Per- and polyfluoroalkyl substances (PFAS) in sediment: a source of PFAS to the food web?

Kent Lake is an impoundment of the Huron River in southeast lower Michigan. Fish collected from Kent Lake in 2017 had high concentrations of perfluorooctane sulfonate (PFOS) in fillets, which resulted in a fish consumption advisory from the Michigan Department of Health and Human Services. In June 2018, a major source of PFOS was identified as the City of Wixom's wastewater treatment plant, which discharges treated effluent to Norton Creek and the Huron River five miles upstream of Kent Lake. An industrial facility, which has been in operation since approximately 2000, was found to be the source of high levels of PFOS to Wixom's sanitary sewer. A granular activated carbon system was installed at the facility, resulting in substantial reductions in PFOS concentrations in surface water and fish from Kent Lake. However, the PFOS decline in fish tissue reached a plateau at a level exceeding the "Do Not Eat" advisory threshold. This case study sought to explore the supposition that sediment is acting as an ongoing source of per- and polyfluoroalkyl substances (PFAS) to the Kent Lake food web. We sampled PFAS in biota, sediment, and water from Kent Lake and a nearby reference lake in 2021. Biota (benthos, forage fish, and predator fish) were collected from both lakes and analyzed as whole-body composites for PFAS analytes. The results, including the patterns of PFAS contamination between the water, sediment, and biota samples as well as partition coefficients and bioaccumulation factors, are consistent with PFAS in sediment acting as an ongoing source of contamination to the biota in Kent Lake. This study's results for PFOS (the predominant PFAS in Kent Lake sediment and biota) and 6:2 fluorotelomer sulfonic acid (6:2 FTS) provide additional lines of evidence that sediment acts as a source of PFAS to the aquatic food web.