PFAS LEACHING AND TRANSFORMATIONS IN MUNICIPAL SOLID WASTE LANDFILLS: FROM CONSUMER PRODUCTS TO LEACHATE

Municipal solid waste landfills (MSWLs) are an integral component of the engineered environment, and serve as terminal repositories for commercial, consumer, and industrial solid wastes. Observed trends in MSWLs reveal a distinct incongruity between composition of PFAS entering in waste, mostly as diPAP and FTOH, and leaching as FTCA and PFCA. These patterns are elucidated by compiling reported PFAS compositions in paper, textiles, and carpet, and known precursor transformations responsible for FTCA and PFCA predominance in leachate. PFAS transformations in MSWLs have been documented in bioreactor and leaching tests with MSW and carpet, which demonstrate that biodegradation of these substrates enhances PFAS release. These phenomena explain why MSWLs in wetter climates with higher leachate flow volumes are correlated with higher PFAS concentrations. The higher water content within the landfill may stimulate biologic activity, dilute competing cations, and increase leaching, biotransformation, and transport. It is critical that future research assess the role of PFAS precursors (e.g., diPAP and FTOH) in landfill mass balances, particularly in leachate, along with the potential for release of semi-volatile PFAS to the atmosphere. Closing these knowledge gaps is essential, as a conservative estimate of 6,400 kilograms of detectable PFAS enter U.S. landfills each year, an order of magnitude greater than PFAS detected in leachate. MSWLs will increasingly serve as continuous PFAS sources to waste water treatment facilities and ultimately the environment.