UNDERSTANDING FATE AND TRANSPORT OF PERFLUOROOCTANE SULFONIC ACID (PFOS) WITHIN RIPARIAN FLOODPLAINS

Understanding the fate and transport of PFAS compounds is quite challenging as their behavior is controlled by the characteristics of the adsorbent, adsorbate, and aqueous solution. Our goal was to understand how sediment heterogeneity alter the flow and sorption behavior of PFAS in the riparian floodplains. We present results of extensive field and laboratory experiments at the Theis Environmental Monitoring and Modeling Site in Southwest OH combined with numerical simulations to understand the fate and transport of perfluorooctane sulfonic acid (PFOS) during river stage fluctuation events. Our results show that the exchange of river water and PFOS through heterogeneous sediments increases with higher conductive sediment fraction, as such facies types become connected. This increases both total amount of PFOS in the aqueous phase as well as sorbed at air-water interfaces (AWIs). Sorption at sediment interfaces is more complex with a 50% sand-fraction displaying the highest levels of sorption indicating a complementary relationship of sand connectivity and sorption sites in the silt. Higher and lower sand fractions display lower solid-phase sorption due to either and a lack of sorption sites or a lack of hydraulic conductivity, respectively. Our results suggest that accurate characterization of sedimentary architecture and sorption characteristics of an aquifer system leads to an improved understanding of the fate and transport of PFOS in the hyporheic zone.