Investigation of Per- and Polyfluoroalkyl Substances (PFAS) Adsorption onto the Medium Size Quartz Gravel

Poly- and perfluoroalkyl substances (PFAS) are persistent chemicals that may pose risks to ecosystems and human health. Understanding the environmental fate and transport of PFAS is challenging due to their ability to migrate across air, water, and soil. In surface waters, PFAS can interact with sediments, organic matter, and plants, influencing the mobility of these compounds and posing potential risks to the environment. This study provides the first analysis of the adsorption of PFAS, including perfluoro-carboxylic acids (PFCA, C4–C10), perfluoro-sulfonic acids (PFSA, C4–C8), per-/poly-fluoroalkylether acids (PFEA C4-C8) and fluorotelomer sulfonates (FTS, C8 and C10) to medium-sized quartz gravel (pebbles), commonly found in the UK river systems. The effects of exposure time (1, 3 and 7 days) and mechanical disturbance (shaking) on PFAS adsorption were evaluated. The degree of PFAS adsorption indicated a clear dependence on the compound’s functional group and carbon chain length. Long-chain PFAS, perfluorodecanoic acid (PFDA), exhibited the highest adsorption, while PFCA showed the least sorption compared to corresponding PFEA, PFSA and FTS of homologues (C5–C8). Mechanical disturbance (shaking) of gravel in PFAS-contaminated water did not significantly influence the extent of adsorption on most of the studied analytes except 9 Cl-PF3OUdS, 8:2 FTS, and PFDA, onto the gravel. The study demonstrates, for the first time, that medium-sized quartz gravel can adsorb PFAS, including new-generation substitutes from water. In riverine systems, these pollutants can be remobilised from gravel surfaces during e.g., flooding, dredging, or changes in water chemistry, potentially reintroducing them into the water and impacting water quality and ecosystem.