Recent lab work has demonstrated that activated persulfate can degrade PFOS, and the degradation mechanism is hypothesized to be a combination of oxidation and reduction as defluorination. Decreases in PFOS concentrations were observed only when a specific activation method was employed: the "Smart combined in situ oxidation and Reduction" (ScisoR®) technology. Lab data demonstrated that this technology results in defluorination indicative of PFOS mineralization. A mass balance demonstrated stoichiometric conversion of PFOS to fluoride. ScisoR was used for destruction of numerous PFAS precursors and perfluorinated alkyl acids (e.g., PFOS) in soil and groundwater sampled from an AFFF-impacted site in Scandinavia. Based upon a variety of analytical methods, PFASs were shown to be mineralized using ScisoR, whereas conventional oxidants transformed precursors to perfluorinated alkyl acids.