- December 09, 2025
- By Emily C. Nunez
In 2023, Canada’s worst wildfire season on record produced so much smoke that a thick haze enveloped much of the U.S. East Coast and triggered hazardous air quality alerts in the Washington, D.C. region.
University of Maryland researchers directly analyzed the wildfires’ plume—a type of pollutant that plagues the U.S. West Coast far more frequently than the East Coast. Their findings, published Nov. 25 in the journal Environmental Science: Atmospheres, revealed that chemical compounds from Canada’s wildfires remained in the atmosphere in College Park, Md., months after the smoke subsided, raising concerns about the potential health and environmental effects.
The findings could one day help improve predictive models used to study wildfires and their effects. Most chemical composition studies of long-range smoke plumes rely on federal agency satellites and planes that fly through wildfires to collect samples. On-the-ground testing is rarer, making UMD’s study unique.
The study’s senior author was chemical and biomolecular engineering Professor Akua Asa-Awuku; the lead author was chemistry doctoral student Esther Olonimoyo. Co-authors also included Yue Li, director of UMD’s Mass Spectrometry Facility, doctoral student Martin Changman Ahn and Dewansh Rastogi Ph.D. ’23.
When Canadian wildfire smoke first arrived on campus, the team collaborated with Department of Atmospheric and Oceanic Science researchers to collect air samples from the rooftop of the university’s Atlantic Building in June 2023, August 2023 and February 2024.
The researchers took those samples back to Asa-Awuku’s Environmental Aerosol Research Laboratory for chemical analysis using a high-pressure liquid chromatography method developed by Olonimoyo and another study co-author, environmental science and technology Assistant Professor Candice Duncan. While smoke plumes peaked on campus in June 2023 and visibly dissipated by August, the researchers discovered that the air samples collected in August still contained the chemical traces of wildfire smoke.
The researchers identified different classes of carbonaceous chemicals in the air, including some that could be toxic to humans in high concentrations.
It wasn’t until February 2024 that researchers saw a significant decrease in wildfire-associated compounds. “A lot of the compounds that we analyzed don’t dissipate like a primary emission, which is emitted directly into the atmosphere,” Asa-Awuku explained. “They are persistent over time and space, which suggests that they are part of an atmospheric soup that’s generating more and more of these organic compounds with time.”