Environmental Chemistry of Perfluoroalkyl and Polyfluoroalkyl Substances in Aqueous Film Forming Foams
Bibliographic record
Abstract
While aqueous film forming foam (AFFF) release has been known to result in environmental contamination with perfluoroalkyl and polyfluoroalkyl substances (PFASs) for over fifteen years, identities of individual PFASs in AFFFs have been largely unknown, proprietary information. Using mixed-mode ion exchange solid phase extraction (SPE), high resolution mass spectrometry (HR-MS), quadrupole time-of-flight (qTOF) tandem mass spectrometry (MS/MS), and liquid chromatography (LC)-MS/MS, 103 individual PFASs were identified in AFFFs and surfactant concentrates, including multiple chain-length congeners. Aerobic wastewater treatment plant sludge biodegradation of two AFFF components, 6:2 fluorotelomer sulfonamide alkylbetaine (FTAB) and alkylamine (FTAA), was investigated revealing biodegradation to short-chain perfluoroalkyl carboxylates (PFCAs) and known PFCA precursors. Additional degradation products were also identified, including 6:2 fluorotelomer sulfonamide (FTSAm) as a degradation product of both 6:2 FTAB and 6:2 FTAA, and six additional degradation products of 6:2 FTAA. A survey of selected Canadian surface waters for AFFF-related PFASs using SPE and LC-MS/MS revealed that several AFFF-related PFASs could be detected in urban and AFFF-impacted surface waters. These included FTABs and fluorotelomer betaines (FTBs), which were the fluorotelomer PFASs with the highest maximum concentrations. Other PFASs, such as perfluorohexane sulfonamide (FHxSA), 6:2 FTSAm, and 6:2 fluorotelomer mercaptoalkylamido sulfonate sulfone (FTSAS-SO2) were identified in some samples. Extraction and analysis of sediment from an AFFF-impacted river and batch sorption experiments with 6:2 FTAA and 6:2 FTAB in an agricultural soil provide preliminary insights into sorption behaviour of AFFF components, where longer chain-length FTBs were apparently more sorptive than shorter chain-lengths and 6:2 FTAA was more sorptive than 6:2 FTAB. This work is significant in identifying numerous PFASs found in AFFF that require further research in regards to their environmental fate and toxicology, demonstrating the presence of AFFF-related PFASs in Canadian environmental samples, and investigating biodegradation forming PFCAs and sorption of selected PFASs found in AFFFs.
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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 | 0.000 | 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) | 0.001 | 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".