Uptake and transformation of per- and polyfluoroalkyl substances from aqueous film-forming foams in concrete
Bibliographic record
Abstract
The significant environmental occurrence of per- and polyfluoroalkyl substances (PFAS)due to their ubiquity in many consumer and industrial products combined with their potentiallyharmful health effects has caused increased attention from regulators in recent years. Asignificant source of PFAS contamination is the utilization of aqueous film-forming foams(AFFF) in combatting class B fires at airports, military bases, and firefighter training facilities.Extensive research has investigated PFAS contamination across solid and aqueous matrices,encompassing surface water, wastewater, groundwater, biosolids, and soils. Contamination ofconcrete – an often-overlooked matrix and potential PFAS source – remains underexplored,particularly at military bases and airports. As a ubiquitous construction material globally,concrete is directly exposed to AFFF during training exercises, particularly in the form of groundslabs at impacted sites. Limited studies examining concrete from these sites have revealedsubstantial PFAS presence stemming from both electrochemical fluorination (ECF)-based andfluorotelomer (FT)-based AFFFs, highlighting concrete's potential for long-term PFAS leachingeven years after AFFF activities have ceased. Numerous questions persist regarding AFFFcontamination of concrete, including diffusion rates, the influence of AFFF additives, andconcrete-PFAS chemical interactions, warranting further investigation. This thesis aims tounderstand the physicochemical interactions between concrete and AFFF under conditionsmimicking those at impacted sites to better understand the ultimate fate of PFAS upon initialexposure to concrete in the environment.First, laboratory-based experiments were conducted to assess the artificial PFAScontamination of concrete using individual PFAS and ECF AFFF. Evaluation of PFAS uptake inconcrete encompassed flat finished surfaces and chipped surfaces to simulate aged concretevariability. Additionally, various PFAS within an AFFF mix, including dominantperfluorosulfonic acids (PFSAs) and precursors, were examined using high-resolution massspectrometry. Analysis of PFAS and AFFF solutions pooled onto concrete surfaces revealed nosignificant concentration decrease, while examination of powder from lab-contaminated coresindicated PFAS diffusion primarily within the top 0.5 cm of the core, with faster penetrationobserved in chipped surface concrete compared to flat surface. The contradiction was becausePFAS mass in concrete cores only represented a small fraction (1.3% to 10.8%, mean 3.9%) ofinitial spiked PFAS. A correlation between decreasing PFAS chain length and increased mobilityor diffusivity through cores was evident, suggesting that AFFF additives influence PFASdiffusion in concrete. Furthermore, intermittent wetting and drying cycles accelerated PFASpenetration, albeit equally for PFAS of differing chain lengths, probably due to the wickingeffect. Cores from a Canadian military base contained a mix of ECF and FT PFAS, with 6:2fluorotelomer sulfonate (6:2 FTSA) being most abundant in the top 1 cm of the core, withperfluoroctanesulfonic acid (PFOS) being dominant throughout the rest of the core suggesting arecent switch from ECF to FT foams.A comprehensive extraction method for PFAS from AFFF-affected concrete, validatedthrough spike-recovery trials, was also developed in this work. Seven solvent conditions wereassessed for their efficiency in extracting perfluoroalkyl acids (PFAAs) and 14 distinct precursorclasses present in ECF-based AFFF-contaminated concrete powder. Methanol with 100 mMammonium acetate was the optimal solvent for extracting a broad spectrum of anionic, cationic,and zwitterionic compounds, although other solvent conditions exhibited comparable recoveryrates for most PFAS. Recovery analysis of perfluorocarboxylic acids (PFCAs), perfluoroalkylsulfonamides (FASAs), and perfluoroalkyl amido amines (PFAAAm) compounds indicated highrecoveries for PFCAs and FASAs, contrasting with notably low recoveries for PFAAAmcompounds, implying rapid degradation of amide-containing precursors during extraction. Thisdegradation mechanism was attributed to alkaline hydrolysis facilitated by calcium hydroxideleaching from concrete. Additionally, investigations into sulfonamide precursors suggestedsalting-out effects rather than compound degradation as the primary cause for their rapidconcentration decrease.This work provides important findings on the kinetics of uptake of PFAS into concretefrom AFFF, as well as potential transformations that can occur at concrete-water interfaces,within concrete, and during extraction
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".