Per- and polyfluorinated alkyl substances (PFAS) in the Scheldt Estuary: Insights from target, suspect and non-target screening of water, sediment and bivalves

Per- and polyfluoroalkyl substances (PFAS) are a concern due to their persistence and widespread environmental distribution. This study analysed PFAS in water, sediment, and bivalves (resident blue mussels and translocated Asian clams) along the Scheldt Estuary (the Netherlands-Belgium) using target, suspect screening (SS), and non-target analysis (NTA). As a result, various PFAS, including ultra-short-, short-, and long-chain PFAS, were detected in varying concentrations. Targeted analysis detected 8 PFAS in water (∑PFAS: 9.4-585 ng/L), 11 PFAS in sediment (∑PFAS: 7.5-47.8 ng/g dw), and 8 PFAS in bivalves (∑PFAS: 1.8-17.5 ng/g ww). SS and NTA detected 7 to 9 additional PFAS in each matrix, with estimated ∑PFAS concentrations ranging from 883 to 6421 ng/L in water, 49 to 110 ng/g dw in sediment, and 42 to 111 ng/g ww in bivalves. Short-chain PFAS dominated the relative contributions to ∑concentrations in each matrix. The Environmental Quality Standard (EQS) for perfluorooctanesulfonate (PFOS) in surface water (0.65 ng/L) was exceeded at most locations, while in bivalves it remained below the biota EQS of 9.1 ng/g ww at all sites. Estimated ∑PFAS concentrations based on SS and NTA generally exceeded results from targeted analysis in each matrix, emphasizing the importance of untargeted methods for comprehensive PFAS monitoring and risk assessments. Notably, trifluoromethanesulfonic acid (TFMS) dominated at an industrial estuary reach, while several precursors were tentatively annotated. Multivariate analyses indicated inverse correlations between bivalve-sediment ∑PFAS and positive sediment PFAS correlations with TOC and clay, indicating sorption-limited bioavailability. While this study provides valuable insights on the distribution of PFAS in estuarine ecosystems, future studies should consider suspended particulate matter and tidal cycles to better understand the environmental fate of these contaminants.