Per- and Polyfluoroalkyl Substances (PFAS) in Urban Stormwater Runoff: Insights from a Roadside Rain Garden

Urban stormwater runoff is increasingly recognized as a critical but underexplored pathway for per- and polyfluoroalkyl substances (PFAS) to enter aquatic environments. This work investigated the occurrence and behavior of 40 PFAS compounds in stormwater runoff entering a roadside rain garden in Secaucus, New Jersey, during six storm events between August 2023 and July 2024. Total PFAS concentrations (Σ40 PFAS) ranged from 1437 to 1615 ng/L, with perfluorobutane sulfonate (PFBS, 239–303 ng/L) and perfluorohexanoic acid (PFHxA, 115–137 ng/L) consistently emerging as dominant species. Perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs) together accounted for over 70% of the total PFAS mass. Despite its intended role in water quality improvement, the rain garden showed no measurable change in PFAS concentrations (differences of only 0.03–1.10%). These findings highlight the persistence and mobility of PFAS in urban stormwater runoff and the limited efficacy of conventional green infrastructure in mitigating PFAS contamination. Furthermore, they underscore the ineffectiveness of conventional green infrastructure for PFAS mitigation and the urgent need for advanced treatment technologies integrated into urban water management frameworks.