331 / 2024-09-14 11:49:09

Spatial distribution, historical dynamics, and ecological risk of per- and polyfluoroalkyl substances (PFAS) in subtropical estuarine sediments: Insights into chlorinated polyfluoroalkyl ether sulfonate transformation

Cl-PFESA,F-53B,H-PFESA,PFECHS,temporal trend,sediment core

Per- and polyfluoroalkyl substances (PFAS) are synthetic long-lasting chemicals widely used in industrial and consumer products. Marine sediment is a major repository for PFAS in the environment; accordingly, this work investigated 45 legacy and emerging PFAS in samples of surface sediments and sediment cores (1940s−2020s) collected in the Pearl River outlets, its estuary, and the adjacent northern South China Sea (NSCS), one of the global pollution hotspots. The range of total PFAS concentrations in surface sediments from the river outlets and the NSCS was 244−14400 pg/g dry weight (dw) and 31.6−363 pg/g dw, respectively. Perfluorooctane sulfonate (PFOS) concentrations exhibited a decreasing trend after 2016, reflecting the effectiveness of China’s restriction on PFOS since 2014. Levels of long-chain perfluorinated carboxylates have been increasing since the 1980s and experienced an accelerated rise in the 2000s, aligning with the timeline of PFAS regulations in developed countries, reflecting the PFAS industry shifts to China in the early 2000s. Hydrogen-substituted polyfluoroalkyl ether sulfonate (H-PFESA), a less studied emerging PFAS, was widely found in the sediment samples. The ratios of 6:2 H-PFESA to 6:2 chlorinated (Cl-) PFESA in sediment cores exceeded those in surface sediment and exhibited an increasing trend with the sediment age, indicating the gradual transformation of 6:2 Cl-PFESA to its hydrogen-substituted analog in sediments. 6:2 PFESAs and PFOS were predicted to pose medium to high risks to benthos inhabiting the NSCS, while the risk brought by PFOA was generally low.