Aqueous Film-forming Foam Research Articles

Surface activity, foamability, and foam stability of binary mixed systems based on siloxane-based Gemini and hydrocarbon surfactants

Aiming to explore the potential of siloxane-based Gemini surfactants in the development of environmentally friendly foam extinguishing agent to address the pollution caused by traditional fluorinated ones. A crucial step is to study the performance of binary mixed systems of siloxane-based Gemini and hydrocarbon surfactants in terms of surface activity, foamability, and foam stability. In this study, binary mixed systems of two types of siloxane-based Gemini surfactants and one siloxane surfactant with four different hydrocarbon surfactants are prepared. Parameters such as surface tension, foam height, drainage time, and coarsening rate are tested. The results show that the siloxane-based Gemini surfactant HY-4000 with double silane chains could effectively reduce the surface tension of hydrocarbon surfactants. In addition, the two types of Gemini surfactants performed better in enhancing the foamability of hydrocarbon surfactants. The siloxane OFX0193 even inhibits the foaming of cationic hydrocarbon surfactant CATC. Besides the HY-4000/APG0180 mixed system, the binary mixed systems of three silicone surfactants with AOS and APG0180 exhibit better foam stability, particularly the systems containing TEGO4100. For the coarsening process of foam bubbles, we develop a predictive model based on previous studies, where the relationship between bubble area and time follows a power function law. The findings of this study could provide guidance for the development of green foam extinguishing agent with siloxane-based Gemini and hydrocarbon surfactants as core components.

Linking exposure to per- and polyfluoroalkyl substances (PFAS) in house dust and biomonitoring data in eight impacted communities

Per- and polyfluoroalkyl substances (PFAS) are widely used in industry and have been linked to various adverse health effects. Communities adjacent to sites where PFAS are manufactured, stored, or used may be at elevated risk. In these impacted communities, significant exposure often occurs through contaminated drinking water, yet less is known about the role of other pathways such as residential exposure through house dust. We analyzed a paired serum and house dust dataset from the Agency for Toxic Substances and Disease Registry’s PFAS Exposure Assessments, which sampled eight United States communities with a history of drinking water contamination due to aqueous film forming foam (AFFF) use at nearby military bases. We found that serum PFAS levels of residents were significantly positively associated with the dust PFAS levels in their homes, for three of seven PFAS analyzed, when accounting for site and participant age. We also found that increased dust PFAS levels were associated with a shift in the relative abundance of PFAS in serum towards those chemicals not strongly linked to AFFF contamination, which may suggest household sources. Additionally, we analyzed participant responses to exposure questionnaires to identify factors associated with dust PFAS levels. Dust PFAS levels for some analytes were significantly elevated in households where participants were older and had lived at the home longer, cleaned less frequently, used stain resistant products, and had carpeted living rooms. Our results suggest that residential exposure to PFAS via dust or other indoor pathways may contribute to overall exposure and body burden, even in communities impacted by AFFF contamination of drinking water, and the magnitude of this exposure may also be influenced by demographic, behavioral, and housing factors.

EXPIRED FOAM EXTINGUISHING AGENTS AND EVALUATION OF THEIR SUITABILITY FOR FURTHER USE

Foam extinguishing agents are one of the most commonly used and effective means usedduring rescue and firefighting operations. However, their applicability depends on a numberof parameters, which are defined in relevant standards and guidelines. They include substancesthat are characterised by greater or lesser toxicity, such as fluoroorganic compounds, so properhandling of these materials is one of the priorities for their management. The analysis involved3 foam extinguishing agents of different compositions (types FP, AFFF, AR) after the lapse of theirdeclared useful life by the manufacturers. These agents were tested for selected parameters vitalfor proper firefighting operations, i.e. the expansion ratio and condensation times of the agentssubjected to temperature conditioning and the extinguishing efficiency on a small scale.

Large-Scale Fire Tests of Battery Electric Vehicle (BEV): Slovak Case Study

Due to the increasing number of battery electric vehicles (BEV) on the roads and the number of BEV accidents with the occurrence of a fire, full-scale fire tests of BEVs were carried out. For initiation, the BEVs were mechanically damaged, forming a gap with a size of 15 cm × 15 cm. The external heat source was a 300 kW propane burner with a maximum power of 54.0 kW and a length of 54 cm. The flame of the propane–butane fuel mixed in air at a temperature of 1970 °C was inserted directly into the battery pack. The increase in the temperature was monitored as a function of time through thermocouples at selected locations of the BEV until the point of initiation. Thermocouples were placed 10, 30, and 50 cm from the place of BEV surface. Accordingly, to obtain the temperature–time curves from the experiment measurement, critical temperatures were subsequently evaluated. The fire tests on BEVs can be described according to the individual phases of the fire. The external heat source started the initiation process at the 25 min time mark. Consequently, the phase of a developed fire with a dynamic course started. A sharp rise in temperature occurred. Within two minutes, the temperature rose to 1056.9 °C. After the initiation source was removed, there was decline in temperature and re-ignition to the stage of a fully developed fire. Thermocouples recorded temperatures in the range of 900 °C. The resulting dynamic process of a BEV fire with a sharp increase in temperature is a problem for the implementation of firefighting works and the liquidation of traffic accidents. Furthermore, foam extinguishing was part of the experiments. In both cases after the foam application, the temperature on the thermocouple T1 (distance was 10 cm from the surface of the BEV) dropped from 486.1 °C to 76 °C after 10 s of application.

Sulfonamide Per- and Polyfluoroalkyl Substances Can Impact Microorganisms Used in Aromatic Hydrocarbon and Trichloroethene Bioremediation.

Per- and polyfluoroalkyl substances (PFASs) from aqueous film forming foams (AFFFs) can hinder bioremediation of co-contaminants such as trichloroethene (TCE) and benzene, toluene, ethylbenzene, and xylene (BTEX). Anaerobic dechlorination can require bioaugmentation of Dehalococcoides, and for BTEX, oxygen is often sparged to stimulate in situ aerobic biodegradation. We tested PFAS inhibition to TCE and BTEX bioremediation by exposing an anaerobic TCE-dechlorinating coculture, an aerobic BTEX-degrading enrichment culture, and an anaerobic toluene-degrading enrichment culture to n-dimethyl perfluorohexane sulfonamido amine (AmPr-FHxSA), perfluorohexane sulfonamide (FHxSA), perfluorohexanesulfonic acid (PFHxS), or nonfluorinated surfactant sodium dodecyl sulfate (SDS). The anaerobic TCE-dechlorinating coculture was resistant to individual PFAS exposures but was inhibited by >1000× diluted AFFF. FHxSA and AmPr-FHxSA inhibited the aerobic BTEX-degrading enrichment. The anaerobic toluene-degrading enrichment was not inhibited by AFFF or individual PFASs. Increases in amino acids in the anaerobic TCE-dechlorinating coculture compared to the control indicated stress response, whereas the BTEX culture exhibited lower concentrations of all amino acids upon exposure to most surfactants (both fluorinated and nonfluorinated) compared to the control. These data suggest the main mechanisms of microbial toxicity are related to interactions with cell membrane synthesis as well as protein stress signaling.

Environmentally friendly fluorine-free fire extinguishing agent based on the synergistic effect of silicone, hydrocarbon surfactants and foam stabilizers

The environmentally friendly fluorine-free fire extinguishing agent based on the silicone surfactant was developed in order to solve the environmental hazards and bio-accumulative of traditional aqueous film-forming foam (AFFF). The carboxyl modified polyether polysiloxane surfactant (CMPS) was an efficient alternative to fluorocarbon surfactant, which was firstly synthesized via the esterification reaction using hydroxyl-containing polyether modified polysiloxane (HPMS) and maleic anhydride (MA) as raw materials. Then the surface activity, foam properties, micellar morphology of the CMPS and four hydrocarbon surfactants, as well as their mixture are evaluated by surface tension, Ross-Miles and cryo-transmission electron microscopy (Cryo-TEM). And the suitable key amount of CMPS and hydrocarbon surfactants added to the extinguishing agent were optimized by orthogonal tests. Moreover, the effect of foam stabilizer on the surface activity, foam property and fire extinguishing performance of fire extinguishing agent are also analyzed. Consequently, a new environmentally friendly fluorine-free fire extinguishing agent was prepared and the surface tension, the interfacial tension, foam properties, bubble morphology, spreading behavior and fire extinguishing mechanism were systematically characterized. The Cryo-TEM results illustrate that the intense interaction among silicone and hydrocarbon molecules exists in the the mixture of CMPS and hydrocarbon surfactants, which is produced through the change of micellar morphology, i.e. microscopic larger spheroidal micelles of CMPS transited to smaller spheroidal micelles and wormlike micelles in the mixed system. The surface tension of synthesized foam extinguishing agent is 22.3 mN/m and the spread coefficient is 0.9 mN/m, which has excellent surface activity and spreading property. The prepared foam extinguishing agent exhibits superior fire-fighting property, which can be attributed to the high surface activity, good foam property and superior foam stability. The research results of this paper lay a theoretical foundation for the research and development of efficient environmentally friendly foam extinguishing agent.

Anaerobic biodegradation of perfluorooctane sulfonate (PFOS) and microbial community composition in soil amended with a dechlorinating culture and chlorinated solvents

Perfluorooctane sulfonate (PFOS), one of the most frequently detected per- and polyfluoroalkyl substances (PFAS) occurring in soil, surface water, and groundwater near sites contaminated with aqueous film-forming foam (AFFF), has proven to be recalcitrant to many destructive remedies, including chemical oxidation. We investigated the potential to utilize microbially mediated reduction (bioreduction) to degrade PFOS and other PFAS through addition of a known dehalogenating culture, WBC-2, to soil obtained from an AFFF-contaminated site. A substantial decrease in total mass of PFOS (soil and water) was observed in microcosms amended with WBC-2 and chlorinated volatile organic compound (cVOC) co-contaminants — 46.4 ± 11.0 % removal of PFOS over the 45-day experiment. In contrast, perfluorooctanoate (PFOA) and 6:2 fluorotelomer sulfonate (6:2 FTS) concentrations did not decrease in the same microcosms. The low or non-detectable concentrations of potential metabolites in full PFAS analyses, including after application of the total oxidizable precursor assay, indicated that defluorination occurred to non-fluorinated compounds or ultrashort-chain PFAS. Nevertheless, additional research on the metabolites and degradation pathways is needed. Population abundances of known dehalorespirers did not change with PFOS removal during the experiment, making their association with PFOS removal unclear. An increased abundance of sulfate reducers in the genus Desulfosporosinus (Firmicutes) and Sulfurospirillum (Campilobacterota) was observed with PFOS removal, most likely linked to initiation of biodegradation by desulfonation. These results have important implications for development of in situ bioremediation methods for PFAS and advancing knowledge of natural attenuation processes.

Near-complete destruction of PFAS in aqueous film-forming foam by integrated photo-electrochemical processes

Near-complete destruction of PFAS in aqueous film-forming foam by integrated photo-electrochemical processes

Understanding the Impact of Fuel on Surfactant Microstructure of Firefighting Foam

Aqueous film-forming foam is being phased out due to the environmental impacts of fluorinated surfactants contained in the firefighting foams. To develop an environmentally friendly firefighting foam, it is important to understand the factors controlling the firefighting performance of surfactants. Fuel transport through foam has been considered as a dominant mechanism for foam collapse. Therefore, the impact of fuels (heptane, octane and trimethylbenzene (TMB)) on surfactant microstructure was studied for three different types of surfactants (Capstone, Glucopon, and siloxane) that have applications in firefighting foam. Multiple techniques were used to identify the microstructure and interfacial properties of surfactants with and without exposure to liquid fuel. The ignition time of fuel vapor through foam and solubility of fuel through liquid surfactant solution were measured as well. This work shows fuel solubility has an impact on the surfactant microstructure and interfacial properties. In addition, fuel solubility and vapor pressure affect the ignition time of fuel vapors.

The Effect of Gestational PFOS Exposure on Metabolism in the F344 Rat

Perfluorooctanesulfonate (or PFOS) is a type of PFOA known as (per-and poly-fluorinated alkylated substance) which is a manufactured compound chemical made of a strong carbon-fluorine and sulfonic acid. Due to its hydrophobic and lipophobic properties, industries use it in food wrappers, fire-fighting foam, sweat-proof clothing, and household cleaning products. PFOS exposure is an endocrine disruptor that may induce Metabolic Syndrome (MetS), an association of disorders that increases the risk of significant health issues like heart disease, diabetes, and stroke. Gestational and lactational exposure to Perfluorooctanesulfonate (PFOS) in F344/Stm rats was hypothesized to induce metabolic dysfunction in both female and male offspring. Pregnant F344 rats were given a control diet or diet containing 15mg/kg or 30mg/kg of PFOS; measures of body weight and body composition through nuclear magnetic resonance (NMR) were performed, and tissue was measured at the euthanasia of the dams. Both female and male offspring exposed during pregnancy and lactation were subject to the same protocol with tissue collection at three ages. On both low and high doses of PFOS, the pregnant females showed a decreased body weight gain compared to the control group; males and females also showed decreased body weight at three weeks of age when weaned from the exposed female. At 16 weeks of age, the same patterns were not revealed. The results from NMR suggested a 21% decrease in fat percentage and a 23% decrease in fat for the high exposure in the dams. The offspring at three weeks old showed a reduction in fat mass, fat mass %, and fat-free % in both high and low-dose groups compared to the control group; on the other hand, at 16 weeks old, this trend is not shown. The results suggest that PFOS had a short-term metabolic effect on the offspring at the younger; however, at the adult age, they seem to recover their initial phenotypes. For future studies, it suggested the focus on underlying mechanisms responsible for the rodent's recovery. ASPIRE Program (R25HL168782) Medical College of Wisconsin. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

PFAS Porewater concentrations in unsaturated soil: Field and laboratory comparisons inform on PFAS accumulation at air-water interfaces

Poly- and perfluoroalkyl substance (PFAS) leaching from unsaturated soils impacted with aqueous film-forming foams (AFFFs) is an environmental challenge that remains difficult to measure and predict. Complicating measurements and predictions of this process is a lack of understanding between the PFAS concentrations measured in a collected environmental unsaturated soil sample, and the PFAS concentrations measured in the corresponding porewater using field-deployed lysimeters. The applicability of bench-scale batch testing to assess this relationship also remains uncertain. In this study, field-deployed porous cup suction lysimeters were used to measure PFAS porewater concentrations in unsaturated soils at 5 AFFF-impacted sites. Field-measured PFAS porewater concentrations were compared to those measured in porewater extracted in the laboratory from collected unsaturated soil cores, and from PFAS concentrations measured in the laboratory using batch soil slurries. Results showed that, despite several years since the last AFFF release at most of the test sites, precursors were abundant in 3 out of the 5 sites. Comparison of field lysimeter results to laboratory testing suggested that the local equilibrium assumption was valid for at least 3 of the sites and conditions of this study. Surprisingly, PFAS accumulation at the air-water interface was orders of magnitude less than expected at two of the test sites, suggesting potential gaps in the understanding of PFAS accumulation at the air-water interface at AFFF-impacted sites. Finally, results herein suggest that bench-scale testing on unsaturated soils can in some cases be used to inform on PFAS in situ porewater concentrations.

Perfluoroalkyl/Polyfluoroalkyl Substances: Links to Cardiovascular Disease Risk.

Conservative estimates by the World Health Organization suggest that at least a quarter of global cardiovascular diseases are attributable to environmental exposures. Associations between air pollution and cardiovascular risk have garnered the most headlines and are strong, but less attention has been paid to other omnipresent toxicants in our ecosystem. Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are man-made chemicals that are extensively used in industrial and consumer products worldwide and in aqueous film-forming foam utilized in firefighting. As such, our exposure to PFAS is essentially ubiquitous. Given the long half-lives of these degradation-resistant chemicals, virtually, all people are carrying a body burden of PFAS. Health concerns related to PFAS are growing such that the National Academies of Sciences, Engineering and Medicine has recommended standards for clinical follow-up of individuals with high PFAS blood levels, including prioritizing screening for dyslipidemia. The link between PFAS and dyslipidemia has been extensively investigated, and evidence for associations is compelling. However, dyslipidemia is not the only cardiovascular risk factor with which PFAS is associated. Here, we review the epidemiological evidence for links between PFAS of concern identified by the National Academies of Sciences, Engineering and Medicine and risk factors for cardiovascular disease, including overweight/obesity, glucose intolerance, hypertension, dyslipidemia, and hyperuricemia. Moreover, we review the potential connections of PFAS with vascular disease and atherosclerosis. While observational data support associations between the National Academies of Sciences, Engineering and Medicine PFAS and selected cardiac risk factors, additional research is needed to establish causation and better understand how exposure to PFAS leads to the development of these conditions.

Design of fluorine-free foam extinguishing agent with high surface activity, foam stability and pool fire suppression by optimization of surfactant composition and foam system

To meet the environmental requirement of foam extinguishing agent, a novel fluorine-free surfactant named amino-terminated polyether modified silicone (ATPMS) was successfully synthesized, and then in combination with hydrocarbon surfactant prepared fluorine-free foam extinguishing agent. The study carefully investigated surface tension, foamability, foam stability and fire extinguishing performance of fluorine-free foam extinguishing agent. The results indicate that ATPMS has a low surface tension of 21.17 mN/m, which combined with hydrocarbon surfactant at the mass concentration ratio of 1:1 imparts high surface activity. The sodium lauryl ether sulfate (AES)/ATPMS system owes the optimal comprehensive performance with an initial foam height value of 85.8 mm, a surface tension value of 24.76 mN/m and a foam stability value (the ratio of foam height between initial foam and five-minute foam) of 64.0 % at critical micelle concentration (CMC), respectively. Fire suppression test shows that the obtained fluorine-free foam extinguishing agent is effective in fighting diesel pool fires. The firefighting efficiency of foam agent links to the mixing chamber structure of compressed air foam fire extinguishing system (CAFS). When the mixing chamber of CAFS has a recurrent segment length of 50 mm and the filled particle size of 10 mm, the firefighting efficiency of fluorine-free foam extinguishing agent is optimal with a fire extinguishing time of 33 s and a temperature drop rate of 6.49 °C/s.

Assessing the suitability of leachability-based screening levels for per- and polyfluoroalkyl substances (PFAS) risk assessment

In recent years, soil screening levels have been adopted by regulatory agencies for certain per- and polyfluoroalkyl substances (PFAS) to assess the risk of groundwater contamination through leaching. These soil screening levels, determined using an established equilibrium-based partitioning equation, have high variability among regulatory groups largely attributed to the diverse reported partitioning coefficients in the literature. This variability between reported partitioning coefficients, and subsequently soil screening levels, is due to the complex leaching behavior of PFAS not being predicted well by the standard equilibrium-based model. This has led one regulatory group to require batch leaching to assess risk rather than setting default soil screening levels based on partitioning equations. In this work, we conducted leaching experiments on five field-sampled soils impacted by aqueous film-forming foams (AFFF), following Leaching Environmental Assessment Framework (LEAF) Method 1316 and compared the results to expected leaching utilizing an equilibrium-based partitioning equation commonly employed by regulatory agencies to establish soil screening levels. Our analysis found among the six PFAS detected in the soils, which have regulatory leaching thresholds established, the partitioning values assumed by the U.S. EPA exhibited the highest accuracy in predicting leachate concentrations. These partitioning values predicted actual leaching within a ± 20 % margin of error for approximately 50 % of sample points, highlighting limitations in relying solely on equilibrium-based partitioning values as predictors of leaching behavior. This discrepancy between predicted and actual leaching has implications for site managers and regulatory entities overseeing PFAS-contaminated sites, suggesting that soil screening level determinations for PFAS might need to be revised to account for the unique transport characteristics of PFAS.

The Influence of the Heat Transfer Mode on the Stability of Foam Extinguishing Agents

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.

Mechanochemical degradation of per- and polyfluoroalkyl substances in soil using an industrial-scale horizontal ball mill with comparisons of key operational metrics

Horizontal ball mills (HBMs) have been proven capable of remediating per- and polyfluoroalkyl substances (PFAS) in soil. Industrial-sized HBMs, which could easily be transported to impacted locations for on-site, ex-situ remediation, are readily available. This study examined PFAS degradation using an industrial-scale, 267 L cylinder HBM. This is the typical scale used in the industry before field application. Near-complete destruction of 6:2 fluorotelomer sulfonate (6:2 FTS), as well as the non-target PFAS in a modern fluorotelomer-based aqueous film forming foam (AFFF), was achieved when spiked onto nepheline syenite sand (NSS) and using potassium hydroxide (KOH) as a co-milling reagent. Perfluorooctanesulfonate (PFOS) showed much better and more consistent results with scale-up regardless of KOH. Perfluorooctanoate (PFOA) was examined for the first time using a HBM and behaved similarly to PFOS. Highly challenging field soils from a former firefighting training area (FFTA) were purposefully used to test the limits of the HBM. To quantify the effectiveness, free fluoride analysis was used; changes between unmilled and milled soil were measured up to 7.8 mg/kg, which is the equivalent of 12 mg/kg PFOS. Notably, this does not factor in insoluble fluoride complexes that may form in milled soils, so the actual amount of PFAS destroyed may be higher. Soil health, evaluated through the assessment of key microbial and associated plant health parameters, was not significantly affected as a result of milling, although it was characterized as poor to begin with. Leachability reached 100 % in milled soil with KOH, but already ranged from 81 to 96 % in unmilled soil. A limited assessment of the hazards associated with the inhalation of PFAS-impacted dust from ball-milling, as well as the cross-contamination potential to the environment, showed that the risk was low in both cases; however, precautions should always be taken.

Spatial distribution, compositional characteristics, and source apportionment of legacy and novel per- and polyfluoroalkyl substances in farmland soil: A nationwide study in mainland China

China, as one of the largest global producers and consumers of per- and poly-fluoroalkyl substances (PFASs), faces concerning levels of PFAS pollution in soil. However, knowledge of their occurrence in agricultural soils of China on the national scale remains unknown. Herein, the first nationwide survey was done by collecting 352 soil samples from 31 provinces in mainland China. The results indicated that the Σ24PFASs concentrations were 74.3 - 24880.0 pg/g, with mean concentrations of PFASs in decreasing order of legacy PFASs > emerging PFASs > PFAS precursors (640.2 pg/g, 340.7 pg/g, and 154.9 pg/g, respectively). The concentrations in coastal eastern China were distinctly higher than those in inland regions. Tianjin was the most severely PFASs-contaminated province because of rapid urban industrialization. This study further compared the PFAS content in monoculture and multiple cropping farmland soils, finding the concentrations of PFASs were high in soils planted with vegetable and fruit monocultures. Moreover, a positive matrix factorization (PMF) model was employed to identify different sources of PFASs. Fluoropolymer industries and aqueous film-forming foams were the primary contributors. The contributions from different emission sources varied across the seven geographical regions. This study provides new baseline data for prevention and control policies for reducing pollution.

Influence of typical liquid fuels on foam properties of critical components of environmentally friendly aqueous film-forming foams

In this study, the influence mechanism of typical fuels (oils) on the foam properties of mixture of hydrocarbon and fluorocarbon surfactants was investigated. A mixed solution was prepared based on a nonionic hydrocarbon surfactant (APG-0810) and a zwitterionic C6 fluorocarbon surfactant (short-chain). The effect of different oils (heptane, kerosene, diesel, and transformer oil) on the physical property parameters, foamability, oil resistivity of foam and single vertical liquid film of the mixture are systematically investigated. Results indicate that the viscosity of mixture increases, but the conductivity, surface activity, and initial foam height decreases with addition of the four oils. The drainage and volume decay of the foam are accelerated by the presence of oils. In addition, the presence of oils accelerates liquid film thinning through affecting drainage, especially for the oil with higher density, water solubility, and volatility. The four oils showed different effect on foam properties due to the difference in nature and emulsification of them. Among them, the foam properties under the action of heptane is the best, and the oil resistivity of foams is the best. This study can provide theoretical guidance for oil resistivity of hydrocarbon and fluorocarbon surfactant stabilized foams.

PFAS Contamination in Europe: Generating Knowledge and Mapping Known and Likely Contamination with "Expert-Reviewed" Journalism.

While the extent of environmental contamination by per- and polyfluoroalkyl substances (PFAS) has mobilized considerable efforts around the globe in recent years, publicly available data on PFAS in Europe were very limited. In an unprecedented experiment of "expert-reviewed journalism" involving 29 journalists and seven scientific advisers, a cross-border collaborative project, the "Forever Pollution Project" (FPP), drew on both scientific methods and investigative journalism techniques such as open-source intelligence (OSINT) and freedom of information (FOI) requests to map contamination across Europe, making public data that previously had existed as "unseen science". The FPP identified 22,934 known contamination sites, including 20 PFAS manufacturing facilities, and 21,426 "presumptive contamination sites", including 13,745 sites presumably contaminated with fluorinated aqueous film-forming foam (AFFF) discharge, 2911 industrial facilities, and 4752 sites related to PFAS-containing waste. Additionally, the FPP identified 231 "known PFAS users", a new category for sites with an intermediate level of evidence of PFAS use and considered likely to be contamination sources. However, the true extent of contamination in Europe remains significantly underestimated due to a lack of comprehensive geolocation, sampling, and publicly available data. This model of knowledge production and dissemination offers lessons for researchers, policymakers, and journalists about cross-field collaborations and data transparency.

Molecular Dynamics Simulations of the Short-Chain Fluorocarbon Surfactant PFHXA and the Anionic Surfactant SDS at the Air/Water Interface.

The research and development of alternatives to long-chain fluorocarbon surfactants are desperately needed because they are extremely toxic, difficult to break down, seriously harm the environment, and limit the use of conventional aqueous film-forming foam fire extinguishing agents. In this study, mixed surfactant systems containing the short-chain fluorocarbon surfactant perfluorohexanoic acid (PFHXA) and the hydrocarbon surfactant sodium dodecyl sulfate (SDS) were investigated by molecular dynamics simulation to investigate the microscopic properties at the air/water interface at different molar ratios. Some representative parameters, such as surface tension, degree of order, density distribution, radial distribution function, number of hydrogen bonds, and solvent-accessible surface area, were calculated. Molecular dynamics simulations show that compared with a single type of surfactant, mixtures of surfactants provide superior performance in improving the interfacial properties of the gas-liquid interface. A dense monolayer film is formed by the strong synergistic impact of the two surfactants. Compared to the pure SDS system, the addition of PFHXA caused SDS to be more vertically oriented at the air/water interface with a reduced tilt angle, and a more ordered structure of the mixed surfactants was observed. Hydrogen bonding between SDS headgroups and water molecules is enhanced with the increasing PFHXA. The surface activity is arranged in the following order: PFHXA/SDS = 1:1 > PFHXA/SDS = 3:1 > PFHXA/SDS = 1:3. These results indicate that a degree of synergistic relationship exists between PFHXA and SDS at the air/water interface.