Impacts of Arctic Oil Field NOx Emissions on Downwind Bromine Chemistry: Insights from 5 years of MAX-DOAS observations

Abstract

Oil and gas production is a substantial source of nitrogen oxides to the atmosphere, with significant impacts particularly in remote regions without other large local NOx sources. In the Arctic, these emissions impact regional halogen and HOx chemistry, altering the oxidation of atmospheric pollutants. In this work we utilize Multiple Axis Differential Optical Absorption Spectroscopy (MAX- DOAS) NO2 and BrO measurements at Utqiagvik, Alaska from 2012-2016. During the spring months when atmospheric bromine chemistry is most prevalent, we find 8% of observations are impacted by observed NO2 differential slant column densities (dSCDs) over 5e15 molecules cm−2, which we classify as polluted. Of this fraction, approximately half can be attributed to sources outside the immediate vicinity of Utqiagvik. During these polluted times, observed BrO lower tropospheric column densities (LT-VCDs) are 60% lower on average than those retrieved during non-polluted times. During times when the local wind direction corresponds with a large collection of oil and gas extraction facilities approximately 300 km southeast of Utqiagvik, observed BrO LT-VCDs were 30% lower than clean air times. These observations show that current oil and gas operations in the Arctic are impacting the natural atmospheric photochemical processes.