Sorption of Polyfluoroalkyl Surfactants on Surface Soils: Effect of Molecular Structures, Soil Properties, and Solution Chemistry
Why this work is in the frame
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Bibliographic record
Abstract
Zwitterionic, cationic, and anionic per- and polyfluoroalkyl substances (PFASs) are identified in aqueous film-forming foam (AFFF) concentrates and AFFF-impacted sites. However, the mobility potential of zwitterionic and cationic PFASs is poorly understood, preventing reliable site assessment. The study aimed to elucidate the mobility behaviors of PFASs of various charge states in saturated soil–water systems and assess critical influencing factors. Five anionic, three zwitterionic, and one cationic PFASs were investigated in five soils through batch sorption experiments. Pairwise comparison revealed that the quaternary ammonium group imparted a strong affinity of cationic perfluorooctaneamide ammonium compound (PFOAAmS) for soils. The influence of the quaternary ammonium group is mitigated in polyfluoroalkyl betaines, yet perfluorooctane sulfonamidoalkyl betaine (PFOSB) showed strong sorption in selected soils. Two soil bulk properties showed some correlations with the soil–water distribution coefficient (Kd). A positive correlation with the fraction of soil organic carbon was found only for anionic PFASs, whereas cation exchange capacity had an approximate positive correlation with Kd only for PFOAAmS. Water chemistry (Ca2+ and pH) influences the sorption of nonanionic PFASs in very distinct fashions or even in opposite trends to what was known for anionic PFASs. Sorption was insensitive to pH changes except for PFOSB; PFOSB underwent profound sorption reduction because its speciation occurs around neutral pH, while the two other betaines and PFOAAmS have pKa values that are outside of the environmentally relevant range. The lack of correlations suggests that the transport potential of PFASs is probably highly site-specific. It remains a challenge in deciphering PFAS sorption mechanisms and predicting how AFFF plumes migrate.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| Science and technology studies | 0.000 | 0.004 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it