Environmental Reactions of Novel and Legacy Fluorosurfactants
Bibliographic record
Abstract
Per- and polyfluoroalkyl substances (PFAS) are a class of environmental contaminants grouped together by the presence of a perfluoroalkyl moiety. PFAS have a range of applications depending on their specific chemical structure including as direct-use surfactants. Due to concerns about persistence, bioaccumulation potential, and toxicity, some PFAS have been phased-out and replaced with new PFAS. This thesis explores the environmental fate of one phased-out fluorosurfactant, and one novel fluorosurfactant and its synthetic intermediate. Perfluoroalkyl phosphinic acids (PFPiAs) are fluorosurfactants that were used as wetting and levelling agents and as defoaming additives to pesticide formulations. Male Sprague-Dawley rats were dosed with C6/C8 PFPiA or C8/C8 PFPiA, which were metabolized to form persistent perfluoroalkyl phosphonic acids (PFPAs), and 1H-perfluoroalkanes (1H-PFAs), which contain one labile hydrogen that may undergo further metabolism. This was the first reported cleavage of a C-P bond in mammals, and the first attempt to characterize the degradation of any perfluoroalkyl acid. A new fluorosurfactant on the market was designed with the intention that it would degrade in the environment to non-bioaccumulative components. The surfactant diFESOS, and its semi-volatile synthetic intermediate FESOH were investigated. Atmospheric oxidation experiments of FESOH reported a short lifetime with respect to reaction with OH radicals. FESOH undergoes multiple defluorination steps to form products with fewer fluorine atoms, including perfluoropropanoic acid (PFPrA) as the terminal aqueous phase product. The surfactant diFESOS, FESOH, and another major degradation product were incubated with activated sludge from a wastewater treatment plant to assess aerobic microbial degradation. Ultimately, diFESOS degraded to lower fluorinated acidic PFAS, including small amounts of PFPrA. The formation of the metabolite 2H-3:2 PFECA is hypothesized to occur via defluorination on a carbon adjacent to the sulfur atom, which we believe has not been previously reported. Overall, major metabolites have lower bioaccumulation potential than the parent diFESOS surfactant. These laboratory studies enable understanding of environmental fate of these specific PFAS, and also contribute to fundamentally understanding the reactivity of highly fluorinated molecules, which may allow for the design of chemicals that can harness the functionality of organofluorine without persisting in the environment.
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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".