Assessment of Mobilization Potential of Per- and Polyfluoroalkyl Substances for Soil Remediation.

This study investigated the mobilization of a wide range of per- and polyfluoroalkyl substances (PFASs) present in aqueous film-forming foams (AFFFs) in water-saturated soils through one-dimensional (1-D) column experiments with a view to assessing the feasibility of their remediation by soil desorption and washing. Results indicated that sorption/desorption of most of the shorter-carbon-chain PFASs (C ≤ 6) in soil reached greater than 99% rapidly─after approximately two pore volumes (PVs) and were well predicted by an equilibrium transport model, indicating that they will be readily removed by soil washing technologies. In contrast, the equilibrium model failed to predict the mobilization of longer-chain PFASs (C ≥ 7), indicating the presence of nonequilibrium sorption/desorption (confirmed by a flow interruption experiment). The actual time taken to attain 99% sorption/desorption was up to 5 times longer than predicted by the equilibrium model (e.g., ∼62 PVs versus ∼12 PVs predicted for perfluorooctane sulfonate (PFOS) in loamy sand). The increasing contribution of hydrophobic interactions over the electrostatic interactions is suggested as the main driving factor of the nonequilibrium processes. The inverse linear relationship (R2 = 0.6, p < 0.0001) between the nonequilibrium mass transfer rate coefficient and the Freundlich sorption coefficient could potentially be a useful means for preliminary evaluation of potential nonequilibrium sorption/desorption of PFASs in soils.

Comparing the Leaching Behavior of Per- and Polyfluoroalkyl Substances from Contaminated Soils Using Static and Column Leaching Tests.

Soil contaminated with aqueous film-forming foams (AFFFs) containing per- and polyfluoroalkyl substances (PFASs) at firefighting training sites has become a major concern worldwide. To date, most studies have focused on assessing soil-water partitioning behavior of PFASs and the key factors that can affect their sorption, whereas PFASs leaching from contaminated soils have not yet been widely investigated. This study evaluated the leaching and desorption of a wide range of PFASs from twelve contaminated soils using the Australian Standard Leaching Procedure (ASLP), the U.S. EPA Multiple Extraction Procedure (MEP), and Leaching Environmental Assessment Framework (LEAF). All three leaching tests provided a similar assessment of PFAS leaching behavior. Leaching of PFASs from soils was related to C-chain lengths and their functional head groups. While short-chain (CF2 ≤ 6) PFASs were easily desorbed and leached, long-chain PFASs were more difficult to desorb. PFASs with a carboxylate head group were leached more readily and to a greater extent than those with a sulfonate or sulfonamide head group. Leaching of long-chain PFASs was pH-dependent where leaching increased at high pH, while leaching of short-chain PFASs was less sensitive to pH. Comparing different leaching tests showed that the results using the alkaline ASLP were similar to the cumulative MEP data and the former might be more practical for routine use than the MEP. No single soil property was adequately able to describe PFAS leaching from the soils. Overall, the PFAS chemical structure appeared to have a greater effect on PFAS leaching from soil than soil physicochemical properties.

Spatial and temporal trends of 64 pesticides and their removal from Australian wastewater.

Pesticides are necessary for the control of pest plant, fungi and insect species. After application, they may find their way into waste streams, such as municipal sewage, where their spatio-temporal distribution has not been well characterised. To further understand the spatio-temporal distribution and to evaluate potential sources and fate after treatment, 64 pesticides were analysed in matched influents and effluents of 22 wastewater treatment plants (WWTPs) from across Australia. The pesticides consisted of 30 herbicides and 8 herbicide metabolites or transformation products, 16 insecticides and 10 fungicides. The samples were 1084 24-hr composite samples pooled into 113 samples. Pools represented two influent and one effluent pools at each of 22 sites in 2019, as well as two pools per year from 2009 to 2021 for an 11-year long-term temporal trend at a subset of two locations. The total population served by the 22 sites was equivalent to ~41 % of the Australian population. Of the 64 pesticides, 25 were detected in influent, with highest influent concentrations up to 100 µg/L and effluent concentrations up to 16 µg/L for the herbicide 2,4-D. The total mass of pesticides was extrapolated to Australia, suggesting ~33 t of the targeted pesticides entered WWTP influent annually nation-wide, with 14 t emitted into effluents annually. Long-term trends varied by analyte and for carbendazim decreases over time, may be related to restrictions in use. Risk quotients (RQs) were calculated for 14 analytes in the effluent. 35 % had an RQ above one, indicating a potential environmental risk. Fipronil had the highest RQ (49) at Site 6. The population-normalized mass loads of pesticides were site-specific, and in some cases correlated with land use attributes suggestive of point sources. This reflects a need to better characterise sources to enable prevention, or possible pre-treatment of pesticide-containing wastewater entering municipal sewage streams.

Calibration of a microporous polyethylene tube passive sampler for polar organic compounds in wastewater effluent.

Water resources are vulnerable to contamination from polar organic compounds (POCs) originating from sources such as wastewater effluent. Two configurations of a microporous polyethylene tube (MPT) passive sampler were investigated for the time-integrative detection and quantification of POCs in effluent. One configuration contained the polymeric reversed phase sorbent Strata-X (SX) and the other Strata-X suspended in agarose gel (SX-Gel). These were deployed for up to 29 days and analysed for forty-nine POCs including pesticides, pharmaceuticals and personal care products (PPCPs) together with illicit drugs. Complementary composite samples were collected on days 6, 12, 20 and 26 representing the previous 24 h. Thirty-eight contaminants were detected in composite samples and MPT extracts, with MPT sampling rates (Rs) for 11 pesticides and 9 PPCPs/drugs ranging from 0.81 to 10.32 mL d-1 in SX and 1.35-32.83 mL d-1 in SX-Gel. Half-times to equilibrium of contaminants with the SX and SX-Gel equipped samplers ranged from two days to >29 days. MPT (SX) samplers were also deployed at 10 wastewater treatment effluent discharge sites across Australia for 7 days (again with complementary composite samples), to validate the sampler performance under varying conditions. Extracts from these MPTs detected 48 contaminants in comparison with 46 in composite samples, with concentrations ranging from 0.1 to 138 ng mL-1. An advantage of the MPT was preconcentration of contaminants, resulting in extract levels often markedly above instrument analytical detection limits. The validation study demonstrated a high correlation between accumulated contaminant mass in the MPTs and wastewater concentrations from composite samples (r2 > 0.70, where concentrations in composite samples were > 3× LOD). The MPT sampler shows promise as a sensitive tool for detecting POCs at trace levels in wastewater effluent and also quantifying these levels if temporal concentration variations are not significant.

The efficacy of soil washing for the remediation of per- and poly-fluoroalkyl substances (PFASs) in the field.

This paper aims to describe the performance of a soil washing plant (SWP) for remediating a per- and poly-fluoroalkyl substances (PFASs)-contaminated soil with a high clay content (61%). The SWP used both physical and chemical processes; fractionation of the soil particles by size and partitioning of PFASs into the aqueous phase to remove PFASs from the soil. Contaminated water was treated in series with granulated activated carbon (GAC) and ion-exchange resin and reused within the SWP. Approximately 2200 t (dry weight) of PFAS-contaminated soil was treated in 25 batches of 90 t each, with a throughput of approximately 11 t soil/hr. Efficiency of the SWP was measured by observed decreases in total and leachable concentrations of PFASs in the soil. Average removal efficiencies (RE) were up to 97.1% for perfluorocarboxylic acids and 94.9% for perfluorosulfonic acids. REs varied among different PFASs depending on their chemistry (functional head group, carbon chain length) and were independent of the total PFAS concentrations in each soil batch. Mass balance analysis found approximately 90% of the PFAS mass in the soil was transferred to the wash solution and > 99.9% of the PFAS mass in the wash solution was transferred onto the GAC without any breakthrough.

An investigation into the long-term binding and uptake of PFOS, PFOA and PFHxS in soil - plant systems.

This study investigated the potential aging and plant bioaccumulation of three perfluoroalkyl acids (PFAAs), perfluorosulphonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexanesulphonic acid (PFHxS) in 20 soils over a six-month period. Sorption coefficients (Log Kd) ranged from 0.13-1.28 for PFHxS, 0.17-1.06 for PFOA and 0.98-2.03 for PFOS, respectively, and bioaccumulation factors (Log BAFs) ranged from 0.29-1.24, 0.22-1.46 and 0.05-0.65 for PFHxS, PFOA and PFOS, respectively. Over the six-month period, Kd values significantly increased for PFHxS and PFOA but the magnitude of the increase was very small and did not translate into differences in plant PFAA-concentrations between aged and freshly spiked treatments. The Kd and BAF values were modelled by multiple linear regression (MLR) to soil physico-chemical properties and by partial least squares regression to soil spectra acquired by mid-infrared spectroscopy (DRIFT-PLSR). Modelling of each PFAA was influenced by different soil properties, including organic carbon, pH, CEC, exchangeable cations (Ca2+, Mg2+, Na+ and K+) and oxalate extractable Al. BAF values were not strongly correlated to any soil property but were inversely correlated to Kd values. Our results indicate that limited aging occurred in these soils over the six-month period.

Sorption of PFOA onto different laboratory materials: Filter membranes and centrifuge tubes.

Measurement and reporting of concentrations of contaminants of emerging concern such as per- and polyfluoroalkyl substances (PFASs), including perfluorooctanoic acid (PFOA), is an integral part of most investigations. Occurrence of sorption losses of PFAS analytes onto particular laboratory-ware (e.g. glass containers) has been suggested in the published literature but has not been investigated in detail. We examined sorption losses from aqueous PFOA solutions in contact with different commonly-used materials in filter units and centrifuge tubes (glass and plastics). Sorption of PFOA onto different filter membrane types ranged from 21-79% indicating that filtration can introduce a major source of error in PFOA analysis; pre-treatment of filter membranes with phosphate or methanol solutions did not improve PFOA recovery. Substantial adsorption of PFOA was also observed on tubes made from polypropylene (PP), polystyrene (PS), polycarbonate (PC), and glass where losses observed were between 32-45%, 27-35%, 16-31% and 14-24%, respectively. Contrary to suggestions in the literature, our results indicated that the greatest sorption losses for PFOA occurred on PP, whereas losses on glass tubes were much lower. Variations in ionic strength and pH did not greatly influence PFOA recovery. When PFOA concentrations were increased, the percent recovery of PFOA increased, indicating that binding sites on tube-walls were saturable. This study draws attention towards analytical bias that can occur due to sorption losses during routine procedures, and highlights the importance of testing the suitability of chosen laboratory-ware for specific PFAS analytes of interest prior to experimental use.

Predicting partitioning of radiolabelled 14C-PFOA in a range of soils using diffuse reflectance infrared spectroscopy.

The aim of this study was to establish partitioning coefficients (Kd) of perfluorooctanoic acid (PFOA) in a wide range of soils and determine if those values can be predicted from soil properties using multiple linear regression (MLR) and from infrared spectra of soils using partial least squares regression (PLSR). For 100 different soils, the Kd values of spiked radiolabelled 14C-PFOA ranged from 0.6 to 14.8 L/kg and significantly decreased with soil depth (p < 0.05) due to soil properties that change with depth. The MLR modelling revealed that PFOA sorption was significantly (p < 0.05) influenced, in decreasing order, by organic carbon (OC) content, silt-plus-clay content and soil pH. Soils were partitioned into all soils and surface soils alone. The MLR models using OC, silt-plus-clay content and pH together explained most of the variation in sorption in all soils as well as surface soils alone (0-15 cm). However, correlations between soil properties and Kd values in some soils could not be explained by the MLR model. Modelling of Kd prediction in soils with PLSR and diffuse reflectance (mid) infrared Fourier transform spectroscopy (DRIFT) showed comparable success in explaining the predictions of Kd values, including some of the outliers identified in the MLR model. The PLSR loading weights suggested that quartz, and possibly pyrophyllite minerals, were inversely correlated with the Kd values. Given that MLR requires a-priori characterisation of a range of soil properties and PLSR-DRIFT is a method based on the direct relationship between spectra and soil components, mid-infrared spectroscopy may be a more economical and rapid technique to predict the solid-liquid partitioning of PFOA in soils.

Bioaccumulation, uptake, and toxicity of carbamazepine in soil-plant systems.

Since the detection of active pharmaceutical ingredients (APIs) in various environmental media, research has explored the potential uptake and toxicity of these chemicals to species inhabiting these matrices. Specifically, pharmaceuticals, including the antiepileptic API carbamazepine (CBZ), are taken up from soil by a range of plants. Many short-term studies have also suggested that certain APIs induce toxicity in plants. However, the effects of APIs on fruiting plants remain relatively unexplored. The present study investigated the uptake, bioaccumulation, and toxicity of CBZ in Cucurbita pepo (zucchini) from seed to full maturity across a range of CBZ exposure concentrations in soil (0.1-20 mg/kg). Results of biomass, chlorophyll, starch and total nitrogen (N) concentration in C. pepo indicated toxicity at soil concentrations of ≥10 mg/kg. There were clear visual indications of increasing toxicity on leaves, including chlorosis and necrosis, from soil concentrations of 1 up to 20 mg/kg. The present study also revealed novel insights into the effect of CBZ accumulation on C. pepo fruiting: female C. pepo flowers were unable to set fruit when leaf concentrations were ≥14 mg/kg. These findings may have implications for future agricultural productivity in areas where reclaimed wastewater containing APIs is a source of irrigation. Detectable CBZ concentrations were found in edible C. pepo fruit, indicating the possibility of trophic transfer. Environ Toxicol Chem 2018;37:1122-1130. © 2017 SETAC.