New PFASs Identified in AFFF Impacted Groundwater by Passive Sampling and Nontarget Analysis.

Monitoring contamination from per- and polyfluoroalkyl substances (PFASs) in water systems impacted by aqueous film-forming foams (AFFFs) typically addresses a few known PFAS groups. Given the diversity of PFASs present in AFFFs, current analytical approaches do not comprehensively address the range of PFASs present in these systems. A suspect-screening and nontarget analysis (NTA) approach was developed and applied to identify novel PFASs in groundwater samples contaminated from historic AFFF use. A total of 88 PFASs were identified in both passive samplers and grab samples, and these were dominated by sulfonate derivatives and sulfonamide-derived precursors. Several ultrashort-chain (USC) PFASs (≤C3) were detected, 11 reported for the first time in Australian groundwater. Several transformation products were identified, including perfluoroalkane sulfonamides (FASAs) and perfluoroalkane sulfinates (PFASis). Two new PFASs were reported (((perfluorohexyl)sulfonyl)sulfamic acid; m/z 477.9068 and (E)-1,1,2,2,3,3,4,5,6,7,8,8,8-tridecafluorooct-6-ene-1-sulfonic acid; m/z 424.9482). This study highlights that several PFASs are overlooked using standard target analysis, and therefore, the potential risk from all PFASs present is likely to be underestimated.

Sorption affinity and mechanisms of per-and polyfluoroalkyl substances (PFASs) with commercial sorbents: Implications for passive sampling.

Effective monitoring tools, including passive samplers, are essential for the wide range of per- and polyfluoroalkyl substances (PFASs) in aquatic matrices. However, knowledge of the extent and mechanisms of PFASs sorption with sorbents in a passive sampling context is limited. To address this, sorption behavior of 45 anionic, neutral and zwitterionic PFASs ranging in perfluorocarbon chain length (C3-C16) and functional groups with 11 different commercial sorbents (cross-linked ß-cyclodextrin polymers, activated carbon, anion exchange (AE), cation exchange, hydrophilic-lipophilic balanced (HLB) and non-polar) was investigated. A broad range of equilibrium sorbent-MilliQ water (MQ) distribution coefficients (Kd) were observed (10-1.95 to 108.30 mL g-1). Similar sorbent types (e.g., various AE and HLB sorbents) exhibited very different sorption behavior, likely due to their different polymeric structures and relative importance of sorbate/sorbent interactions other than coulombic interactions. HLB and AE with hydroxyl functionalities are most effective for sampling of the full suite of PFASs. Reduced sorptive affinity was observed in the presence of matrix co-constituents in wastewater influent for most PFASs. HLB had the smallest reduction in log Kd in wastewater suggesting that these sorbents are appropriate for applications in complex matrices. Sufficient sorbent capacity was observed for linear uptake of many target analytes which facilitates passive sampling.

Quantification of the variability and penetration of per- and poly-fluoroalkyl substances through a concrete pad.

Historical use of aqueous film forming foams (AFFF) containing per- and poly-fluoroalkyl substances (PFAS) for fire-fighting activities has contributed to widespread contamination of infrastructure which can represent an ongoing source of PFAS to the surrounding environment. A concrete fire training pad with historical use of Ansulite and Lightwater AFFF formulations had PFAS concentrations measured to quantify spatial variability of PFAS within the pad. Surface chips and whole cores of concrete through to the underlying aggregate base were collected over the 24 × 9 m concrete pad and depth profiles of PFAS concentrations in nine cores were analysed. PFOS and PFHxS dominated the PFAS for surface samples, along the depth profile of cores and in the underlying plastic and aggregate material, with substantial variability in the concentrations of PFAS in the samples. Although there was variability of individual PFAS along the depth profile, higher surface concentrations of PFAS generally followed the designed movement of water across the pad. Total oxidisable precursor (TOP) assessments of one core indicated additional PFAS were present along the entire length of the core. This study highlights concentrations of PFAS (up to low µg/kg) from historical use of AFFF can occur throughout concrete, with the variable concentrations throughout the profile.

Stabilisation of PFAS in soils: Long-term effectiveness of carbon-based soil amendments.

Immobilisation/stabilisation is one of the most developed and studied approaches for treating soils contaminated with per- and poly-fluoroalkyl substances (PFAS). However, its application has been inhibited by insufficient understanding of the effectiveness of added soil sorbents over time. Herein, we present results on the effectiveness of select carbon-based sorbents, over 4 years (longevity) and multiple laboratory leaching conditions (durability). Standard batch leaching tests simulating aggressive, worst-case scenario conditions for leaching (i.e., shaking for 24-48 h at high liquid/solid ratios) were employed to test longevity and durability of stabilisation in clay-loam and sandy-loam soils historically contaminated with PFAS (2 and 14 mg/kg ∑28 PFAS). The different sorbents, which were applied at 1-6% (w/w), reduced leaching of PFAS from the soils to varying degrees. Among the 5 sorbents tested, initial assessments completed 1 week after treatment revealed that 2 powdered activated carbon (PAC) sorbents and 1 biochar were able to reduce leaching of PFAS in the soil by at least 95%. Four years after treatment, the performance of the PAC sorbents did not significantly change, whilst colloidal AC improved and was able to reduce leaching of PFAS by at least 94%. The AC-treated soils also appeared to be durable and achieved at least 95% reduction in PFAS leaching under repetitive leaching events (5 times extraction) and with minimal effect of pH (pH 4-10.5). In contrast, the biochars were affected by aging and were at least 22% less effective in reducing PFAS leaching across a range of leaching conditions. Sorbent performance was generally consistent with the sorbent's physical and chemical characteristics. Overall, the AC sorbents used in this study appeared to be better than the biochars in stabilising PFAS in the long term.

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.

Trial of a novel experimental design to test depuration of PFASs from the edible tissues of Giant Mud Crab following exposure under natural conditions in the wild.

Poly and perfluorinated alkyl substances (PFASs) are persistent organic pollutants (POPs) that are highly resistant to environmental degradation, and have been detected in a broad range of terrestrial and aquatic species. Portunid crabs have been shown to accumulate comparatively high concentrations of PFASs, but previous work examining depuration in crabs was inconclusive. Here, we trialled a novel experimental design to study depuration of PFASs from edible tissues of portunid crabs, using paired claw samples, and trial this design with Giant Mud Crab Scylla serrata exposed to the contaminant under natural conditions. We found evidence for depuration of perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS) and perfluorooctanoic acid (PFOA), but with depuration half-lives as high as 40 days (for PFOS). We also observed substantial variability in the data, including differences in PFAS concentrations between claws from the same individuals, potentially resulting from claw loss and re-growth prior to capture. These results have broad implications for assessing and minimising exposure risk in seafood species.

A preliminary ecological and human health risk assessment for organic contaminants in composted municipal solid waste generated in New South Wales, Australia.

Land application of composted municipal solid waste (C-MSW) can divert waste from landfill but can also be a route of entry into the environment for contaminants. This study presents a preliminary human health and ecological risk assessment for organic contaminants in C-MSW generated in New South Wales, Australia, to identify and prioritise contaminants of concern. Following an initial screening assessment, terrestrial and aquatic risks were assessed by predicted soil and water concentrations, respectively. The assessment ranked contaminants as very high, high, medium or low priority. A qualitative review was then used to identify contaminants of concern, which included polybrominated diphenyl ethers, phthalates, bisphenol A and dibutyltin. Phenol was initially categorised as very high priority but due to its rapid degradation in soil, this is likely to be overly-conservative. The herbicides dicamba and MCPA were categorised as medium priority or higher but due to uncertainties in the data, these categories are also likely to be overly-conservative. A range of contaminants had concentrations below the screening criteria and were therefore considered low risk. Many contaminants were below the limit of reporting in all samples and were therefore not considered to be sufficiently distributed in the material to pose a risk. Some contaminants were detected in the material but could not be assessed as no criteria were available. The information from this study can be used by regulators when managing land application of C-MSW to ensure that the risks to human health and the environment are managed appropriately.

Do conventional cooking methods alter concentrations of per- and polyfluoroalkyl substances (PFASs) in seafood?

Per-and poly-fluoroalkyl substances (PFASs) are bioaccumulative chemicals of emerging concern. Some PFASs accumulate in seafood, and can contribute to dietary exposure. Previous work has suggested cooking seafood decreases concentrations of neutral organic contaminants, however, previous studies dealing with PFASs have shown conflicting results. In this study, the potential changes of PFAS concentrations as a result of boiling, frying and baking are systematically examined. Blue Swimmer Crab (Portunus armatus), Dusky Flathead (Platycephalus fuscus) and School Prawn (Metapenaeus macleayi) were obtained from near a known PFAS point source and a reference location (affected by diffuse sources). Raw and cooked samples were analysed for commonly found PFASs. Of 23 target analytes, PFOS was the most frequently detected compound. PFOS, PFHxS and PFOA concentrations in School Prawn effectively doubled after boiling, and PFOS increased when Dusky Flathead was baked. There was no significant difference in PFOS concentration when Dusky Flathead was fried, or when the Blue Swimmer Crab was boiled. PFHxS and PFOA concentrations in Blue Swimmer Crab effectively halved after boiling. Increase in PFAS concentrations possibly arise from mass loss during the cooking process. Our data show that cooking does not consistently reduce PFAS concentrations, and cannot mitigate dietary exposure.

Bioaccumulation of perfluoroalkyl substances in exploited fish and crustaceans: Spatial trends across two estuarine systems.

Spatial patterns in perfluoroalkyl substances were quantified for exploited fish and crustaceans across two contrasting Australian estuaries (Port Stephens and Hunter River). Perfluorooctane sulfonate (PFOS) was detected in 77% of composites from Port Stephens and 100% of composites from Hunter River. Most species from Port Stephens showed a clear trend with distance to source. In contrast, only a subset of species showed this trend in the Hunter River, potentially due to species movement patterns and differing hydrology. Spatial modelling showed that PFOS concentrations were expected to exceed the relevant trigger value up to ~13,500 m from the main point source for Port Stephens and ~9000 m for the Hunter River. These results represent the first major investigation of bioaccumulation of PFASs in exploited species in Australian estuaries, and highlight various factors that can contribute to spatial patterns in bioaccumulation.

Depuration of perfluoroalkyl substances from the edible tissues of wild-caught invertebrate species.

Detection and quantification of poly- and perfluoroalkyl substances (PFASs) in aquatic organisms is increasing, particularly for saltwater species. Depuration can remove PFASs from the tissues of some species once they are removed from the contaminant source, but it is not known if this process occurs for saltwater crustaceans. Such information is important for managing human health risks for exploited migratory species following exposure. We present the results of a depuration trial for School Prawn (Metapenaeus macleayi) and Mud Crab (Scylla serrata), two commercially important crustaceans in Australia. Perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorooctanoic acid (PFOA) were present in samples of both species collected following exposure under natural conditions in contaminated estuaries. Depuration was tested in uncontaminated water for 33days. PFOA was present at levels close to LOR in both species, and was not detected after 4.5h and 72h in School Prawn and Mud Crab respectively. PFHxS was rapidly depurated by School Prawn, and had a depuration half-life of 5.7h. PFOS was also depurated by School Prawn, with a depuration half-life of 158.5h. PFHxS and PFOS concentrations were highly variable in Mud Crab both at the start, and during the depuration experiment, and a depuration model could not be fitted to the data. For School Prawn, depuration of total PFASs to the relevant screening value for protection of human health (9.1µgkg-1) occurred within 7.1h. Rapid depuration of PFASs in School Prawn indicates that human health risks associated with consumption may decrease as this species migrates away from the contamination source. Further research is required to better understand the relationships between contaminant load and life-history characteristics (such as growth, reproduction, and moult cycle) in Mud Crab, and future work should target broader time frames for depuration in this species.

The biotic ligand model: a historical overview.

During recent years, the biotic ligand model (BLM) has been proposed as a tool to evaluate quantitatively the manner in which water chemistry affects the speciation and biological availability of metals in aquatic systems. This is an important consideration because it is the bioavailability and bioreactivity of metals that control their potential to cause adverse effects. The BLM approach has gained widespread interest amongst the scientific, regulated and regulatory communities because of its potential for use in developing water quality criteria (WQC) and in performing aquatic risk assessments for metals. Specifically, the BLM does this in a way that considers the important influences of site-specific water quality. This journal issue includes papers that describe recent advances with regard to the development of the BLM approach. Here, the current status of the BLM development effort is described in the context of the longer-term history of advances in the understanding of metal interactions in the environment upon which the BLM is based. Early developments in the aquatic chemistry of metals, the physiology of aquatic organisms and aquatic toxicology are reviewed first, and the degree to which each of these disciplines influenced the development of water quality regulations is discussed. The early scientific advances that took place in each of these fields were not well coordinated, making it difficult for regulatory authorities to take full advantage of the potential utility of what had been learned. However, this has now changed, with the BLM serving as a useful interface amongst these scientific disciplines, and within the regulatory arena as well. The more recent events that have led to the present situation are reviewed, and consideration is given to some of the future needs and developments related to the BLM that are envisioned. The research results that are described in the papers found in this journal issue represent a distinct milestone in the ongoing evolution of the BLM approach and, more generally, of approaches to performing ecological assessments for metals in aquatic systems. These papers also establish a benchmark to which future scientific and regulatory developments can be compared. Finally, they demonstrate the importance and usefulness of the concept of bioavailability and of evaluative tools such as the BLM.

Metal sulfides in oxygenated aquatic systems: implications for the biotic ligand model.

The Biotic Ligand Model (BLM) attempts to predict metal toxicity to aquatic organisms on the basis of metal speciation and effects at the cell surface. Current versions of the BLM for silver and copper consider metal binding by inorganic ligands, dissolved organic matter (DOM) and also competition at the cell surface from calcium and protons (pH). Recent studies reported in the geochemical and ecotoxicological literature have indicated the importance of sulfide as a ligand, even in fully oxygenated aquatic systems. Speciation calculations for oxygenated waters do not currently include reduced sulfur as a ligand and as a consequence, no version of the BLM model has been published including reduced sulfur. This reflects the limitations on our knowledge regarding reduced sulfur in aquatic systems. In this paper we highlight the need to include reduced sulfur in the Biotic Ligand Model, with the interaction between silver and inorganic metal sulfides as a specific example. The geochemical importance of metal sulfides as ligands for silver and the effect of 'dissolved' metal sulfide and other ligands on metal toxicity and accumulation are described and reviewed. Recommendations are made for future work needed to incorporate sulfide ligands into the BLM's modeling framework.

Evaluation of the effect of reactive sulfide on the acute toxicity of silver (I) to Daphnia magna. Part 2: toxicity results.

The protective effect of reactive sulfide against AgNO3 toxicity to Daphnia magna neonates was studied. Acute (48-h) toxicity tests were performed in the absence (<5 nM) and presence of low (approximately 25 nM) and high (approximately 250 nM) concentrations of zinc sulfide clusters under oxic conditions. In both the presence and the absence of sulfide, lower mean lethal concentration (LC50) values were observed when measured as opposed to nominal silver concentrations were used in calculations. This reflected the fact that measured total silver concentrations were lower than nominal concentrations due to losses of silver from solution observed during the experiment. High concentration (approximately 250 nM) of sulfide completely protected against toxicity up to the highest silver concentration tested (2 microg/L [19 nM]) with measured silver data. In the presence of environmentally realistic levels of sulfide (approximately 25 nM) in receiving waters, acute silver toxicity was reduced by about 5.5-fold. However, when filtered (0.45 microm) silver concentrations alone were considered, toxicity (48-h LC50) was similar in the absence (0.22 microg/L) and presence (0.28 microg/L) of sulfide. The difference between measured total and filtered silver was attributed to chemisorption of the metal sulfide onto the membrane filter and provides evidence that the toxic fraction of silver is that which is unbound to sulfide. Accumulation of silver was greater in daphnids exposed to silver in the presence of sulfide than in its absence, even though a toxic effect was not observed under these conditions. In this case, silver appears to be incorporated by daphnids rather than merely adsorbed on the surface. Our results point out the need to incorporate sulfide into the acute biotic ligand model and to assess its potentially large role in preventing chronic toxicity.

Evaluation of the effect of reactive sulfide on the acute toxicity of silver (I) to Daphnia magna. Part 1: description of the chemical system.

Experiments were designed to assess the potential protective effect of the presence of sulfide against the acute (48-h) toxicity of silver(I) to Daphnia magna. Tests were conducted in borosilicate glass beakers (250 ml) in moderately hard synthetic water. Toxicity solutions were replaced after 24 h by static renewal method. This paper describes the chemical system, and the acute toxicity results are presented in a companion paper. Sulfide was below detection limit (<5 nM) in controls with no sulfide added. Sulfide, added as zinc sulfide clusters at approximately 35- or approximately 350-nM concentration, dropped in concentration to approximately 25 and 250 nM, respectively, over the 24-h period of measurements. Silver also decreased in concentration during the experiment (up to 59%), and the rate of loss was greater in the absence of sulfide compared with the presence of sulfide. A filtration experiment indicated a 1:1 binding ratio of silver to sulfide and a conditional stability constant for the Ag(I)-zinc sulfide complex of log K' = 8.9. The losses of sulfide and silver during the experiments highlighted the need for regular monitoring of the important chemical components of the system, even during short (48-h) toxicity tests.