Occurrence and fate of perfluoroalkyl contaminants in the abiotic environment
Bibliographic record
Abstract
The observation of PFCs in the Canadian Arctic environment confirmed that long-range transport of FTOHs and FSAs is occurring. PFSAs, PFSAs and known PFC precursor degradation products were observed in water and sediment of three arctic lakes and atmospheric particles. Evidence also indicated that small-scale local contamination of PFCs has occurred in the Arctic. Vapour pressures measurements of the fluorinated telomer alcohols (FTOHs) confirmed the volatile nature of this class of PFCs. Comparison of measured values with physical property estimation models indicated that the unique geometry of PFCs is important in understanding the environmental fate of these contaminants. Given the ubiquitous nature of perfluoroalkyl contaminants (PFCs) in wildlife and humans, the goal of this research was to investigate the occurrence and fate of PFCs in the abiotic environment, with particular emphasis on the North American atmosphere, Lake Ontario and the Canadian Arctic. Spatial and historical trends of PFSAs and PFSAs in Lake Ontario sediment were determined. Historical profiles correlated well with available production data of PFCs. A mass budget indicated that the largest sources of PFSAs and PFSAs to Lake Ontario were inflow from the Niagara River and other tributaries, while outflow via the St Lawrence River and sedimentation were important loss processes. This research indicates that direct sources contribute to the environmental burden of PFCs, and also provides evidence that indirect sources, such as the atmospheric transport of FTOHs and FSAs to remote regions and subsequent degradation to PFSAs and PFSAs, are also important. Air sampling campaigns established that FTOHs and polyfluorinated sulfonamides (FSAs), precursors of perfluorosulfonates (PFSAs) and perfluorocarboxylates (PFSAs), are widely distributed in the North American atmosphere, including the Canadian Arctic. Larger concentrations were identified near possible point sources and long-term temporal trends (2002-2005) from samples collected in Toronto Ontario indicated that atmospheric concentrations of FTOHs and FSAs were constant throughout the sampling period.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 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".