Perfluoroalkyl Substances (PFASs) in the Canadian Freshwater Environment.
Bibliographic record
Abstract
Per- and polyfluoroalkyl substances (PFASs) are anthropogenic substances that are very stable in the receiving environment. Legacy perfluoroalkane sulfonates (PFSAs) and perfluoroalkyl carboxylic acids (PFCAs) are especially persistent and resistant to typical environmental degradation processes and therefore are distributed across all trophic levels and environmental compartments (soil, air, water). Since most uses of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and LC-long-chain PFCAs are banned in Canada, alternative PFASs have been in use for a number of years. Twenty-nine sites across Canada were sampled for PFASs to determine concentrations and trends. Overall, 13 PFASs were measured in 566 Canadian freshwater samples from 2013 to 2020 with a range from below the detection limit (LOD range: 0.4-1.6 ng/L) of the laboratory to a maximum of 138 ng/L (for PFBS). While PFOS and PFOA concentrations are declining significantly over time, other compounds such as PFPeA and PFBA have increased significantly over 2013-2020. Overall, the range of concentrations found in this study was similar to that of other Canadian and international studies. However, this study also found a higher frequency of detections of the replacement PFASs than that of the other, older, Canadian studies.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.005 |
| Science and technology studies | 0.004 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".