Uncovering the effects of the North Pacific Subtropical Gyre on per- and polyfluoroalkyl substances distribution in the Tropical Western Pacific.

The accumulation of per- and polyfluoroalkyl substances (PFAS) in subtropical gyres, commonly referred to as "garbage patches", remains insufficiently characterized. In this study, we collected surface seawater samples from 40 sites across the Tropical Western Pacific (TWP) and identified 19 different PFAS. Of them, perfluoro-n-butanoic acid (PFBA) exhibits the highest concentration (median 329.2 pg/L). The concentration of ΣPFAS in nearshore region (median 910.5 pg/L) is higher than those in two other oceanic regions (with medians of 773.8 pg/L in Philippine Sea and 863.1 pg/L in Equatorial Current, respectively). However, in North Pacific Subtropical Gyre (NPSG), the ΣPFAS concentration (median 1056.5 pg/L) is higher than that in the nearshore region and significantly higher than in North Equatorial Current (NEC) (p < 0.05) and the composition and concentrations of PFAS in this region significantly differ from those in other oceanic regions (p < 0.05). Additionally, PFBA, an alternative perfluoroalkyl carboxylic acid (PFCA), is significantly enriched in the NPSG (p < 0.05). These suggest that alternative PFAS have now become the main PFAS pollutants in the surface waters of TWP, with PFOA and its alternatives making up the majority. Enrichment of PFCA is observed in the surface seawater of NPSG, with enrichment factors influenced by chain length and human activities. This study provides the first comprehensive analysis of the distribution and migration characteristics of PFAS in TWP, emphasizing the influence of subtropical gyre on PFAS accumulation.