Modeling the Influence of Coastal Site Characteristics on <scp>PFAS</scp> in Situ Remediation
Bibliographic record
Abstract
Abstract The potential performance of a hypothetical colloidal‐activated carbon (CAC) in situ remedy for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in groundwater in coastal zones was evaluated using estimated hydrogeologic and geochemical parameters for a coastal site in the United States. With these parameters, a reactive transport model (ISR‐MT3DMS) was used to assess the effects of tidal fluctuations and near‐shore geochemistry on CAC performance. The average near‐shore ionic strength of 84 mM at the site was conservatively estimated to result in an increase in the adsorption of PFOA to CAC by about 50% relative to non‐coastal sites with ionic strength <10 mM. The modeling also confirmed the hypothesis that tidally induced groundwater flow reversals near the shore would result in the accumulation of PFOA at the downgradient edge of the CAC zone. Slow desorption of PFOA from this downgradient CAC boundary may sustain downgradient plume concentrations above a strict cleanup criterion (e.g., USEPA MCL of 0.004 μg/L), for decades; however, there was still a large PFOA mass flux reduction (>99.9%) achieved after several decades at the shore. CAC longevity was substantially greater for PFOS with a similar source concentration; however, the higher PFOS distribution coefficient ( K d ) in soil downgradient from the CAC zone resulted in substantially longer flushing times. It is recommended that short‐term remedial action objectives for CAC remedies at coastal sites be based on mass flux reduction targets over a period of several decades, given the demonstrated challenges in trying to achieve very low cleanup criteria downgradient of a CAC zone in the short term.
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How this classification was reachedexpand
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 | 0.000 |
| 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) | 0.000 | 0.001 |
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 teacher head, 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".