Pollution characteristics and phase partitioning of per- and polyfluoroalkyl substances in Tiaozini tidal flat wetland, Dongtai

Perfluoroalkyl substances (PFASs) are a family of emerging pollutants of greatest concern. However, few studies on PFASs in protection zone of tidal flat wetland have been reported in China. Seawater and sediment samples from twelve stations in study area were collected in winter and summer to study the occurrence, spatial and temporal distribution and phase partition of 26 typically legacy and emerging PFASs. The results showed that the total concentrations of PFASs in seawater ranged from 7.95—54.52 ng·L−1. PFOA and PFHxA were the two predominant PFASs in seawater, and their mean concentrations were 10.87 ng·L−1 and 5.63 ng·L−1. The total concentrations of PFASs in sediment ranged from 0.44—1.99 ng·g−1 dw. PFBA and PFOA were the two predominant PFASs in sediment, and their mean concentrations were 0.34 ng·g−1 dw and 0.20 ng·g−1 dw. Emerging replacement surfactants for PFOA and PFOS, HFPO-DA and 6:2 Cl-PFESA were extensively detected in Tiaozini tidal flat wetland with detection frequencies 100%. The PFASs concentration of seawater in summer was higher than in winter, which is opposite to their seasonal variation trend in sediment, may be attributed to seasonal rainfall and environmental change in tidal flat. The high concentration of PFASs were found at stations near the estuary, indicating that terrigenous inputs and human activities have a significant impact on the distribution of PFASs in Tiaozini tidal flat. The phase partition of PFASs between water and sediment was associated with the carbon chain length, structure of functional group and physicochemical property of PFASs. Long chain PFASs tend to absorb onto sediment than short chain homologs. PFSAs adsorbed on sediments more easily than PFCAs with the same carbon chain length. The lgKd values of HFPO-DA and 6:2 Cl-PFESA were comparable to the lgKd values of PFOA and PFOS, with the similar phase apportion performance and therefore requires continuous attention.