POTENTIAL FOR AGE-DATING LANDFILL LEACHATE RELEASES USING PFAS COMPOUNDS

While the presence or absence of per- and polyfluoroalkyl substances (PFAS) compounds, or “forever chemicals”, has proven to be an excellent marker for detecting landfill leachate contamination, recent research has shown that attempts to use individual PFAS compounds as specific leachate source or age tracers is problematic. This is because some type(s) of chemical transformation appears to be happening to PFAS compounds inside of landfills. A possible exception to this is perfluorobutanesulfonic acid (PFBS), a shorter-chain PFAS that has been used as a replacement for the longer-chain perfluorooctanesulfonic acid (PFOS), which has been phased out by major PFAS manufacturers since the early 2000s. Some published studies indicate that PFBS and other shorter-chain PFASs can be detected at higher concentrations in leachate from newer landfills as opposed to leachate from older landfills. In this study, involving groundwater contamination data from a landfill complex with both newer, lined Subtitle D cells and older, unlined pre-Subtitle D disposal areas, PFBS concentrations were compared to those of total perfluorooctanoic acid (PFOA) and PFOS. Results showed that this ratio (PFBS to ∑PFOA+PFOS) decreased with distance from the newer Subtitle D landfill cells.