Impact of Fugitive Emissions from the Marcellus Basin on Northeastern US Air Quality

The past decade has seen rapid rises in oil and gas production from the Marcellus region associated with hydraulic fracturing. These activities are associated with increases in fugitive emissions of methane and other higher reactive non-methane volatile organic compounds (NMVOCs), as well as reactive nitrogen species (NO_x). Here, we present an optimized gridded methane emission inventory for the Marcellus shale-gas region constrained via top-down inverse methods to surface in situ measurements across the Northeastern United States. We then estimate the emissions of fugitive NMVOCs by applying ratios of these species measured relative to methane observed from plumes sampled from aircraft. We then apply these emission estimates within the GEOS-Chem chemistry-transport model in order to quantify their impact on downwind air quality in the Northeastern United States for the year 2017. We separately isolate the impacts of methane, NMVOCs, and NO_x, and also compare to the EPA gridded emissions for this region and sector. The magnitude that fugitive emissions contribute to enhancements of criteria pollutants on non-attainment days in Northeastern metropolitan areas is explored.