Impact of oil and gas emissions on summertime air quality in the Northern Great Plains: WRF-Chem modeling analysis

Abstract

Oil and gas production increased dramatically last decade in the Bakken region, with accompanying changes to pollutant emissions and atmospheric concentrations. WRF-Chem model simulations of the Northern Great Plains were conducted comparing two emission scenarios using 2011 emissions to represent a baseline case with relatively low oil production (<0.4 million barrels per day) and 2014 emissions to represent a high production case (> 1.0 million barrels per day). Assessment of model predictions from the baseline scenario against ground level meteorology and air quality measurements showed good overall agreement, demonstrating suitable model performance for assessing the effect of emissions changes on pollutant levels. In the high production scenario emissions of SO₂ and NO_x were lower across most of the domain (-80% and -37%, respectively), but were significantly higher in the Bakken region (+62% for SO₂ and +110% for NO_x), and changes in VOC emissions were also relatively higher in the Bakken. Simulated pollutant concentrations followed these emission changes, with average NO_x levels decreasing for the high production scenario by 22% in the overall domain, but increasing by 72% in the Bakken. Predicted average O₃ levels increased slightly by 0.2% across the domain as NO_x levels decreased, characteristic of VOC-limited conditions, with larger increases in urban areas where NO_x reductions were greater. For the Bakken, simulations predict localized O₃ decreases in the center of the region, but increases in downwind areas. Changes between the baseline and high production scenarios demonstrate the influence of oil and gas production associated emissions on pollutant concentrations.