Aqueous Film-forming Foam Research Articles

Определение критической толщины пенного слоя для локализации и ликвидации пламенного горения проливов сжиженного природного газа

PURPOSE. Increasing attention has been paid recently to applying high-expansion foam as means of localizing and eliminating liquefied natural gas spills flaming combustion. Scientific sources widely discuss the issues of foam expansion rate and elasticity, critical intensity of its supply and application rate. However, critical foam layer thickness is underestimated. At the same time one of the reasons for fire-fighting foam low efficiency is precisely the difficulty in providing required foam layer thickness. The purpose of this publication is to assess relationship between critical foam layer thickness and main parameters of localizing and eliminating liquefied natural gas flaming combustion. METHODS. Review of scientific works covering the issue of flammable liquids and liquefied natural gas foam fire extinguishment has been carried out. Methods for providing required foam layer thickness and determining foam fire extinguishing efficiency are analyzed. Results of researchers’ own experiments have been discussed, taking into account international and domestic experience in conducting similar studies. FINDINGS. Based on researchers’ own experimental data analysis, taking into account information from scientific sources, critical foam layer thickness assessment has been made for foams of various expansions used to localize and eliminate liquefied natural gas spills flaming combustion. Approximate foam layer thickness in centimeters should be at least a quarter of high-expansion foam expansion value. RESEARCH APPLICATION FIELD. The results obtained provide general understanding that to ensure efficiency of liquefied natural gas flaming combustion localization and elimination, it is necessary to ensure not only appropriate foam expansion and application rate, but also required foam layer thickness. The results can be used in scientific research and educational process, as well as by fire services and emergency rescue units in elimination of accidents accompanied by liquefied natural gas spills flaming combustion. CONCLUSIONS. Foam layer thickness is the key parameter for liquefied natural gas spills foam fire extinguishment and providing controlled burning technology. Depending on foam supply intensity the necessary condition for providing liquefied natural gas flaming combustion localization and elimination is to achieve or exceed critical foam layer thickness. Critical foam layer thickness depends on foam expansion ratio. As foam expansion ratio increases, critical foam layer thickness rises, its value can exceed two or more meters.

PFAS in the Drinking Water Source: Analysis of the Contamination Levels, Origin and Emission Rates

Groundwater contamination caused by the use of the aqueous film-forming foam (AFFF) containing per- and polyfluoroalkyl substances (PFAS) was investigated in southern Sweden. ΣPFAS concentrations in groundwater ranged between 20 and 20,000 ng L−1; PFAS composition was primarily represented by PFOS and PFHxS. The PFAS chain length was suggested to have an impact on the contaminant distribution and transport in the groundwater. PFAS profiling showed that the use of PFSAs- and PFCAs/FTSAs-based PFAS-AFFF can be a contributor to PFAS contamination of the drinking water source (groundwater). PFAS emission was connected to PFAS-AFFF use during the fire-training and fire-fighting equipment tests at the studied location. PFAS emission per individual fire training was (semi-quantitatively) estimated as [1.4 < 11.5 ± 5.7 < 43.7 kg] (n = 20,000). The annual emission estimates varied as [11 < 401 ± 233 < 1125 kg yr−1] (n = 1005) considering possible [2 < 35 ± 20 < 96] individual fire-training sessions per year.

Impacts of Environmental and Engineered Processes on the PFAS Fingerprint of Fluorotelomer-Based AFFF.

Forensic analysis can potentially be used to determine per- and polyfluoroalkyl substance (PFAS) sources at contaminated sites. However, fluorotelomer aqueous film-forming foam (AFFF) sources are difficult to identify because the polyfluorinated active ingredients do not have authentic standards and because the parent compounds can undergo transformation and differential transport, resulting in alteration of the PFAS distribution or fingerprint. In this study, we investigate changes in the PFAS fingerprint of fluorotelomer-derived AFFF due to environmental and engineered processes, including groundwater transport, surface water flow, and land application of contaminated biosolids. Fingerprint analysis supplemented by quantification of precursors and identification of suspected active ingredients shows a clear correlation between a fluorotelomer AFFF manufacturer and surface water of nearby Lake Michigan, demonstrating contamination (>100 ng/L PFOA) of the lake due to migration of an AFFF-impacted groundwater plume. In contrast, extensive processing during wastewater treatment and environmental transport results in large changes to the AFFF fingerprint near agricultural fields where contaminated biosolids were spread. At biosolids-impacted sites, the presence of active ingredients confirms contamination by fluorotelomer AFFF. While sediments can retain longer-chain PFAS, this study demonstrates that aqueous samples are most relevant for PFAS fingerprinting in complex sites, particularly where shorter-chain compounds have been used.

Perfluoroalkyl substances exposure in firefighters: Sources and implications

Firefighters are at risk of occupational exposure to long-chain per- and poly-fluoroalkyl substances (PFASs), most notably from PFASs present in Class B aqueous film-forming foam (AFFF). Firefighters have been found to have elevated serum levels of long-chain PFASs. Due to the persistence of PFAS chemicals in the human body and their ability to bioaccumulate, firefighters experience the latent and cumulative effects of PFAS-containing AFFF exposure that occurs throughout their careers. This article summarizes the history of AFFF use by firefighters and current AFFF use practices. In addition, this paper describes PFAS levels in firefighter serum, PFAS serum removal pathways, PFAS exposure pathways, and occupational factors affecting PFAS levels in firefighters. International, national, and state agencies have concluded that PFOA, a long-chain PFAS, is potentially carcinogenic and that carcinogens have an additive effect. From the cancer types that may be associated with PFAS exposure, studies on cancer risk among firefighters have shown an elevated risk for thyroid, kidney, bladder, testicular, prostate, and colon cancer. Thus, exposure to PFAS-containing AFFF may contribute to firefighter cancer risk and warrants further research.

Assessing aerobic biotransformation of 8:2 fluorotelomer alcohol in aqueous film-forming foam (AFFF)-impacted soils: Pathways and microbial community dynamics

Production of 8:2 fluorotelomer alcohol (8:2 FTOH) for industrial and consumer products, including aqueous film-forming foams (AFFFs) used for firefighting, has resulted in its widespread occurrence in the environment. However, the fate of 8:2 FTOH at AFFF-impacted sites remains largely unknown. Using AFFF-impacted soils from two United States Air Force Bases, microcosm experiments evaluated the aerobic biotransformation of 8:2 FTOH (extent and byproduct formation) and the dose-response on microbial communities due to 8:2 FTOH exposure. Despite different microbial communities, rapid transformation of 8:2 FTOH was observed during a 90-day incubation in the two soils, and 7:2 secondary fluorotelomer alcohol (7:2 sFTOH) and perfluorooctanoic acid (PFOA) were detected as major transformation products. Novel transformation products, including perfluoroalkane-like compounds (1H-perfluoroheptane, 1H-perfluorohexane, and perfluoroheptanal) were identified by liquid chromatography-high resolution mass spectrometry (LC-HRMS) and used to develop aerobic 8:2 FTOH biotransformation pathways. Microbial community analysis suggests that species from genus Sphingomonas are potential 8:2 FTOH degraders based on increased abundance in both soils after exposure, and the genus Afipia may be more tolerant to and/or involved in the transformation of 8:2 FTOH at elevated concentrations. These findings demonstrate the potential role of biological processes on PFAS fate at AFFF-impacted sites through fluorotelomer biotransformation.

Ultrasound-enhanced Magnéli phase Ti4O7 anodic oxidation of per- and polyfluoroalkyl substances (PFAS) towards remediation of aqueous film forming foams (AFFF)

Per-and polyfluoroalkyl substances (PFAS) remediation is still a challenge. In this study, we propose a hybrid system that combines electrochemical treatment with ultrasound irradiation, aiming for an enhanced degradation of PFAS. Equipped with a titanium suboxide (Ti4O7) anode, the electrochemical cell is able to remove perfluorooctanoic acid (PFOA) effectively. Under the optimal conditions (50 mA/cm2 current density, 0.15 M Na2SO4 supporting electrolyte, and stainless steel/Ti4O7/stainless steel electrode configuration with a gap of ∼10 mm), the electrochemical process achieves ∼100 % PFOA removal and 43 % defluorination after 6 h. Applying ultrasound irradiation (130 kHz) alone offers a limited PFOA removal, with 33 % PFOA removal and 5.5 % defluorination. When the electrochemical process is combined with ultrasound irradiation, we observe a significant improvement in the remediation performance, with ∼100 % PFOA removal and 63.5 % defluorination, higher than the sum of 48.5 % (43 % achieved by the electrochemical process, plus 5.5 % by the ultrasound irradiation), implying synergistic removal/oxidation effects. The hybrid system also consistently shows the synergistic defluorination during degradation of other PFAS and the PFAS constituents in aqueous film forming foam (AFFF). We attribute the synergistic effect to an activated/cleaned electrode surface, improved mass transfer, and enhanced production of radicals.

Effect of temperature on stability and film thinning behavior of aqueous film forming foam

In the extinguishing process, the stability of the foam extinguishing agent would be inevitably affected by the flame with high temperature, which has an impact on the effectiveness of the foam. Therefore, it is crucial to investigate the effect of temperature on the stability of foam. The prior research related with the foam stability has mainly concentrated on foam drainage and foam height. However, the details of foam stability have only been the subject of a few studies. In this paper, the effect of temperature on stability and film thinning behavior of aqueous film forming foam (AFFF) were studied using microscope and the optical interferometry device, where the bubble sizes, the film thinning rate and the film lifetime were measured and analysed. The results show that the foam stability and foam film stability were influenced by temperature significantly. The foam lifetime was discovered to decrease exponentially with the increase of temperature, showing that the foam became unstable under higher temperature. Besides, the predicted model of film thickness under different temperature was induced and verified, where the effect of temperature on the foam fluid viscosity was considered. It was also found that the film lifetime decreased exponentially with the increase of temperature, which was caused by the changing in the film surface adsorption, film surface elasticity and the film viscosity under higher temperature.

Experimental methods for studying heat transfer in cable penetrations in case of fire

An experimental technique for studying the processes of heat transfer in cable penetrations under the thermal effects of fire is proposed. To study the influence of the design of cable penetrations on cable heating processes, three most common types of penetrations were selected. New experimental data on the dependence of the temperature of the structural elements of the cable and the penetration on time have been obtained. It is shown that the conductive core of the cable is the main element involved in the propagation of heat. The presence of an air space or a material that promotes intensive heat exchange in the cable penetration design leads to an increase in its fire resistance limit. It is determined that the cable penetration with the filling of the internal space with fire-fighting foam based on polyurethane foam is most susceptible to rapid heating and loss of fire resistance. Studies have shown that when assessing the fire resistance limits of cable penetrations, it is necessary to take into account the thermophysical characteristics of cables, their number, as well as the design features of cable penetrations.

Longevity of colloidal activated carbon for in situ PFAS remediation at AFFF‐contaminated airport sites

AbstractA review of state per‐ and polyfluoroalkyl substances (PFAS) guidelines indicates that four long‐chain PFAS (perfluorooctanesulfonic acid [PFOS] and perfluorooctanoic acid [PFOA] followed by perfluorohexanesulfonic acid [PFHxS] and perfluorononanoic acid [PFNA]) are the most frequently regulated PFAS compounds. Analysis of 17 field‐scale studies of colloidal activated carbon (CAC) injection at PFAS sites indicates that in situ CAC injection has been generally successful for both short‐ and long‐chain PFAS in the short‐term (0.3–6 years), even in the presence of low levels of organic co‐contaminants. Freundlich isotherms were determined under competitive sorption conditions using a groundwater sample from an aqueous film‐forming foam (AFFF)‐impacted site. The median concentrations for these PFAS of interest at 96 AFFF‐impacted sites were used to estimate influent concentrations for a CAC longevity model sensitivity analysis. CAC longevity estimates were shown to be insensitive to a wide range of potential cleanup criteria based on modeled conditions. PFOS had the greatest longevity even though PFOS is present at higher concentrations than the other species because the CAC sorption affinity for PFOS is considerably higher than PFOA and PFHxS. Longevity estimates were directly proportional to the CAC fraction in soil and the Freundlich Kf, and were inversely proportional to the influent concentration and average groundwater velocity.

Transcriptional pathways linked to fetal and maternal hepatic dysfunction caused by gestational exposure to perfluorooctanoic acid (PFOA) or hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX) in CD-1 mice

Per- and polyfluoroalkyl substances (PFAS) comprise a diverse class of chemicals used in industrial processes, consumer products, and fire-fighting foams which have become environmental pollutants of concern due to their persistence, ubiquity, and associations with adverse human health outcomes, including in pregnant persons and their offspring. Multiple PFAS are associated with adverse liver outcomes in adult humans and toxicological models, but effects on the developing liver are not fully described. Here we performed transcriptomic analyses in the mouse to investigate the molecular mechanisms of hepatic toxicity in the dam and its fetus after exposure to two different PFAS, perfluorooctanoic acid (PFOA) and its replacement, hexafluoropropylene oxide-dimer acid (HFPO-DA, known as GenX). Pregnant CD-1 mice were exposed via oral gavage from embryonic day (E) 1.5–17.5 to PFOA (0, 1, or 5 mg/kg-d) or GenX (0, 2, or 10 mg/kg-d). Maternal and fetal liver RNA was isolated (N = 5 per dose/group) and the transcriptome analyzed by Affymetrix Array. Differentially expressed genes (DEG) and differentially enriched pathways (DEP) were obtained. DEG patterns were similar in maternal liver for 5 mg/kg PFOA, 2 mg/kg GenX, and 10 mg/kg GenX (R2: 0.46–0.66). DEG patterns were similar across all 4 dose groups in fetal liver (R2: 0.59–0.81). There were more DEGs in fetal liver compared to maternal liver at the low doses for both PFOA (fetal = 69, maternal = 8) and GenX (fetal = 154, maternal = 93). Upregulated DEPs identified across all groups included Fatty Acid Metabolism, Peroxisome, Oxidative Phosphorylation, Adipogenesis, and Bile Acid Metabolism. Transcriptome-phenotype correlation analyses demonstrated > 1000 maternal liver DEGs were significantly correlated with maternal relative liver weight (R2 >0.92). These findings show shared biological pathways of liver toxicity for PFOA and GenX in maternal and fetal livers in CD-1 mice. The limited overlap in specific DEGs between the dam and fetus suggests the developing liver responds differently than the adult liver to these chemical stressors. This work helps define mechanisms of hepatic toxicity of two structurally unique PFAS and may help predict latent consequences of developmental exposure.

Experimental Study of the Influence of Inorganic Salts on Foam Stability

The aqueous film-forming foam (AFFF) extinguishing agent is suitable for fighting various hydrocarbon fuel fires due to its dual fire-fighting effect of foam and liquid film. Because the action law and microscopic mechanism of inorganic salts on the stabilization process of surfactant-generated AFFF are not perfect, this paper employs an experimental approach to investigate the effects of inorganic salt types and concentrations on sodium dodecyl sulfate-containing foam systems (SDS). Prior to critical micelle concentration (CMC), increasing inorganic salt concentration decreased solution surface tension, but the opposite was true after CMC. The CMC value of an SDS solution decreases as inorganic salt concentration increases, and the "salting effect" of inorganic salt cations also has an effect on the CMC value. Based on the resistance of the liquid film at the gas-liquid interface affecting gas transport, the foam evolution was divided into three stages: foam generation, liquid drainage, and gas transfer. The effect of inorganic salts on these three stages was studied at the molecular level, and it was discovered that the addition of NH4Cl and MgCl2 could improve the saturation adsorption at the gas-liquid interface, reduce the surface tension of the surfactant solution, and improve foam stability. Meanwhile, inorganic salts can change the force of gas molecules, so the equilibrium force of gas across the liquid membrane increases as inorganic salt concentration increases. Additionally, the addition of inorganic salts raises the diffusive drainage coefficient, but the gravity drainage coefficient still reigns supreme in the predecay period.

Assessing the mixed foam stability of different foam extinguishing agents under room temperature and thermal radiation: An experimental study

Foam extinguishing agents have suggested to be an important method for suppressing fires, where the foam stability is one of the key factors in determining the efficiency of fire-fighting. Thus, lots of studies related to foam stability have been carried out. However, the influence of mixed types and ratios of foam agents on foam stability is still unclear. This study focuses on the foam stability of mixed foam extinguishing agents, especially under the condition of the thermal environment. The effects of mixed type and ratio on foaming ability, drainage, coarsening and insulation characteristics are studied systematically. Results indicate that the stability of mixed foam with S addition would decrease when compared with pure AFFF and FP foam, as evidenced by the decrease in foaming height, drainage time, and foam lifetime. The addition of S to AFFF or FP would produce the wetter mixed foam. In addition, the stability of AFFF/FP mixed foam first increases and then decreases with the increase of FP addition, and reaches the peak value at the mixed ratio of 3:1. The variations of foam stability could be explained by the change of viscosity and structure of adsorption layer at gas–liquid interface. The results provide helpful guidance for achieving high effective utilization of different foam extinguishing agents.

Per- and polyfluoroalkyl substances (PFAS)-free aqueous film forming foam formulations: Chemical composition and biodegradation in an aerobic environment

Per- and poly-fluoroalkyl substances (PFAS) have been historically used in fire-suppression activities, including aqueous film-forming foam (AFFF), given their unique structures and characteristics. However, the same properties that make them durable, resistant, and valuable also make them persistent, bioaccumulative, and toxic. This has led to recent investigations on alternative PFAS-free AFFF formulations for suppression of hydrocarbon-based fires. Such foams should contain certain classes of chemicals to remain effective, while being more environmentally friendly; part of the latter involves thoroughly characterizing the constituents and performing necessary biodegradability and toxicity studies. As part of the Department of Defense’s Strategic Environmental Research and Development Program (SERDP), we performed comprehensive constituents’ characterization and assessed the biodegradability of seven PFAS-free AFFF and a reference PFAS-based AFFF. We discovered that most of PFAS-free formulations share similar constituents with similar biodegradability through a 28-day reaction period. In PFAS-based AFFF, 4:2 and 6:2 fluorotelomer sulfonates (6:2 FTS) were identified with 6:2 FTS concentration at ∼ 9000 ng/mL. In biodegradation studies, the concentrations of 4:2 FTS and 6:2 FTS decreased while generating some perfluoroalkyl acids (PFCAs). These results increase the current knowledge on the biodegradability of AFFF alternatives but also highlight the need for future efforts on development of novel PFAS-free AFFF formulations that are more biodegradable than PFAS-based AFFF.

Apparent Half-Lives of Chlorinated-Perfluorooctane Sulfonate and Perfluorooctane Sulfonate Isomers in Aviation Firefighters.

Elevated levels of perfluorooctane sulfonate (PFOS) and elevated detection frequency of chloro-substituted PFOS have been reported in Australian firefighters with historical exposure to aqueous-film forming foam (AFFF). The aim of this study is to estimate the apparent half-lives of Cl-PFOS and PFOS isomers in firefighters following the end of exposure to 3M-AFFF. Paired serum samples from 120 firefighters, collected approximately five years apart, were analyzed for 8-Cl-PFOS (8-chloroperfluoro-1-octanesulfonic acid) and PFOS isomers via targeted LC-MS/MS. Apparent half-life was estimated by assuming a first order-elimination model. Cl-PFOS was detected in 93% of all initial serum samples (<LOQ-1.09 ng/mL). The average half-life of Cl-PFOS among the firefighters was 5.0 years. Branched PFOS isomers made up 55% of the total isomer concentration at the initial sampling timepoint. Five years later, the proportion of branched PFOS isomers was greater (65%). The longest average half-life (11.5 years) was estimated for "1m-PFOS". Other isomers had average half-lives ranging from 4.0 to 7.5 years. Marked differences in half-lives between PFOS isomers suggest that the elimination rate of "total PFOS" (sum of all PFOS isomers) is non-linear. This is the first study to report the serum concentrations and apparent half-life of Cl-PFOS in humans.

Per- and Poly-Fluoroalkyl Substances in Runoff and Leaching from AFFF-Contaminated Soils: a Rainfall Simulation Study.

The mobilization and transport of per- and poly-fluoroalkyl substances (PFASs) via surface runoff (runoff) from aqueous film-forming foam (AFFF)-contaminated soils during rainfall, flooding, or irrigation has not been thoroughly evaluated, and the effectiveness of carbonaceous sorbents in limiting PFASs in runoff is similarly unquantified. Here, laboratory-scale rainfall simulations evaluate PFAS losses in runoff and in leaching to groundwater (leachate) from AFFF-contaminated soils varying in texture, PFAS composition and concentration, and remediation treatment. Leaching dominated PFAS losses in soils with a concentration of ∑PFAS = 0.2-2 mg/kg. However, with higher soil PFAS concentrations (∑PFAS = 31 mg/kg), leachate volumes were negligible and runoff dominated losses. The concentration and variety of PFASs were far greater in leachates regardless of the initial concentrations in soil. Losses of PFASs were dependent on the C-chain length for leachates and more on the initial concentration in soil for runoff. Suspended materials did not meaningfully contribute to runoff losses. While concentrations of most PFASs declined significantly after the first rainfall event, desorption and transport in both runoff and leachates persisted over several rainfall events. Finally, results showed that sorption to AC mostly occurred during, not prior to, rainfall events and that 1% w/w AC substantially reduced losses in runoff and leachates from all soils.

An Environmentally Relevant Mixture of Perfluorooctanesulfonic Acid and Perfluorohexanesulfonic Acid Does Not Conform to Additivity in Northern Leopard Frogs Exposed Through Metamorphosis.

Per- and polyfluoroalkyl substances (PFAS) are chemicals associated with adverse health effects. At aqueous film-forming foam sites, they occur as mixtures, with perfluorooctanesulfonic acid (PFOS) and perfluorohexanesulfonic acid (PFHxS) commonly co-occurring in the highest concentrations. Although PFOS and PFHxS toxicities have been studied, few studies have tested their potential interaction. Using Rana pipiens, the present study compared toxicities of a 1:1 PFOS:PFHxS mixture to PFOS and PFHxS individually with the prediction that responses would be additive. Gosner stage 25 (GS 25) tadpoles were exposed through metamorphosis (GS 46) to 0.5 and 1 ppb PFOS or PFHxS alone or to a mixture of 0.5 ppb PFOS and 0.5 ppb PFHxS. Tadpoles were weighed and measured (snout-vent length [SVL]) at day 31, metamorphic climax (GS 42), and GS 46. These values were used to calculate the scaled mass index (SMI), a measure of body condition. Body burdens were quantified on day 31 and at GS 46. The PFOS and PFHxS body burdens were elevated relative to controls at GS 46. No effects were observed on survival, SVL, or mass. Single PFAS effects included a 17% reduction in SMI at day 31 (0.5 ppb PFHxS) and a 1.1-day longer metamorphic period (1 ppb PFHxS) relative to controls. Mixture results deviated from additivity-SMIs were higher than expected on day 31 and lower than expected at GS 42. In addition, time to GS 42 in the PFAS mixture exceeded expected additivity by 12 days. Results from a chronic exposure to a 1:1 PFOS:PFHxS mixture resulted in changes in body condition and length of metamorphosis that deviated from additivity. More PFAS mixture toxicity studies conducted at relevant ratios and concentrations are needed. Environ Toxicol Chem 2022;41:3007-3016. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Fire-extinguishing performance and gas-phase pollution characteristics of different foam agents in extinguishing transformer oil pool fire

In this study, aqueous film-forming foam, fluoroprotein foam, and synthetic foam were applied to extinguish the transformer oil pool fires. The fire-extinguishing performance and burn-back resistance were investigated using a laboratory fire-extinguishing system. Moreover, the emission products were analyzed to evaluate the gas-phase pollution characteristics. Results show that aqueous film-forming foam presents the highest fire-extinguishing efficiency, while fluoroprotein foam has the best burn-back performance. Flue gas and gas chromatography–mass spectrometer analyses demonstrate that the use of fluoroprotein foam results in much higher CO emissions than other foams, and the pollutants are mainly from various hydrocarbons produced by incomplete combustion of transformer oil. Synthetic foam and aqueous film-forming foam lead to higher SO2 and NO emissions, and pollutants are mainly dominated by alcohols and ethers. Noteworthily, when using aqueous film-forming foam to extinguish oil pool fire, a persistent organic pollutant, perfluorooctanoic acid, is detected in the gas phase.

Removing per- and polyfluoroalkyl substances (PFAS) in water by foam fractionation

Treatment of large volumes of waters contaminated by per- and polyfluoroalkyl substances (PFAS) remains a challenge. This work presented a systematic study on PFAS removal by foam fractionation (FF). Experiments were conducted on both laboratory-spiked and environmental water samples containing PFASs. It is found that higher air flow, greater ionic strength, and addition of thickener boosted PFAS removal in the defoamed bottom solutions and intensified enrichment in the collected foam. FF treatments of a landfill leachate, a groundwater contaminated by aqueous film-forming foams, and a wastewater treatment plant effluent sample were evaluated. The removal reached above 70% for most monitored PFASs, except the ones of short alkyl chains. PFAS concentrations in the final collected foams were up to over 30 × than that in the original samples. Analysis using high-resolution mass spectrometry revealed enrichment of non-target PFASs by FF. The results of this study demonstrate great effectiveness of FF in removing most PFASs from waters, producing low-volume, highly concentrated solutions of PFASs in all tested environmental samples.

When Chemicals Go to the Dark Side

When Chemicals Go to the Dark Side

Biological and Chemical Transformation of the Six-Carbon Polyfluoroalkyl Substance N-Dimethyl Ammonio Propyl Perfluorohexane Sulfonamide (AmPr-FHxSA).

Sites impacted by aqueous film-forming foam (AFFF) contain co-contaminants that can stimulate biotransformation of polyfluoroalkyl substances. Here, we compare how microbial enrichments from AFFF-impacted soil amended with diethyl glycol monobutyl ether (found in AFFF), aromatic hydrocarbons (present in co-released fuels), acetate, and methane (substrates used or formed during bioremediation) impact the aerobic biotransformation of an AFFF-derived six-carbon electrochemical fluorination (ECF) precursor N-dimethyl ammonio propyl perfluorohexane sulfonamide (AmPr-FHxSA). We found that methane- and acetate-oxidizing cultures resulted in the highest yields of identifiable products (38 and 30%, respectively), including perfluorohexane sulfonamide (FHxSA) and perfluorohexane sulfonic acid (PFHxS). Using these data, we propose and detail a transformation pathway. Additionally, we examined chemical oxidation products of AmPr-FHxSA and FHxSA to provide insights on remediation strategies for AmPr-FHxSA. We demonstrate mineralization of these compounds using the sulfate radical and test their transformation during the total oxidizable precursor (TOP) assay. While perfluorohexanoic acid accounted for over 95% of the products formed, we demonstrate here for the first time two ECF-based precursors, AmPr-FHxSA and FHxSA, that produce PFHxS during the TOP assay. These findings have implications for monitoring poly- and perfluoroalkyl substances during site remediation and application of the TOP assay at sites impacted by ECF-based precursors.