Per- and Polyfluoroalkyl Substance Release from Aqueous Film-Forming Foam Impacted Solids Exposed to Stormwater and Saltwater

Abstract

Saltwater intrusion is an emerging threat to coastal communities and infrastructure, including Superfund and Department of Defense sites. Per- and polyfluoroalkyl substances (PFAS) are frequently detected at these sites but our understanding of the effect of saltwater on solids containing sorbed PFAS on the transport of these compounds is limited. In this research, we applied synthetic stormwater and saltwater to aqueous film-forming foam (AFFF)-contaminated aquifer solids in saturated column experiments. The columns enabled us to compare the effects of salinity on the elution of perfluorooctanoate, perfluorooctanesulfonate, and two six-carbon zwitterionic polyfluorinated compounds found in AFFF. Perfluoroalkyl carboxylate anions at environmentally relevant pH values experienced a faster release regardless of the water matrix salinity. Our results indicate saltwater slowed down the release of zwitterionic PFAS with terminal negative charges but accelerated the release of zwitterionic PFAS with terminal positive charges. We also observed that saltwater caused preferential release of branched PFAS. Our findings have implications for site management of PFAS in AFFF source zones and their resiliency to saltwater intrusion from land subsidence, increased groundwater pumping, and future climate-driven sea level rise threats.