The development of hydraulic fracturing and horizontal drilling has enabled a rapid increase in the past several years in oil and natural gas production in the Bakken Formation region of western North Dakota and eastern Montana. While national reductions in emissions of sulfur and nitrogen oxides have yielded substantial decreases over the past decade in fine particle nitrate and sulfate concentrations across most of the U.S., a few regions of the country, including the Bakken region, instead show increases in fine particle concentrations and haze, especially in winter. In order to better characterize possible impacts of increased oil and gas production in the Bakken region on regional air quality, two field campaigns were conducted. An initial scoping study was conducted from February to April 2013. A second, more detailed study was conducted between November 2013 and March 2014. A combination of mobile and fixed air quality sampling was used in the studies. The most comprehensive measurements were made at the north unit of Theodore Roosevelt National Park. Additional measurements were made at several other federal sites in the region, including Medicine Lake and Fort Union. Gas phase measurements included ozone, volatile organic compounds (VOCs), methane, nitrogen oxides, nitric acid, suflur dioxide, and ammonia. Fine particles were speciated using an Aerosol Mass Spectrometer, online and offline ion chromatography, and an aethalometer. This presentation will review key findings from the two studies. Winter ozone concentrations in the region were consistently low. The most obvious air quality issues observed at the measurement sites were periods of elevated fine particle concentrations which result in significant haze and visibility impairment. While strong winds from the west often bring clean air to the region, periods of stagnation and air recirculation result in substantial formation and accumulation of secondary particulate matter, especially ammonium nitrate. The resulting episodes are regional in nature, stretching across the study observational network. Speciated VOC measurements will be used as source tracers to examine the influence of local oil and gas production and other source types during the hazy periods. The relative availability of ammonia and nitric acid will be examined to determine how further development might influence future levels of haze.

Characterizing air quality impacts of oil and gas development in the Bakken formation region

249th National Meeting (2015)

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