Distribution and bioaccumulation characteristics of emerging and legacy per- and polyfluoroalkyl substances (PFAS) in...

As replacements for legacy per- and polyfluoroalkyl substances (PFAS), perfluoroalkyl ether carboxylic and sulfonic acids (PFECAs) are increasingly applied and consequently detected in diverse environmental matrices. Yet, their occurrence and environmental behaviors in subtropical estuary-bay systems remain poorly documented. Here, we conducted a comprehensive investigation of 14 PFECAs and 22 legacy PFAS in surface seawater (N = 77), sediments (N = 29) and biota (N = 173) across a representative subtropical estuary-bay-offshore continuum. Overall, legacy PFAS dominated in seawater and biota, whereas sediments contained comparable levels of emerging and legacy PFAS owing to the elevated abundance of hexafluoropropylene oxide dimer acid (HFPO-DA). Concentrations of ∑PFAS ranged from 1.74 to 30.91 ng/L in seawater and 0.52 to 7.08 ng/g dw in sediments, indicating a relatively low contamination status compared with other Chinese coastal bays. Partitioning behavior differed substantially between chemical classes: the Kd values of hexafluoropropylene oxide derivatives (HFPOs) displayed carbon-number relationships distinct from those of perfluoroalkyl carboxylic acids (PFCAs). In biota, ∑PFAS concentrations varied from 2.22 to 65.61 ng/g dw, with perfluoro-(3,5-dioxahexanoic) acid (PFO2HxA) showing clear bioaccumulation and biomagnification potential. Notably, the relationships between bioconcentration factors of PFECAs and carbon chain length/ether oxygen content diverged from trends previously reported for Laizhou Bay, underscoring region-specific bioaccumulation behaviors. The results suggested that local residents were unlikely to experience significant exposure to PFOA or PFOS through seafood consumption. However, potential health risks associated with PFECAs remain uncertain, emphasizing the need for further evaluation of their toxicological effects.