Tracking nuclear generating station emissions and fossil fuel contributions using tree rings in southern Ontario, Canada
Bibliographic record
Abstract
Changing atmospheric concentrations of stable (12C, 13C) and radioactive (14C) isotopes of carbon are an important indicator of the Anthropocene. Carbon from anthropogenic sources can be released to the atmosphere as radiocarbon (14C) from nuclear power and above-ground nuclear weapons testing. Carbon-12 and carbon-13 (12,13C) are derived from fossil fuel combustion in the urban, industrial, and transportation sectors. In Ontario (Canada), ~half of the province’s power generation is derived from three nuclear generating stations (NGS), including Bruce Nuclear Generating Station (BNGS), one of the world’s largest NGS. Thus, understanding the contributions of NGS emissions and fossil fuel use in urban, industrial, and transportation sectors is essential for developing accurate atmospheric carbon inventories in southern Ontario. This study analyzes tree-ring Δ14C (the amount of 14C in a particular sample) as a proxy for atmospheric Δ14C by isolating tree-ring alpha cellulose and using accelerator mass spectrometry (AMS). Results indicate that Δ14C tree-ring signatures from white spruce (Picea glauca) and blue spruce (Picea pungens) can track 14C-enrichment from NGS 14C emissions when comparing peaks in tree-ring Δ14C offset data and 14C emissions during the trees’ growing season. Tree-ring Δ14C signatures are also observed in Canada’s largest urban centre the City of Toronto, which is nearby to Pickering Nuclear Generating Station (PNGS). Conversely, Toronto also experiences fossil fuel contributions and thus is susceptible to the Suess Effect. We observe fossil fuel-derived 12,13C from urban activities via tree-ring Δ14C-depletion. Peaks were also observed in the tree-ring Δ14C offset and PNGS 14C emissions. To determine 14C-enrichment or -depletion, sites are compared to a regional clean-air site (Egbert, Ontario, Canada) and northern hemisphere atmospheric background sites (Northern Hemisphere Zone 1; Jungfraujoch, Switzerland). Tree growing season and meteorology analyses strengthen the validity of this study’s results. Similar Δ14C levels from white spruce tree rings and an Environment and Climate Change Canada (ECCC) air sampler (ρ = 0.9273) were also observed. Thus, tree-ring Δ14C signatures can be used to measure local influences from anthropogenic sources of NGS 14C emissions and fossil fuel contributions to help build an atmospheric carbon inventory.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".