C02_02

Using radiocarbon in tree rings to track nuclear power plant emissions and fossil fuel contributions in Ontario, Canada

Martin D¹,  Pisaric M², Crann C³, Vogel F⁴

¹Department of Biological Sciences, Brock University, St. Catharines, Canada, ²Department of Geography and Tourism Studies, Brock University, St. Catharines, Canada, ³AEL-AMS Laboratory, University of Ottawa, Ottawa, Canada, ⁴Climate and Research Division, Environment and Climate Change Canada, Toronto, Canada

The atmospheric radiocarbon (¹⁴C) signature can help inform atmospheric carbon inventories for environmental monitoring and observing anthropogenic atmospheric carbon-source impacts as it is influenced by global-scale inputs (e.g., natural ¹⁴C production, the industrial revolution, nuclear weapons testing) and local inputs (e.g., nuclear power plants, urban centres). In this study, we measure Δ¹⁴C in tree rings to look at the history of anthropogenic carbon dioxide (CO₂) contributions from local emission sources in Southern Ontario that either contribute ¹⁴C (e.g., nuclear power) or ¹², ¹³C (e.g., burning of fossil fuels). Ontario’s energy portfolio includes 50% nuclear power produced using Canadian Deuterium (CANDU) reactors and includes the world’s largest nuclear power station: Bruce Nuclear Generating Station (BNGS). Results from tree ring Δ¹⁴C near Bruce show an enrichment in ¹⁴C compared to background and a correlation with emissions data from Bruce Nuclear. Since the BNGS is 200 km upwind of the Greater Toronto Area (population > 6.3 million), it is important to consider the magnitude of the ¹⁴C signature across space and time when studying the Δ¹⁴C signature in the urban area of the Greater Toronto Area (GTA).  Depleted Δ¹⁴C signatures (relative to clean air measurements at Jungfraujoch, CH, and Egbert, ON) in tree ring and atmospheric Δ¹⁴C measurements in the GTA largely reflect urban sprawl over the past 30 years, but also tell the story of COVID-19 lockdowns in March 2020 when there was less population mobility and subsequent declines in ¹⁴C-depleted atmospheric CO₂ concentrations due to less fossil fuel consumption.