Transport of PFAS in the Presence of Ocean Currents: Implying the Dominance of External Inputs in the Taiwan Strait

The impact of ocean dynamic processes under seasonal variations on the occurrence and transport of per- and polyfluoroalkyl substance (PFAS) in marginal seas needs more attention. Here, we investigated the distribution of 33 PFAS in surface and vertical profiles of the Taiwan Strait (TWS) during summer and autumn. The results indicated that PFAS mainly originated from exogenous inputs via seasonal currents, and industrial emissions could be their potential sources. Substantial quantities of perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA) were transported to the southern TWS by Pearl River Diluted Water (PRDW) and the South China Sea Warm Current (SCSWC) during summer. In autumn, considerable amounts of PFOA, perfluorohexanoic acid (PFHxA), and perfluorobutanesulfonic acid (PFBS) were transported to the central-northern TWS by Zhe-Min Coastal Current (ZMCC). The depth controlled by surface currents affected the vertical distribution of PFAS in shallow waters (<100 m), while the vertical variation in deep waters was caused by the intrusion of different water masses (>100 m). Risk assessment showed that areas influenced by currents had elevated risk levels. This study provides the first comprehensive characterization of seasonal PFAS dynamics in the TWS, offering valuable insights into the environmental geochemical behavior of PFAS in coastal oceans globally.