Perfluorinated Alkyl Acid Concentrations in Canadian Rivers and Creeks
Bibliographic record
Abstract
Abstract Perfluorinated alkyl acids (PFAs) belong to a family of chemicals that are highly persistent and potentially ecotoxic. They are under scrutiny by government agencies who must determine their risk to humans and the environment. Numerous studies have measured perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in selected areas of the world, but there has been no systematic cross-Canada study of these compounds in surface waters. This report describes the concentrations of PFAs in 38 rivers across Canada (42 to 60°N and 62 to 136°W). Samples were collected upstream and downstream of populated areas. PFOS and PFOA were the predominant PFAs detected. Values of PFOS ranged from <0.020 to 34.6 ng/L and PFOA ranged from 0.044 to 9.9 ng/L. Highest concentrations occurred in areas of high population densities, generally at downstream sites. The shorter chain perfluorocarboxylates (PFCAs) (C6)to C9) were present in most samples but the longer chain PFCAs (C10 to C14) were not often detected. Perfluorohexane sulfonate was the next most frequently detected perfluoroalkylsulfonate while perfluoro-1-octanesulfonamide (PFOSA) was detected infrequently.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.002 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".