Simulating the multi-media fate of perfluorooctane sulfonate (PFOS) and its precursors in the Bohai coastal region of China.

Abstract

PFOS and its precursors are of great concern due to their persistence and widespread presence in the environment. However, few studies have been conducted on their transformation and fate at a regional scale. We aim to address this gap by investigating their fate in the Bohai coastal region of China. Emissions of PFOS and its precursors are estimated based on anticipated POSF production in China from 1976 to 2025. Comparison of emission sources revealed that PFOS primarily originated from direct emissions, while precursors were notably influenced by indirect sources. Dynamic concentration curves of these pollutants in various compartments were simulated and validated against measured values. Spatial analysis indicated higher concentrations of these pollutants in sections 25 (Beijing), 26 (Tianjin), and 48 (Shenyang), with lower concentrations observed in sections 8, 16, and 24. The mass flux results highlighted significantly different pathways: precursors primarily interacted between upper and lower air with notable degradation, while PFOS mainly moved from lower air to soil and freshwater. Mass fluxes into the Bohai Sea suggested that PFOS mainly entered via water flow, while precursors primarily came through air deposition. Uncertainty analysis revealed higher uncertainties in soil and sediments than the oceans, with additional uncertainties in estimated emissions, and seawater salinity. This study provides a theoretical basis for modelling and regulating PFOS.