Source Apportionment And Emission Rates Of Volatile Organic Compounds In The Bakken Shale Oil And Natural Gas Region

Unconventional oil and gas (UONG) production using horizontal drilling and hydraulic fracturing has increased exponentially over the past decade in the Bakken Shale region located in eastern Montana and western North Dakota. Regional air quality is jeopardized during the development of this resource due to the volatile organic compounds (VOCs) that are emitted during drilling stages. In this study, the National Park Service measured VOC mixing ratios during an intensive field campaign in the winter of 2013-2014 to help better understand the potential impacts of these emissions on federal lands. Emission ratios with the tracer compounds, ethyne and propane, derived from a binary mixing model implicate regional oil and natural gas (ONG) production as the source of elevated alkanes in the Bakken Shale when compared to combustion emissions and background mixing ratios. Emission fluxes of alkanes calculated using a mass balance approach were similar to those from other ONG production regions, while annual emission rates for the 28,000 km region were an order of magnitude higher than rates from smaller regions. Hydroxyl radical reactivity was estimated in order to predict future regional ozone production and showed that 20-40% of total hydroxyl radical reactivity was attributable to ONG emissions.