Geochemical Factors Controlling the Release of Poly- and Perfluoroalkyl Substances from AFFF-Impacted, Source Zone Soils.

Strategic Environmental Research and Development Program (SERDP)
Oral Presentation

Prepared by , C. Higgins

Contact Information: [email protected]; 510-907-0339


Aqueous film-forming foams (AFFF) manufactured by 3M, Ansul, and National Foam have been found to contain polyfluorinated compounds at concentrations exceeding those of the perfluorocarboxylic acids, though the reverse is typically observed in AFFF-impacted groundwaters. The loss of these, often cationic or zwitterionic, polyfluorinated compounds may derive from their preferential retention by source-zone soils. Therefore, we examined the role of soil characteristics and geochemical conditions on the retention of poly- and perfluoroalkyl substances (PFASs) by AFFF-impacted soils. AFFF-impacted soils were packed into glass columns through which artificial groundwater was pumped. PFAS retention by sterilized soils was also evaluated to control for biodegradation. PFASs were quantified in column effluents, and in soils prior and following exposure to artificial groundwater. 44 “target” PFAS were quantified through comparison with reference standards and 13C-labeled surrogates by LC-QToF-MS, with an SCIEX Q500R. To ensure detection of the often zwitterionic or cationic polyfluorinated PFASs, analysis was repeated with both negative and positive polarity electrospray. As reference standards are not available for many polyfluorinated compounds of interest, “suspect” compounds were identified by comparison of MS/MS fragmentation spectra against an extensive MS/MS spectral library, developed in conjunction with SCIEX. Where fragmentation spectra were unavailable, additional “suspect” compounds were identified by comparison of accurate parent mass against an extracted ion chromatogram list, which contained compounds identified in literature or speculated to be present at AFFF-impacted sites. Complementary techniques, including TOP assay and TOF, were used to determine the potential mass of precursor compounds present in the AFFF-impacted soils. PFAS compound retention was found to vary according to the combined effects of soil characteristics and geochemical conditions, with the relative importance of each varying according to the chemical characteristics of individual PFAS compounds. This research was conducted as part of the SERDP-funded project ER-2720.