Search Results (23)

In this study, the contamination of two drinking water catchments in Australia by per- and polyfluoroalkyl substances (PFAS) was investigated. PFASs in water and sediment were found at hazardous concentrations in waterways affected by transport accidents 24 and 33 years earlier. The exact cause(s) of the PFAS pollution remains unclear due to large data gaps. Both locations experienced burning fuel tankers suppressed using PFAS foam. PFAS contamination of a Blue Mountains water supply triggered the closure of two drinking water reservoirs 3–5 km downstream of the accident site. PFAS contamination of Central Coast’s Ourimbah Creek was concentrated in two floodplain wetlands adjacent to the accident site. The Ourimbah PFAS-affected wetlands are within 500 m of a drinking water groundwater bore field and 1.2 km from a raw water offtake used as part of Central Coast’s drinking water supply. The Blue Mountains contamination has impaired the Blue Mountains World Heritage Area, with perfluorooctane sulfonate (PFOS) exceeding aquatic ecosystem protection guidelines by 100 times. The mean PFOSs in stream water near the area of the Blue Mountains road accident were 2.16 µg L⁻¹ and 213.3 µg kg⁻¹ in stream sediment. This research demonstrates how spillages of small quantities of PFASs can cause major harm due to their extreme persistence, and their levels have exceedance of environmental and health guidelines for decades, with major adverse implications for drinking water supplies and conservation areas. Full article

Per- and Polyfluoroalkyl substances (PFASs) are commonly detected in airport stormwater runoff due to historical and ongoing use of aqueous film-forming foams (AFFFs). Conventional stormwater control measures (SCMs) are generally effective at removing PFASs associated with the particulate fraction, but may provide limited removal of dissolved-phase PFASs. Sorbent polishing beds represent a potential downstream treatment option; however, their applicability and performance for PFASs in stormwater have not been well studied. In this study, measured PFAS concentrations and runoff volumes from an AFFF-affected airport apron were combined with literature-derived sorption parameters to develop a screening-level framework for evaluating adsorber beds as polishing units for SCM effluent. Bed sizing was calculated using a representative empty bed contact time (EBCT) of 10 min and a design volume based on the 85th percentile storm event. Sorbent performance was evaluated using literature equilibrium partition coefficients (K_d) for activated carbons, ion exchange resins, and specialty materials to estimate operational lifetimes prior to regeneration or replacement. Model-based results indicated lifetimes ranging from approximately 7 years for activated carbon to more than 50 years for specialty materials, depending on PFAS chain length and affinity. Sensitivity analysis using quartile K_d ranges showed predicted lifetimes spanning orders of magnitude, emphasizing the screening-level nature of the estimates. This work links field monitoring data with conceptual adsorber design to support early-stage evaluation of sorbent polishing strategies for airport runoff management, supporting compliance under tightening discharge regulations. Full article

Fluorine-free foams (FFFs) have been introduced as alternatives to aqueous film-forming foams (AFFFs), which are based on per- and polyfluoroalkyl substances (PFASs). However, adoption of FFFs remains limited due to the lack of universal drop-in replacements and limited data on their health and environmental impacts. This study examined incentives and barriers to implementing FFFs in Fire Training Facilities (FTFs) to support the transition away from PFAS-based products. A survey was conducted from September 2022 to December 2023 across the U.S. and Canadian FTFs, including state-funded facilities, metropolitan fire departments, airports, military, and industrial brigades. Developed in partnership with fire service organizations, the survey assessed current foam use, motivations for transition, and associated challenges. Of all FTF training with Class B foams, 38% reported using FFF products. Primary incentives included environmental and health concerns, safety, and regulatory pressures. Key challenges were transition costs, training requirements, and uncertainties around disposal of foams. These findings highlight that while momentum toward FFF adoption is evident, ensuring products are genuinely PFAS-free and providing comprehensive training will be critical for effective, large-scale implementation. Fire training facilities can play a pivotal role in guiding this transition. Full article

Per- and polyfluoroalkyl substances (PFASs) have attracted global attention due to their persistence and biological toxicity, becoming critical emerging contaminants in river and lake environments worldwide. Building upon existing studies, this work aims to comprehensively understand the pollution patterns, environmental behaviors, and potential risks of PFASs in freshwater systems, thereby providing scientific evidence and technical support for precise pollution control, risk prevention, and the protection of aquatic ecosystems and human health. Based on publications from 2002 to 2025 indexed in the Web of Science (WoS), bibliometric analysis was used to explore the temporal evolution and research hotspots of PFASs, and to systematically review their input pathways, pollution characteristics, environmental behaviors, influencing factors, and ecological and health risks in river and lake environments. Results show that PFAS inputs originate from both direct and indirect pathways. Direct emissions mainly stem from industrial production, consumer product use, and waste disposal, while indirect emissions arise from precursor transformation, secondary releases from wastewater treatment plants (WWTPs), and long-range atmospheric transport (LRAT). Affected by source distribution, physicochemical properties, and environmental conditions, PFASs display pronounced spatial variability among environmental media. Their partitioning, degradation, and migration are jointly controlled by molecular properties, aquatic physicochemical conditions, and interactions with dissolved organic matter (DOM). Current risk assessments indicate that PFASs generally pose low risks in non-industrial areas, yet elevated ecological and health risks persist in industrial clusters and regions with intensive aqueous film-forming foam (AFFF) use. Quantitative evaluation of mixture toxicity and chronic low-dose exposure risks remains insufficient and warrants further investigation. This study reveals the complex, dynamic environmental behaviors of PFASs in river and lake systems. Considering the interactions between PFASs and coexisting components, future research should emphasize mechanisms, key influencing factors, and synergistic control strategies under multi-media co-pollution. Developing quantitative risk assessment frameworks capable of characterizing integrated mixture toxicity will provide a scientific basis for the precise identification and effective management of PFAS pollution in aquatic environments. Full article

To enhance the fire suppression performance of Class A foam, this study identifies sodium dodecyl sulfate (SDS) as the primary foaming agent and develops a high-efficiency foam system comprising primary and auxiliary foaming agents, wetting agents, and foam stabilizers. It interprets these macroscopic findings at the molecular level through molecular dynamics simulations. Sixteen formulations were designed using orthogonal experiments and evaluated in terms of surface tension, viscosity, wetting performance, and foam expansion ratio. The results demonstrated that the formulated systems exhibited superior foaming characteristics compared to conventional aqueous film-forming foam (AFFF), while other physicochemical properties were inferior. Two high-performing foam systems were further investigated using molecular dynamics simulations. Analysis of the spatial concentration distributions, diffusion coefficients, and the hydrogen-bonding networks of water molecules revealed 14.3% and 14.2% increases in the peak values of the radial distribution function (RDF) for the two systems modified with auxiliary foaming agents, respectively. The auxiliary foaming agents exhibited synergistic effects with SDS, enhancing its water activation capability. The incorporation of wetting agents reduced the water diffusion coefficients by 4.7% and 21.9%, indicating that sodium bis(2-ethylhexyl) succinate sulphonate (T) interferes less with the primary foaming agent than alcohol ethoxylate (AEO). The selected formulations also demonstrated 4.4% and 3.5% reductions in water hydrogen bonding compared to SDS-only solutions, indicating decreased molecular cohesion and improved water activation. By integrating physicochemical evaluation with molecular simulation, the optimized formulation was determined to be SDS (primary foaming agent), sodium fatty alcohol ether sulfate (auxiliary foaming agent), alcohol ethoxylate (wetting agent), lauryl hydroxysultaine (foam stabilizer), and ethylene glycol butyl ether (cosolvent). Full article

Poly- and perfluorinated alkyl substances (PFAS) are a group of chemicals that are widely used, prevalent in the environment, associated with several toxic effects, and often have long half-lives. Their persistence and relevant toxicity are the primary causes of environmental and human health concerns, and they are referred to as “forever chemicals” because of their persistence. Environmental accumulation caused by slow natural biodegradation and subsequent long environmental half-lives leads to bioaccumulation and makes PFAS more likely to be chronically toxic with potential transgenerational effects. Ultimately, it is this persistence that causes the greatest concern because PFAS-contaminated sites need costly remediation techniques, or else the contaminated areas will not be available for proper economic development because of social and economic suppression. Non-PFAS, alternative Aqueous Film Forming Foams (AFFF) that are considered environmentally friendly, are being heavily considered or currently used for fire suppression instead of PFAS-based products. The bioaccumulation and toxicity of alternative AFFF are just starting to be studied. The purpose of this review is to discuss the basic environmental and human health effects of PFAS and alternative AFFF that propel regulatory changes, increase clean-up costs, reduce economic development, and drive the development of novel alternatives. Full article

Per- and polyfluoroalkyl substances (PFAS) have been reported to contaminate soil as a result of improper management of waste, wastewater, landfill leachate, biosolids, and a large and indiscriminate use of aqueous film-forming foams (AFFF), posing potential risks to human health. However, their high chemical and thermal stability pose a great challenge for remediation. As a result, there is an increasing interest in identifying and optimizing very effective and sustainable technologies for PFAS removal. This review summarizes both traditional and innovative remediation strategies and technologies for PFAS-contaminated soils. Unlike existing literature, which primarily focuses on the effectiveness of PFAS remediation, this review critically discusses several techniques (based on PFAS immobilization, mobilization and extraction, and destruction) with a deep focus on their sustainability and scalability. PFAS destruction technologies demonstrate the highest removal efficiencies; however, thermal treatments face sustainability challenges due to high energy demands and potential formation of harmful by-products, while mechanical treatments have rarely been explored at full scale. PFAS immobilization techniques are less costly than destruction methods, but issues related to the regeneration/disposal of spent sorbents should be still addressed and more long-term studies conducted. PFAS mobilization techniques such as soil washing/flushing are hindered by the generation of PFAS-laden wastewater requiring further treatments, while phytoremediation is limited to small- or medium-scale experiments. Finally, bioremediation would be the cheapest and least impactful alternative, though its efficacy remains uncertain and demonstrated under simplified lab-scale conditions. Future research should prioritize pilot- and full-scale studies under realistic conditions, alongside comprehensive assessments of environmental impacts and economic feasibility. Full article

Long-chain per- and polyfluoroalkyl substances (PFASs) have been the standard active chemicals in aqueous film-forming foams (AFFFs or firefighting foams) since the mid-1960s. Some characteristics of PFASs are environmental persistence and bioaccumulation. Non-fluorinated firefighting foams are an alternative to potentially reducing the ecological/environmental impact of PFAS-based AFFF. We used northern bobwhite (NOBO, Colinus virginianus) to test the ecotoxicity of one candidate (non-fluorinated) foam. Fomtec Enviro USP is a fluorine-free commercial AFFF used primarily for extinguishing Class B hydrocarbon fuel fires. Following a photostimulation phase to initiate egg laying, breeding pairs were exposed for 60+ days to 0.01%, 0.1%, and 0.25% Fomtec in drinking water. The endpoints of the study included survival, growth, and reproductive output. Water consumption was evaluated and used to determine the average daily intake (ADI) based on Fomtec components: sodium dodecyl sulfate or SDS (0.05, 0.15, and 0.32 mg/kg/day for the 0.01%, 0.1%, and 0.25% Fomtec exposures, respectively) and diethylene glycol monobutyl ether or DGMBE (0.49, 6.54, and 18.37 mg/kg/day for the 0.01%, 0.1%, and 0.25% Fomtec exposures, respectively). Over the 60 days, control females laid an average of 59 ± 0.8 eggs compared to 28 ± 9 (0.01% Fomtec exposure), 51 ± 4 (0.1% Fomtec exposure), and 56 ± 2 (0.25% Fomtec exposure); the number of eggs produced per hen was affected by exposure to the lowest Fomtec concentration. Hatching success was not significantly different among treatment groups, and it was within normal reproduction parameters for quail. Our findings in this avian model help to fill data gaps for non-fluorinated foam products, many of which have little toxicological information. Full article

Aqueous film-forming foam (AFFF) is widely recognized for its excellent fire-extinguishing capabilities, yet the specific roles of its components remain insufficiently understood. AFFF typically consists of fluorocarbon and hydrocarbon surfactants, as well as organic solvents such as diethylene glycol butyl ether (DGBE), which can significantly influence foam performance. This study investigates the effects of surfactant mixtures and the DGBE additive on foam stability and fuel resistance at room temperature and ambient humidity. Static foam ignition experiments were conducted to assess fuel transport through foams using various hydrocarbon fuels, including n-octane, iso-octane, n-heptane, methylcyclohexane, methylcyclopentane, and a mixture of 25% trimethylbenzene with 75% n-heptane. Methylcyclopentane, with its higher vapor pressure and solubility, led to the shortest ignition times, indicating faster fuel transport. The addition of DGBE increased ignition times by a factor of 1.2 to 3.7 for individual surfactants, while the Capstone+Glucopon mixture improved ignition times by a factor of 2.4 to 5.5 compared to the individual surfactants. Further enhancement was observed with Capstone+Glucopon+DGBE, increasing ignition times by a factor of 3 to 7.3 compared to the individual surfactants. Additionally, combining DGBE with surfactant mixtures reduced fuel concentration in the bulk solution by over 60% compared to individual surfactants, significantly enhancing fuel resistance. Interface experiments showed that fuel presence, particularly methylcyclopentane and n-octane, altered the foam structure and accelerated drainage at the foam/fuel interface, impacting foam stability and fuel transport. These findings demonstrate that surfactant mixtures and DGBE-enhanced formulations substantially improve foam stability and fuel resistance. Full article

Per- and polyfluoroalkyl substances (PFAS) are diverse synthetic chemicals manufactured over seven decades. It is an aliphatic molecule with a basic hydrophobic structure of carbon and fluorine linked to a hydrophilic end group. Due to their physicochemical properties associated with the unique structure, PFAS has been used in a wide variety of applications including aqueous film-forming foams (AFFF), paper, carpets, non-stick cookware, etc. as they make products resistant to water, heat, and stains. These molecules have drawn great attention recently for their unique properties, high stability and low degradability, and so-called “Forever Chemicals”. PFAS has the strongest carbon-fluorine bond which makes them persistent in the environment. Hence it contaminates natural resources and endangers public health. This review discusses the discovery, development, and evolution of PFAS from the wonder chemical era to a nightmare chemical era, exposure and its impacts on human health and the environment, current remediation techniques, and future trends of PFAS molecules and related products. The primary objective of this review is to identify knowledge gaps on PFAS contamination, remediation methods, and possible PFAS alternatives. Full article

Tree swallow nest boxes were deployed at sites proximal to two putative aqueous film forming foam (AFFF) sources in the Duluth, MN area, as well as along the St. Louis River and a reference lake for comparative purposes in 2019, 2020 and 2021. The two AFFF sites were the current Duluth Air National Guard Base (ANG) and the Lake Superior College Emergency Response Training Center. Between 13 and 40 per- and polyfluoroalkyl substances (PFAS), depending on year, were detected and quantified in tree swallow egg, nestling carcasses, and stomach contents. Assessments were made of oxidative stress and ethoxyresorufin-O-dealkylase activity in liver tissue, thyroid hormone levels in plasma and thyroid glands, DNA damage in red blood cells, and two measures of immune response (haptoglobin-like activity and immunoglobulin) in plasma of the nestlings. Additionally, other contaminants, such as polychlorinated biphenyls, legacy organochlorine pesticides, and trace elements, were assessed at sites with no previous data. Total egg PFAS concentrations at the ANG site and north of that site were 30–40 times higher than at the reference lake, while nestling PFAS concentrations were 10–15 times higher. In contrast, the St. Louis River sites had slightly, but non-statistically significant, elevated egg and nestling PFAS concentrations relative to the reference lake (2–5 times higher). One PFAS, perfluorohexane sulfonate (PFHxS), was higher, as a proportion of total PFAS, at sites with a known AFFF source compared to the reference lake, as well as compared to sites along the St. Louis River with mainly urban and industrial sources of PFAS. The ratio of total carboxylates to total sulfonates also distinguished between PFAS sources. There were few to no differences in biomarker responses among sites, and no association with PFAS exposure. Full article

The mass loss mechanisms of an aqueous film-forming foam (AF foam), an AR/AFFF water-soluble film-forming foam extinguishing agent (AR foam), and a Class A foam extinguishing agent (A foam) at different levels of thermal radiation, thermal convection, and heat conduction intensity were studied. At a relatively low thermal radiation intensity, the liquid separation rate of the AF, AR, and A foams is related to the properties of the foam itself, such as viscosity and surface/interface tension, which are relatively independent of the external radiation heat flux of the foam. At low radiation intensity (15 kW/m² and 25 kW/m²), the liquid separation rate of the AF and A foams is relatively stable. When the heat flux intensity is 35 kW/m², the liquid separation rate of the AF and A foams increases notably, which may be mainly due to the rapid decrease in foam viscosity. And the mass loss behavior is dominated by liquid separation in the AF, AR, and A foams under the influence of thermal radiation and thermal convection. Under the same experimental conditions, the liquid separation rate of AF is the fastest. There is no significant difference in the evaporation rates of the three kinds of foam in the same heat conduction condition. In addition, the AR and A foams usually have a 25% longer liquid separation time (t) under thermal radiation and thermal convection, and the thermal stability is better than AF foam. The temperature reached by the AF foam layer under thermal convection was lower than that of the AR and A foams, and the time for the foam layer to reach the highest temperature under heat conduction was longer than that of the AR and A foams. Full article

A compressed-gas fire extinguishing experiment was carried out to analyze the impact of gas-liquid flow ratio, liquid flow rate and driving pressure on the fire suppression efficiency of aqueous film-forming foam (AFFF) in a diesel pool fire, and a possible fire-extinguishing mechanism was proposed. A fire suppression test showed that AFFF at a gas-liquid flow ratio of 16 between the range of 5 to 24 had the fastest fire-extinguishing temperature drop rate (16.67 °C/s), the shortest fire-extinguishing time, of 42 s, and the lowest foam solution consumption of 230 g, exhibiting the best fire suppression performance. Meanwhile, the fire suppression efficiency of AFFF improved with the augmentation of either liquid flow rate or system driving pressure. Based on fluid mechanics and combustion science, a foam fire-extinguishing mechanism was proposed to explain the influence of system parameters such as gas-liquid ratio, liquid flow rate and driving pressure on key combustion parameters such as temperature drop rate, evaporation rate and combustion rate, which can better illustrate the change in fire extinguishing performance. Full article

Per- and polyfluorinated alkyl substances (PFAS) are an environmentally persistent group of chemicals that can pose an imminent threat to human health through groundwater and surface water contamination. In this review, we evaluate the subsurface behavior of a variety of PFAS chemicals with a focus on aqueous film forming foam (AFFF) discharge sites. AFFF is the primary PFAS contamination risk at sites such as airports and military bases due to use as a fire extinguisher. Understanding the fate and transport of PFAS in the subsurface environment is a multifaceted issue. This review focuses on the role of adsorbent, adsorbate, and aqueous solution in the fate and transport of PFAS chemicals. Additionally, other hydrogeological, geochemical, ecological factors such as accumulation at air–water interfaces, subsurface heterogeneity, polyfluorinated PFAS degradation pathways, and plant interactions are discussed. This review also examines several case studies at AFFF discharge sites in order to examine if the findings are consistent with the broader PFAS literature. We present the most crucial future research directions and trends regarding PFAS and provide valuable insights into understanding PFAS fate and transport at AFFF discharge sites. We suggest a more comprehensive approach to PFAS research endeavors that accounts for the wide variety of environmental variables that have been shown to impact PFAS fate and transport. Full article

Storage tank fires can endanger society and the environment by generating intense heat radiation, rapidly spreading blazes, and cataclysmic explosions. Various types of foam and even two or more mixed foams are commonly used in storage tank fire disposal sites. This research aims to experimentally and analytically assess the efficacy of various and mixed forms of foam in putting out 120# gasoline pool fires. A series of foam fire extinguishing and re-ignition tests were conducted using a laboratory fire-extinguishing device that gently released low-expansion foam. In this work, a 2.4 m-diameter steel round tray was utilized to model the full-surface fire of an oilcan in a large oil depot base. The non-dimensional (T* = T_{Extinguishing}/T_{boiling point}) average temperature of 0.62–0.66 is used in this study to represent the fire extinguishing temperatures of 120# gasoline fuel. The power law is still followed during the spreading phase as the length of the foam spreads further with time. When combined, 6% aqueous film-forming foam solution and alcohol-resistant aqueous film-forming foam solution (AFFF + AFFF/AR) have the highest flow velocity of 0.0189 m s⁻¹. According to the results, synthesis foam solution combined with alcohol-resistant fluoroprotein foam (S + FP/AR) provided the greatest cooling effect, followed by S + S/AR (alcohol-resistant synthetic foam solution), AFFF/AR, S + AFFF, S/AR + AFFF, and finally S/AR + AFFF. According to the results, foam with an expansion ratio of 8.7:1 (FP (fluoroprotein foam solution) + AFFF/AR) has greater re-ignition resistance and burn-back protection. A referable tactic for choosing foam for liquid fire suppression is shown in this paper. The results suggested that FP and AFFF should be used for effective fire suppression in this hydrocarbon fuel fire rescue. Then, we can use synthetic foam and AR foams to provide continuous cooling and prevent the fire from re-igniting through efficient foam coverage. Full article