Fractionation and Bioaccumulation of Perfluorooctane Sulfonate (PFOS) Isomers in a Lake Ontario Food Web
Bibliographic record
Abstract
The environmental ubiquity of perfluorooctane sulfonate (PFOS) is well-known. However, little is known about the environmental fate of individual PFOS isomers. In this study, we investigated the fractionation and the bioaccumulation of PFOS isomers in water, sediment and biota collected from Lake Ontario. A total of six isomers, three perfluoro-monomethyl-substituted compounds, and three perfluoro-dimethyl isomers in addition to the linear PFOS (L-PFOS) were detected in water, sediment and biota. L-PFOS represented a much higher proportion of total PFOS (sum of linear and branched) in all organisms (>88%) compared to its proportion in technical PFOS (77%). The predominance of L-PFOS suggests a reduced uptake of branched isomers, a more rapid elimination of the branched isomers and/or a selective retention of the L-PFOS. The PFOS isomer profile found in biota was very similar to sediment, even for pelagic organisms such as zooplankton, suggesting greater partitioning of L-PFOS to biota and to sediment. The bioaccumulation factor (BAF) for L-PFOS between lake trout (whole fish) and water was estimated to be 3.4 x 10(4) L/kg compared with 2.9 x 10(3) L/kg for the monomethyl-substituted group (MM-PFOS). The remarkable difference between L-PFOS and branched isomer BAFs is due to an enrichment of branched isomers in water. The trophic magnification factor of L-PFOS (4.6 +/- 1.0) was greater than MM-PFOS isomers (1.3 +/- 0.17 to 2.6 +/- 0.51), whereas dimethyl-PFOS showed no biomagnification. The results illustrate the important influence of molecular structure on the bioaccumulation of perfluoroalkyl sulfonates.
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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 | 0.000 |
| 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 | 0.000 |
| 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".