Multi-year trends in the spatiotemporal occurrence and fate of naphthenic acid fraction compounds in a pilot-scale engineered treatment wetland
Bibliographic record
Abstract
In the Athabasca Oil Sands region (AOSR) of Alberta, Canada, there are ~1.4 billion m 3 of fluid tailings containing known toxic constituents which will require treatment and must be reclaimed before closure. One class of contaminants of concern are naphthenic acid fraction compounds (NAFCs). While various treatment strategies have been considered, constructed wetland treatment systems (CWTSs) have emerged as a semi-passive, high throughput, and potentially cost-effective option. Here, non-targeted Orbitrap high-resolution mass spectrometry was applied to assess the NAFC remediation efficacy of a 1-ha CWTS operated over two field seasons (2021 and 2022) at a site situated in the Northern of Alberta. Concentrations of total NAFCs decreased consistently during a closed CWTS operation with OSPW recirculation at each field seasons. Concurrently, O 2 -NAFCs (i.e., classical NAs) steadily decreased while more-oxygen-rich formulae increased in spectral abundance, consistent with oxidative degradation. Attenuation rates of NAFCs were more rapid at the outset of the season (~0.53 mg/L/d), where treatment rates eventually decreased (~0.25 mg/L/d). Molecular-level characterization of treatment outcomes showed that the highest molecular weight O 2 -NAFCs detected (i.e., #C > 14) decreased the most, whereas all O 3 - and O 4 -NAFCs generally increased in relative spectral abundance. Shallow, heavily vegetated cells of the wetlands tended to have lower NAFC concentrations and more oxygen-rich compounds, suggesting substantial attenuation of NAFCs in these segments. These results demonstrate that this field-scale CWTS effectively in depletes and transforms OSPW-derived NAFCs under environmental conditions found in the AOSR
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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".