Spatiotemporal distribution, ecological risk assessment and source analysis of legacy and emerging Per- and Polyfluoroalkyl Substances in the Bohai Bay, China

The Bohai Sea is one of the most polluted hotspots by per- and Polyfluoroalkyl substances (PFASs) in the world and studies on the vertical distribution of PFASs at different water layers and phase partitioning between water and suspended particulate matter (SPM) were still limited. 23 legacy and emerging PFASs were investigated in seawater and SPM throughout the Bay in this study. The average concentrations of ∑PFASs in seawater were 48.21 ng/L and 52.71 ng/L during the periods of wet and normal water, respectively. In general, the concentrations of ∑PFASs in surface water were higher than that in deep water. Legacy PFASs in seawater were dominated by PFOA and short-chain PFASs, while the emerging alternative HFPO-DA was detected in the whole water layer of the Bohai Bay with an average concentration of 1.09 ng/L. The spatial distribution showed that ∑PFASs were higher nearshore than inside the bay and higher in the south than that in the north of the bay. The average concentration of ∑PFASs in SPM was 9.02 ng/g. Long-chain PFASs and the emerging alternative 6:2 Cl-PFESA accounted for the major contaminants. The partition coefficients log Kd and φspm-w showed a linear positive correlation with carbon chain length. Preliminary risk assessments revealed that the ecological risk of common PFASs in the Bohai Bay was low, while PFOA was at moderate risk. The principal component analysis demonstrated that the production process of traditional fluorochemical factories, fire-fighting and emerging electroplating industries were the main sources of PFASs. This was the first comprehensive survey of emerging PFASs in different water depths and in SPM of the Bohai Bay during different seasons, which provided important scientific data for studying the ecological risks and pollution prevention of PFASs.