Characterization of Atmospheric Volatile Organic Compounds in the North Dakota Bakken Formation

Abstract:

A field campaign was conducted from 23 November 2013 through 28 March 2014 in the Bakken formation of North Dakota to investigate the impacts of rapidly increasing oil and gas production operations on air quality throughout the region. Whole air samples were collected at three different sites during the study period for volatile organic compound (VOC) measurements. The main sampling location was the north unit of Theodore Roosevelt National Park (THRO), where one daytime and one nighttime sample were collected each day throughout the campaign period. Daytime samples were also collected every second day at the Fort Union Trading Post National Historic Site (FOUS) and once a week at the Medicine Lake National Wildlife Refuge, MT. A signature of elevated nonmethane hydrocarbon (NMHC) mixing ratios was observed throughout the campaign at all three sites; THRO and FOUS had the highest levels as they are located in high well density areas. Moreover, the C₂-C₅ alkane mixing ratios were approximately an order of magnitude greater than regional background levels. Light alkane mixing ratios at THRO, the most impacted site, were similar to those at urban sites influenced by petrochemical industry emissions, with ethane and propane reaching maximums of 95 ppbv and 164 ppbv, respectively. The i-pentane to n-pentane ratio for all sites was ~0.75, clearly demonstrating the widespread impact from oil and gas production emissions throughout the region. Alkanes dominated the hydroxyl radical reactivity, and their overall influence on regional air quality will be explored.