Release of Per- and Polyfluoroalkyl Substances from Aqueous Film-Forming Foam Impacted Soils

Abstract

Per- and polyfluoroalkyl substances (PFASs) are highly mobile in the saturated subsurface, yet aqueous film-forming foam (AFFF)-impacted source zones appear to be long lasting PFAS reservoirs. This study examined the release of over one hundred anionic and zwitterionic PFASs from two AFFF-impacted surface soils under saturated conditions with packed soil columns. Perfluoroalkyl acids (PFAAs) were released more rapidly than their polyfluorinated precursors, while anionic PFASs that were present in partially uncharged states were released more slowly than PFASs that were present entirely as anions, as were zwitterionic PFASs with terminal cationic functional groups when compared with analogous zwitterions with only anionic terminal groups. Nonideal transport was observed in both per- and polyfluorinated classes, as soil column effluent concentrations of slowly released PFASs increased by up to 107-fold with sustained artificial groundwater flow. A flow-interruption experiment suggested the influence of rate-limited desorption on diverse PFAS classes, including PFAAs with as few as four perfluorinated carbons. These results suggest that during infiltration the slow, rate-limited desorption of anionic and zwitterionic PFAA precursors may result in these compounds comprising an increasingly large fraction of the remaining PFASs in AFFF-impacted surface soils.

Communicating Confidence of Per- and Polyfluoroalkyl Substance Identification via High-Resolution Mass Spectrometry

“…The measured mass of features prioritized by suspect screening must be accurate with the proposed exact mass and within a certain tolerable error of PFASs on a suspect list. 32 …”

Simulating Impacts of Biosparging on Release and Transformation of Poly- and Perfluorinated Alkyl Substances from Aqueous Film-Forming Foam-Impacted Soil

“…To compare the oxygen and nitrogen-sparged data to an unaltered baseline, data collected from a previous study were included: the previous study used the same soil and experimental setup to analyze abiotic PFAS release (Soil B in Maizel et al) . The previous columns were concluded to be nonbiologically active, at least in terms of PFAS transformation, by comparisons with sterilized soil (via γ-irradiation).…”

“…The post-elution soils and the original soil were extracted and analyzed via the method of Nickerson et al 23 To compare the oxygen and nitrogen-sparged data to an unaltered baseline, data collected from a previous study were included: the previous study used the same soil and experimental setup to analyze abiotic PFAS release (Soil B in Maizel et al). 24 The previous columns were concluded to be nonbiologically active, at least in terms of PFAS transformation, by comparisons with sterilized soil (via γirradiation). The nonsterilized soil columns showed no differences in PFAS elution or concentrations when compared to sterilized soil columns.…”

“…Maizel et al provides in-depth discussions of how class and chain length relate to elution profiles, which also apply to the results of this study. 24 Higher Concentrations of Certain PFASs Eluted from O 2 -Sparged Columns. When comparing elution profiles from the O 2 -sparged and N 2 -sparged columns, several PFASs eluted at higher concentrations from the O 2 -sparged columns around pore volumes 11−25 (days 5−13) based on visual comparison of the concentration ranges.…”

“…The fractions eluted from the O 2 -sparged and N 2 -sparged columns were compared to data from unaltered, non-biostimulated columns containing the same soil. 24 Since the O 2 -sparged columns ran for longer than the N 2 -sparged and unaltered columns, only data up to pore volume 196 were used in this comparison.…”