Investigating the 2023 Canadian Wildfire Impacts on Air Quality in the Northeastern United States

The 2023 Canadian wildfire season heavily impacted air quality in the northeastern United States, which infrequently experiences severe wildfire smoke impacts. By the end of the season, the Canadian Interagency Forest Fire Centre estimated that approximately 42 million acres of land were burned across Canada, which is substantially higher than the average 6.18 million acres burned annually. In particular, Quebec, Alberta, and British Columbia experienced extensive wildfire activity, which triggered extreme smoke-impact events across the Northeast. The IMPROVE (Interagency Monitoring of Protected Visual Environments) ground-based network that monitors air quality in rural and remote areas across the United States recorded these smoke impacts by 24-hour PM2.5 (mass of particles with diameters less than 2.5 µm) speciated aerosol measurements taken every 3 days. This data aids in understanding the influence of particulate matter (PM) on human health as well as the intensity of visibility impairment across the region. This study investigated the origin, transport, and air quality impacts of Canadian wildfire smoke during June and July of 2023. This was done to understand the atmospheric conditions governing long-range smoke transport over North America as well as wildfire smoke’s contribution to visibility impairment in the Northeast. Additionally, this study investigates the deviations in 2023 aerosol concentrations from the 11-year average (2012-2023) quantities- due to wildfire impacts. June and July 2023 experienced rare smoke impacts in the Northeast. Organic aerosol mass (OM) accounted for 70-80% of reconstructed PM2.5 during high-impact smoke events, which is significantly higher than the 50-60% of OM typically observed in the Northeast during these months. Visibility conditions were also significantly impaired as light extinction values were estimated to be around 70-80 Mm-1, compared to typical 30-40 Mm-1 observed in the Northeast during June and July. Further research is necessary to investigate unusual deviations in other inorganic aerosol species during smoke events, such as elevated ammonium nitrate concentrations in June of 2023.