Evaluating volatility distributions of semi- and intermediate-volatility organic compounds from the Alberta Oil Sands for modeling the formation and evolution of secondary organic aerosols.

Abstract:

Organic aerosols (OA) are a major component of regional and global pollution. As an important component of particulate matter (PM), OA has a complex effect on climate and health, at all geographic scales. The Athabasca Oil Sands are a large source of secondary OA in Canada, with a production level similar to major urban areas, despite low concentrations of combustion markers.

Following recent intensive aircraft campaigns evaluating emissions and transformation of pollutants from the Oil Sands in 2013 and 2018, multiple possible sources of primary semi- and intermediate-volatility organic compounds (P-S/IVOC) have been characterized, with divergent volatility distributions. This work uses a customized box model to evaluate the published volatility distributions against field measurements with respect to the corresponding formation and evolution of OA as well as oxygen-to-carbon ratios. The box model approach includes using an ensemble of several volatility basis set (VBS) parameterizations to model secondary OA. This approach allows exploration of parameterizations for SOA precursor oxidation and yields, molecular fragmentation, and the effect of phase separation.

Additionally, this work describes a VBS approach for predicting SOA into Environment and Climate Change Canada’s 3-D air quality model, Global Environmental Multiscale – Modeling Air quality and CHemistry (GEM-MACH). High-resolution results (2.5 x 2.5 km grid) are compared to measurements taken during flights at the Oil Sands, as well as to ground-based monitoring networks across North America (10 x 10 km grid).