Understanding the Oxidized Nitrogen Budget via Airborne Measurements Downwind of Oil Sands Operations in Alberta, Canada

Abstract:

Oxidized nitrogen species (NOz = NOy – NOx) play an important role in temporarily or permanently sequestering NOx from the ozone producing radical cycle and thus impacting local and regional ozone levels. Alberta’s Oil Sands region contains the world’s largest deposits of commercially extractable bitumen and significant NOx is produced during its extraction. This NOx has a potentially significant impact to regional ozone, depending on the type and magnitude of NOz formation. The sources of NOx include both point and mobile sources and are part of a mix of other pollutants including SO₂, CO, PM and a wide variety of VOCs. Here, we present aircraft measurements of NOz species performed downwind of Alberta’s Oil Sands over 8 weeks in the spring and summer of 2018. Species measured include NO, NO₂, NOy, HONO, HNO₃, HNO₄, N₂O₅, organic nitrates and particle nitrate, using a variety of instruments including chemical ionization mass spectrometry (CIMS), chemiluminescence monitors and aerosol mass spectrometry (AMS). Attempts to close the NOz budget between the sum NOz (Chemiluminescence) and speciated NOz (CIMS+AMS) as well as seasonal differences in the distribution will be discussed. The results demonstrated distinct differences between the summer and winter with respect to the chemical composition of NOz, in particular for gaseous organic nitrogen species, reflecting increased photochemistry during the summer. Comparisons with an operational air quality forecast model GEM-MACH (Global Environmental Multi-scale - Modelling Air quality and CHemistry) will also be shown to investigate the models ability to capture the variation of these species.