons (e.g., benzene) can be decreased by up to 40% due to reactive losses, depending on the species and the season. These findings suggest modeling approaches for predicting ambient air quality in complex and extensive oil and gas regions like the Permian Basin require detailed treatment of both local and regional sources as well as atmospheric chemistry.