Comparative characterization of microbial communities that inhabit PFAS-rich contaminated sites: A case-control study.

The historic usage and discharge of per- and polyfluoroalkyl substances (PFAS) containing chemicals have produced many contaminated sites and PFAS contamination has become a global concern due to their persistence, widespread distribution, and potential adverse impacts for human and environmental health. However, there have been limited investigations on the specific behavior of bacterial communities in PFAS contaminated soils. In this study, a quantitative PCR assay and Illumina MiSeq sequencing were used to investigate the variations of bacterial communities in a regional Australian airport contaminated with PFAS. The dominate PFAS detected in soil samples was Perfluorooctanesulfonic acid (PFOS), which accounted for 82% of total PFAS and the maximum PFOS level was noted (20,947±1824 ng.PFOS/mg.Soil) at the top soil. Irrespective of the degree of PFAS contamination at different depths, the comparable percentile contribution of each PFAS was observed in soil samples. Significantly higher bacteria amplicon sequence variant (ASV) and diversity were noted in uncontaminated soil than PFAS contaminated soil. Bacterial genera Rhodanobacter and Chujaibacter were dominant in the PFAS contaminated soil. Three different bacterial genera of Alphaproteobacteria, Ambiguous taxa of Acidobacteriia, and genus Chujaibacter of Gammaproteobacteria showed a significant positive correlation and RB41, Gaiella showed a significant negative correlation with 11 different PFAS concentrations. Overall, the results presented in this study suggest that the counts and species diversity of soil microorganisms are adversely influenced by PFAS contamination.

The effect of particle shape on the deformation and stress reduction of a gravel soil due to wetting.

This paper investigates the effect of particle shape on the stress reduction and collapse deformation of gravelly soil using a medium-scale direct shear test apparatus under different relative densities, normal stress, and shear stress levels. A new method based on the Micro-Deval test was introduced to produce sub-angular particles from angular particles. Therefore, two series of soil specimens were obtained with the same rock origin, particle size distribution, and relative density but different particle shapes. In addition to traditional direct shear tests on dry and wet specimens, a specific test procedure was applied to explore the stress reduction and collapse of soil specimens due to wetting. The results of the tests, including shear stress-shear displacement and vertical displacement-shear displacement, were compared. The results showed that the stress reduction and settlement due to wetting increased with vertical and shear stress levels in both types of particle shapes, with higher values in angular particle shapes. The particle breakage of the soil specimens was also studied quantitatively using the change in the particle size distribution before and after the test. It was shown that the wetting of the samples had more impact on the particle breakage in angular gravel than sub-angular gravel, which increased linearly with the normal stress.

The effectiveness of PFAS management options on groundwater quality in contaminated land using numerical modelling.

The concentrations of PFOS and PFHxS in a contaminated site in regional New South Wales, Australia, were above the human health screening values for industrial land use. In this study, the effects of different management options on the quality of groundwater were investigated through numerical modelling. At first, a complete transfer model including the main features of advection, dispersion, adsorption and decay, was developed to simulate the long-term migration of PFOS from topsoil subjected to full climate interaction for 100 years. The sorption isotherm characteristics of the contaminated soil were determined from chemical analysis using LC/MS equipment. The model results were confirmed by PFOS values measured from a monitoring well in the proximity of the site. The model showed that PFOS values in groundwater increased gradually and exceeded the guideline values for drinking water. Three management options were suggested: a do-nothing approach, cut and replacement, and immobilisation of the topsoil up to 2 m depth. The numerical models showed that although all these strategies reduced the PFOS level in the groundwater significantly, the values were still higher than the guideline values for drinking water. This was because PFOS migrated in the ground beyond the site location. The cut and replacement and immobilisation strategies ensured that the PFOS values were lower than the guideline values for soil screening, but PFOS levels in the groundwater were not necessarily lower than the guideline values for drinking water after a long time.

In situ soil flushing to remediate confined soil contaminated with PFOS- an innovative solution for emerging environmental issue.

PerFluoroOctane Sulfonate (PFOS), is a toxic anthropogenic chemical that has been produced and gradually released into the environment for the past seven decades. An accurate audit of global PFOS contamination and contaminated sites are yet to be published. The available technologies to remediate PFOS contaminated soil are limited and often basic strategies such as temporary soil containment are adopted as immediate measures to manage the contaminated sites. In this study, the in situ soil flushing technique is assessed for its capacity to remediate soil contaminated with PFOS. A complete treatment process with several operation units was proposed such as solvent flushing, ground water pumping, solvent recovery and water treatment for PFOS. Potential solvents were identified and it was observed that more than 98% PFOS removal could be attained by flushing with five bed volumes of 50% ethanol. In addition, the study investigated thirteen commercially available filter materials and identified PFA694E, K6362, MP 62, Amberlite IRA 67 and Dowexoptopore V493 as suitable to eliminate PFOS with competitive PFOS adsorption characteristics. The proposed method can be recommended to remediate PFOS in recognised contaminated soils, such as those at defence sites. Furthermore, a contaminated site with favourable characteristics to implement the suggested method was identified in Australia and described in this paper.

A review of the emerging treatment technologies for PFAS contaminated soils.

Contamination of soils with poly- and perfluoroalkyl substances (PFAS) has become a challenging issue due to the adverse effects of these substances on both the environment and public health. PFAS have strong chemical structures and their bonding with soil makes them challenging to eliminate from soil environments. Traditional methods of soil remediation have not been successful in their reduction or removal from the environment. This paper provides a comprehensive evaluation of existing and emerging technologies for remediating PFAS contaminated soils with guidance on which approach to use in different contexts. The functions of all remediation technologies, their suitability, limitations, and the scale applied from laboratory to the field are presented as a baseline for understanding the research need for treatment in soil environments. To date, the immobilization method has been a significant part of the remediation solution for PFAS contaminated soils, although its long-term efficiency still needs further investigation. Soil washing and thermal treatment techniques have been tested at the field scale, but they are expensive and energy-intensive due to the use of a large volume of washing solvent and the high melting point of PFAS, respectively; both methods need a large initial investment for their installation. Other remediation technologies, such as chemical oxidation, ball milling, and electron beams, have been progressed in the laboratory. However, additional research is needed to make them feasible, cost-effective and applicable in the field.