Investigating the sources of perfluorobutanesulfonic acid in a watershed of the Chugoku region in Japan

ABSTRACT Perfluorobutanesulfonic acid (PFBS), one of the per- and polyfluorinated alkyl substances (PFAS), was found in higher concentrations than other PFAS in drinking water at a drinking water treatment plant (DWTP) located in the Chugoku region, western Japan. Raw water of the DWTP is the underflow water of the Takaya River, part of the Ashida River system. In this study, surveys of 18 PFAS were conducted in the surface waters of the Ashida River system from June 2022 to June 2023 to investigate the sources of PFBS in DWTP water. PFBS was found in all samples at concentrations of 1.4–9,200 ng/L, and was widely present in the Ashida River system. Two PFBS sources were found in the tributaries of the Takaya River: the Shimizu and Miyama Rivers, involving a creek. The PFBS concentrations near the PFBS sources in the two rivers were 6,700 and 9,200 ng/L, respectively. Among the target PFAS, molar percentages of PFBS in the two PFBS sources were very high (99.6 and 79%, respectively). The estimations of PFBS loads indicated that the PFBS sources in the Shimizu and Miyama Rivers were the major PFBS sources of the DWTP, and the contribution of the Shimizu River was higher.