Leachability of per- and poly-fluoroalkyl substances from contaminated concrete

The historical use and storage of aqueous film-forming foams (AFFF) containing per- and poly-fluoroalkyl substances (PFAS) at a range of sites including airports, defence, and port facilities have resulted in a legacy of contaminated infrastructure such as concrete. Contaminated concrete constitutes an ongoing source of PFAS contamination requiring management to ensure the protection of human health and the environment. In this study, modified Leaching Environmental Assessment Framework (LEAF) and Australian Standard Leaching Procedure (ASLP) were used to examine the leachability of PFAS, specifically, perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonate (PFHxS) and perfluorohexanoic acid (PFHxA) from AFFF-contaminated concrete collected from an Australian Defence Fire Training Area (FTA). In general, PFAS readily leached from intact contaminated concrete monoliths with the cumulative proportion (%) decreasing in the order: PFHxA (>95%) > PFOS (26-84%) ≈ PFHxS (14-78%) > PFOA (<1-54%). Higher leachability for PFHxA from concrete is consistent with previous findings for solids, however, inconsistent for PFOA with higher retention (lower leachability) in concrete as compared to PFOS. Duration of exposure to water (0.5-48 h) and temperature (25 °C and 50 °C) had little influence on the proportion of PFAS leachability from powdered concrete. A higher proportion of PFAS leached from a <2 mm concrete powder size fraction as compared to 2-20 mm and 20 mm size fractions. This behavior reflects an increase in surface area with decreasing concrete particle size. Reducing the particle size could enhance PFAS removal from waste concrete.