PFAS Distribution in Contaminated Soils and Impact on Rhizosphere and Plant Microbiota

Abstract:

Rhizosphere horizons are particularly susceptive to heavy metal and organic contaminants accumulation, due to their specific biogeochemical processes enhanced by high organic matter and nutrient content. In our research, we investigate the role of the plant endophytes and rhizosphere microorganisms as main drivers for contaminant bioavailability. In particular, we have focused on evaluating the distribution of PFAS in plants exposed to mixed contaminants, and their effect in the rhizosphere and in planta microbial community. Field measurements are combined with in vitro and hydroponic experiments to assess the mechanisms of PFAS plant translocation and microbiome changes. This work focuses on the Ringwood/Ford Superfund, NJ site where lead, arsenic, chloroethane, benzene and 1,4-dioxane are the main contaminants of concern. However, PFAS have been measured in water, sediments and plants at different locations. PFNA, PFOA and PFOS have been analyzed in 8 locations, and elevated PFAS concentration was found in one location downstream a paint sludge disposal area (PFOS 445 ng/L, PFOA 23.78 ng/L, PFNA 25.69 ng/L). PFAS were also measured in sediments (PFOS 2.18 ng/g), rhizosphere (PFOS 2.45 ng/g) and plants (PFOS 0.811 ng/g roots). Laboratory experiments showed that endophytic microbial community decreased PFAS toxicity to Poa reptans seedlings. Plant production of oxygen species (ROS) secretion into the root zone was reduced in the presence of endophytic microbes. PFAS exposure resulted in damage to the root hairs and lack of internal cyclosis only in the absence of bacteria (bleached seeds). Hydroponic investigation on PFAS uptake by Arabidopsis thaliana shows PFOA preferred accumulation in roots, and a direct relationship with PFAS solution concentration. Furthermore, PFOA exposure changed the microbiome of Arabidopsis thaliana. Ongoing research is continuing to investigate PFAS mixtures to elucidate the differences between different functional groups, C-chain length, and different biochemical properties. This work is expected to provide a holistic understanding of the fate and transformation of PFAS within the various environmental compartments, and it will inform future remediation strategies and exposure prevention alternatives.