Dendrochronology can provide a glimpse into past periods that lack long-term ecological and environmental data. With the growing concern of climate change and the need to reach net-zero carbon, contributions of nuclear energy sources to meet net-zero goals continue to be discussed. Ontario obtains a large amount of energy from Canadian Deuterium (CANDU) reactors at the Bruce, Pickering and Darlington nuclear facilities. Conveniently, tree-rings can be used to measure radiocarbon (14C) emissions released during maintenance activities. Atmospheric 14C can be measured in tree rings via accelerator mass spectrometry (AMS). These proxy-records can provide annually resolved data that integrates atmospheric carbon dioxide (CO2) via photosynthesis. 

Continuing the work of past studies, we will be measuring 14C to determine how atmospheric CO2 is being influenced by 14C emissions from nuclear sources and old carbon derived from fossil fuel combustion (12C or 13C). Tree-ring 14C data will be compared to atmospheric CO2 and 14C levels measured by Environment and Climate Change Canada (ECCC), environmental monitoring of reactors from the Canadian Nuclear Safety Commission and to data from the ECCC clean-air site location in Egbert, ON. White spruce (Picea glauca) trees were sampled near the Bruce nuclear facility and in the City of Toronto to investigate fossil fuel emission impacts from high traffic areas as well as potential effects COVID-19 may have had with the significant decrease in fossil fuel consumption after March 2020. It is hypothesized that samples from Bruce will be enriched in 14C, while samples from Toronto will be severely 14C-depleted until 2020 with evidence of decreased 12C and 13C levels.