Exploring Surface Water-Bitumen Interactions in Athabasca Oil Sands Wetlands Using Stable and Radiocarbon Isotopes
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide Naphthenic acid fraction compounds (NAFCs) have been identified as aquatic contaminants of concern associated with bitumen extraction in Canada’s Athabasca oil sands region. Previous investigations found that NAFCs occur and degrade in young (<100-year-old) wetlands, but the degree to which these NAFCs might be bitumen-derived remains unclear. To quantify contributions of modern versus fossil NAFCs, carbon isotope-based methods were applied to two intensively sampled wetlands suspected to be influenced by oil sands. Carbon-13 isotope ratios measured by pyrolytic decarboxylation (δ 13 C pyr ) fell within a narrow range (−27.5 to −26.0‰) and radiocarbon measurements (Δ 14 C) revealed a significant fossil carbon contribution (−795 to −290‰), presumably from bitumen. Along the flow pathway of one wetland, a positive shift of ∼1.5‰ in δ 13 C pyr correlated with increasing distance from a suspected oil sands point source. Lower Δ 14 C values (i.e., less 14 C) at this site corresponded to lighter δ 13 C pyr r values – the opposite trend found in previous applications of δ 13 C pyr analyses, whereby bitumen-derived NAFSs were around −22 to −21‰. This study shows how source attribution of NAFCs in surface water using δ 13 C pyr may be less straightforward compared to groundwater, possibly due to differences in natural attenuation processes between these two environments.
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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 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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 | 0.000 |
| 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".