MITIGATION OF PFAS IN AGRICULTURAL FIELDS USING SORBENTS MATERIALS

With advances in human development comes many effects which may be good, bad, or ugly. One evidently not so good effect is the constant pollution of the environment by the anthropogenic activities of man. Per- and polyfluoroalkyl substances (PFAS) are a special class of man-made chemicals that are ubiquitous, recalcitrant and toxic with a tendency to bioaccumulate and bio-magnify along the food chain. PFAS get into agricultural soil primarily through wet/dry deposition, irrigation with PFAS-contaminated water, and land application of biosolids as fertilizers. While biosolids are a great source of slow-release nutrients that plants love, PFAS presence in biosolids raises concern about sustainable biosolids land application practices and safe operation of farms that are already contaminated with PFAS. There is therefore the need to find practical methods for reducing PFAS release from biosolids and mitigating PFAS fate in already contaminated agricultural fields. In this study, we employed immobilization strategies via a series of batch sorption experiments, a column study, a greenhouse study and a field study by using four sorbent materials (pyrolyzed biosolids, ACH-WTR, wood-ash and wood-biochar) for the mitigation of PFAS in PFAS contaminated agricultural soils and land applied biosolids. Overall results showed that that sorption of perfluoroalkyl acids, including the perfluoroalkylsulfononic acids (PFSAs) such as PFHxS and PFOS, increased with increasing ACH-WTR concentrations in batch sorption experiments. In the six-month long column study, leachates from ACH-WTR-amended columns contained 32% less total PFAS compared to those from biosolids-only control columns, with PFOS mobility specifically reduced by 68%. Likewise, amending PFAS-contaminated soils with 6 wt% wood-ash decreased total PFAS uptake in grass leaves by 83% and significantly enhanced plant growth in the 1-year long, multiple harvest greenhouse study. Correspondingly, soil-to-plant translocation factors (TFs) were significantly lower (P < 0.01) in the 3 wt% and 6 wt% wood-ash treatments than in the control for most PFAS. First-year field results indicate that both wood-ash and wood-biochar amendments can reduce PFAS uptake into grass leaves, with wood-ash exhibiting greater effectiveness. However, evaluating field-scale efficacy requires additional data from at least a second harvest season given climate impacts on soil moisture impacting plant uptake of PFAS. Results from this dissertation research provides insights into the potential benefits and cautions in application of PFAS immobilization strategies for minimizing negative consequences of PFAS presence in biosolids and agricultural systems.