Ten Thousand Years of Bitumen and Polycyclic Aromatic Compound Transport in the Athabasca River, Canada
Bibliographic record
Abstract
Polycyclic aromatic compounds (PACs) are a key contaminant of concern within the oil sands region of Alberta, Canada. Inputs of PACs to the Athabasca River have the potential to negatively affect aquatic ecosystems, including the downstream Peace-Athabasca Delta; however, quantitative identification of both natural and anthropogenic PAC inputs to the Athabasca River remains elusive. Here, we quantify the concentration and composition of PACs in Big Bend, a ∼4 km long and 18 m high cutbank rich in reworked bitumen-cemented unconsolidated sediments. Big Bend sediment ΣPAC concentrations exceeded 188,000 ng/g and were dominated by alkylated species, yielding a PAC compositional profile that differs subtly from McMurray Formation bitumen. A comparison of the PAC composition of Big Bend with other source materials and with 961 measures of Athabasca River water reveals an increase both in PAC concentration and in the relative input of petrogenic PACs from upstream to downstream of the bitumen-bearing McMurray Formation and the oil sands mines. Added to mining inputs is the cutbank erosion of Big Bend, which supplies on average ∼410 kt of sediment and ∼5.3 tons of PACs annually to the Athabasca River immediately upstream of the Peace-Athabasca Delta. These inputs supply about 10% of the river sediment load and as much as half of the PACs transported by the Athabasca River.
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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".