Interactions between Per- and Polyfluoroalkyl Substances (PFAS) at the Water–Air Interface

Environmental Science & Technology, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 21, 2025

Per- and polyfluoroalkyl substances (PFAS)─so-called "forever chemicals"─contaminate the drinking water of about 100 million people in U.S. alone are inefficiently removed by standard treatment techniques. A key property these compounds that underlies their fate transport efficacy several promising remediation approaches is they accumulate at water–air interface. This phenomenon remains incompletely understood, particularly under conditions relevant to natural systems where interfaces often carry significant loads other organic contaminants or matter. To understand impact loading on PFAS adsorption, we carried out molecular dynamics simulations varying interfacial densities. We find adsorbed form strong mutual interactions (attraction between perfluoroalkyl chains electrostatic among charged head groups) give rise ordered coatings. These involve near-cancellation hydrophobic attraction Coulomb repulsion. Our findings explain an apparent paradox whereby adsorption isotherms suggest minimal while simultaneously displaying a high sensitivity composition density Consideration present with interface has potential allow for more accurate predictions design efficient approaches.

Language: Английский

---

Mass-Based, Field-Scale Demonstration of PFAS Retention within AFFF-Associated Source Areas

Environmental Science & Technology, Journal Year: 2020, Volume and Issue: 54(24), P. 15768 - 15777

Published: Dec. 3, 2020

Transport of poly- and perfluoroalkyl substances (PFAS) at aqueous film-forming foam (AFFF)-impacted sites is limited by various processes that can retain PFAS mass within the source area. This study used concentration data obtained via a high-resolution sampling analytical protocol to estimate distribution in downgradient areas former firefighter training The total present site was approximately 222 kg, with 106 kg as acids (PFAAs) 116 polyfluorinated precursors. Zwitterionic cationic represented 83% precursor were found primarily up/side-gradient (75%), likely due preferential hydrophobic partitioning, electrostatic interactions, diffusion into lower-permeability soils. Based on release history high percentage precursors (primarily electrochemical fluorination-derived compounds), estimated conversion rate PFAAs less than 2% annually. Eighty-two percent encountered soils, which potential for advection transformation. contributed 99% decrease discharge far-downgradient plume (0.048 kg/yr compared near-source area (3.6 kg/yr)). results provide field-scale evidence importance these retention where AFFF has been released.

Language: Английский

---

Per- and Polyfluoroalkyl Substances in Contaminated Soil and Groundwater at Airports: A Canadian Case Study

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 56(2), P. 885 - 895

Published: Dec. 30, 2021

The occurrence of 93 classes per- and polyfluoroalkyl substances (PFASs) was investigated at aqueous film-forming foam (AFFF)-impacted sites four Canadian airports. Surface/subsurface soil groundwater samples were characterized using high-resolution mass spectrometry (HRMS) an improved total oxidizable precursor (TOP) assay. PFAS profiles, loads, spatial trends highly site-specific, influenced by the AFFF use history, variations in sorption, transport, situ transformation potential PFASs. All have been impacted more than one chemistry, with active firefighter training area exhibiting a greater variety burden decommissioned sites. Zwitterionic cationic compounds composed large percentage (34.5-85.5%) most surface source zone but relatively low (<20%) samples. Background soils surrounding contained predominantly unidentified precursors attributed to atmospheric deposition, while AFFF-impacted soils, originating from AFFFs can be largely captured HRMS available suspect lists. Horizontal transfer PFASs limited, vertical migration down column occurred even locations permeability. This study provides critical data set support developing new priority analyte lists integrating TOP assay for comprehensive monitoring

Language: Английский

---

Unsaturated PFOS and Other PFASs in Human Serum and Drinking Water from an AFFF-Impacted Community

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(12), P. 8139 - 8148

Published: May 24, 2021

Understanding how exposure to aqueous film-forming foam (AFFF)-impacted drinking water translates bioaccumulation of per- and polyfluoroalkyl substances (PFASs) is essential assess health risks. To investigate spatial variability PFAS in communities near an AFFF source zone, blood serum was collected 2018 from 220 adult residents El Paso County (Colorado), as were raw samples several wells. C6 C8 perfluoroalkyl sulfonates (PFSAs) predominant water. PFASs most elevated the district nearest zone (median ∑PFSA 618 ng/L 33 ng/mL serum). A novel PFAS, unsaturated perfluorooctane sulfonate, detected >80% at low concentrations (≤1.9 Drinking wells displayed increased prevalence sulfonamide precursors not serum. Serum-to-water ratios greatest for long-chain least impacted district. Additional a subset study participants June 2019 showed that declined after ceased, although declines perfluoropentane sulfonate minimal. Our findings demonstrate AFFF-impacted are exposed complex, spatially variable mixtures PFASs.

Language: Английский

---

Environmental Sources, Chemistry, Fate, and Transport of Per‐ and Polyfluoroalkyl Substances: State of the Science, Key Knowledge Gaps, and Recommendations Presented at the August 2019 SETAC Focus Topic Meeting

Environmental Toxicology and Chemistry, Journal Year: 2021, Volume and Issue: 40(12), P. 3234 - 3260

Published: July 29, 2021

Abstract A Society of Environmental Toxicology and Chemistry (SETAC) Focused Topic Meeting (FTM) on the environmental management per‐ polyfluoroalkyl substances (PFAS) convened during August 2019 in Durham, North Carolina (USA). Experts from around globe were brought together to critically evaluate new emerging information PFAS including chemistry, fate, transport, exposure, toxicity. After plenary presentations, breakout groups established tasked identify adjudicate via panel discussions overarching conclusions relevant data gaps. The present review is one a series summarizes outcomes presentations related (1) primary sources pathways environment, (2) sorption transport porous media, (3) precursor transformation, (4) practical approaches assessment source zones, (5) standard novel analytical methods with implications for forensics site management, (6) classification grouping multiple perspectives. Outcomes illustrate that will continue be challenge, additional pressing needs include increased availability standards fate transformation. Although state science sufficient support degree site‐specific flexible risk effective prioritization tools, predictive models, improved standardized are needed guide broader policies best practices. Environ Toxicol Chem 2021;40:3234–3260. © 2021 Authors. published by Wiley Periodicals LLC behalf SETAC.

Language: Английский

---

Environmental Source Tracking of Per- and Polyfluoroalkyl Substances within a Forensic Context: Current and Future Techniques

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(11), P. 7237 - 7245

Published: May 13, 2021

The source tracking of per- and polyfluoroalkyl substances (PFASs) is a new increasingly necessary subfield within environmental forensics. We define PFAS as the accurate characterization differentiation multiple sources contributing to contamination in environment. should employ analytical measurements, multivariate analyses, an understanding fate transport framework conceptual site model. Converging lines evidence used differentiate include: identification PFASs strongly associated with unique sources; ratios homologues, classes, isomers at contaminated site; site's hydrogeochemical conditions. As field progresses, development standards wider availability high-resolution mass spectral data will enhance currently available capabilities. In addition, computational tools, including unsupervised (i.e., exploratory) supervised predictive) machine learning techniques, may lead novel insights that targeted list be useful for tracking. this Perspective, we identify current tools principal developments enable greater confidence apportion sources.

Language: Английский

---

An Investigation of Thermal Air Degradation and Pyrolysis of Per- and Polyfluoroalkyl Substances and Aqueous Film-Forming Foams in Soil

ACS ES&T Engineering, Journal Year: 2022, Volume and Issue: 2(2), P. 198 - 209

Published: Jan. 11, 2022

In this study, we found that thermal decomposition of per- and polyfluoroalkyl substances (PFAS) in soil was rapid at moderate temperatures 400–500 °C, regardless whether the contaminated by a single PFAS compound or mixture aqueous film-forming foams. Substantial degradation (>99%) soil, including perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), short-chain homologues, cationic zwitterionic precursors, PFOA PFOS alternatives, occurred 30 min 500 °C both sealed reactor air horizontal under continuous flow N2. The effect initial level (0.001–10 μmol/g) texture insignificant, provided sufficiently high temperature applied. Furthermore, study showed, for first time, kaolinite dramatically decreased apparent yield F from heated >300 likely due to chemisorption radicals on kaolinite. This phenomenon not observed when an inorganic fluoride salt (NaF) were thermally treated. Lastly, various nonpolar products reported time. profile fluorinated volatiles, particularly perfluoroalkenes, similar between these two chemicals. results support radical-mediated pathway PFAS.

Language: Английский

---

Release of Per- and Polyfluoroalkyl Substances from Aqueous Film-Forming Foam Impacted Soils

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(21), P. 14617 - 14627

Published: Oct. 19, 2021

Per- and polyfluoroalkyl substances (PFASs) are highly mobile in the saturated subsurface, yet aqueous film-forming foam (AFFF)-impacted source zones appear to be long lasting PFAS reservoirs. This study examined release of over one hundred anionic zwitterionic PFASs from two AFFF-impacted surface soils under conditions with packed soil columns. Perfluoroalkyl acids (PFAAs) were released more rapidly than their polyfluorinated precursors, while that present partially uncharged states slowly entirely as anions, terminal cationic functional groups when compared analogous zwitterions only groups. Nonideal transport was observed both per- classes, column effluent concentrations increased by up 107-fold sustained artificial groundwater flow. A flow-interruption experiment suggested influence rate-limited desorption on diverse including PFAAs few four perfluorinated carbons. These results suggest during infiltration slow, PFAA precursors may result these compounds comprising an increasingly large fraction remaining soils.

Language: Английский

---

Thermal Decomposition of Anionic, Zwitterionic, and Cationic Polyfluoroalkyl Substances in Aqueous Film-Forming Foams

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(14), P. 9885 - 9894

Published: July 8, 2021

In this study, we investigated thermal decomposition mechanisms of cationic, zwitterionic, and anionic polyfluoroalkyl substances, including those present in aqueous film-forming foam (AFFF) samples. We novel evidence that substances gave quantitative yields perfluoroalkyl different chain lengths during treatment. The results support a radical-mediated transformation mechanism involving random-chain scission end-chain scission, leading to the formation carboxylic acids such as perfluorooctanoic acid (PFOA) from certain amides sulfonamides. Our also direct (chain stripping) on nonfluorinated moiety sulfonamides, resulting perfluorooctanesulfonic (PFOS) other structurally related compounds. Thermal 8:2 fluorotelomer sulfonate occurred through recombination reactions, successively yielding PFOS. All studied began degrade at 200-300 °C, exhibiting near-complete ≥400 °C. Using high-resolution parent ion search method, demonstrated for first time low-temperature treatments AFFF samples led generation fluoroalkyl perfluoroheptanesulfonamide, sulfonic acid, N-methyl perfluorooctane sulfonamide, previously unreported compound N-2-propenyl-perfluorohexylsulfonamide. This study provides key insights into fate processes.

Language: Английский

---

Perfluoroalkyl acids on suspended particles: Significant transport pathways in surface runoff, surface waters, and subsurface soils

Journal of Hazardous Materials, Journal Year: 2021, Volume and Issue: 417, P. 126159 - 126159

Published: May 19, 2021

Eroded particles from the source zone could transport a high concentration of perfluoroalkyl acids (PFAAs) to sediments and water bodies. Yet, contribution suspended has not been systematically reviewed. Analyzing reported studies, we quantitatively demonstrate that in surface can contain significantly higher concentrations PFAAs than sediment below, indicating are but eroded carried upstream. The affinity depends on particle composition, including organic carbon fraction iron or aluminum oxide content. In soils, most retained within top 5 m below ground surface. distribution subsurface varies based site properties local weather conditions. depth corresponding maximum PFAA soil decreases with an increase rainfall amount received catchment areas. We attribute greater accumulation near upper layer zones upstream receiving heavy rainfall. Precursor transformation aerobic is anaerobic zone, thereby making serve as long-term groundwater pollution. Collectively, these results suggest particles, often overlooked vector for PFAAs, be dominant pathway environments.

Language: Английский

---