Per- and polyfluoroalkyl substances in Chinese and German river water – Point source- and country-specific fingerprints including unknown precursors

This study aimed at comparing source-specific fingerprints of per- and polyfluoroalkyl substances (PFASs) in river water from China and Germany, selected as countries with different histories of PFAS production. Samples were collected from up- and downstream of seven suspected point sources in autumn 2018. Amongst the 29 analyzed legacy and emerging PFASs, 24 were detected, with a sum ranging from 2.7 ng/L (Alz River) to 420,000 ng/L (Xiaoqing River). While mass flow estimates for the Xiaoqing River and Yangtze River (mean: 20 and 43 t/y, respectively) indicated ongoing high emissions of the legacy compound PFOA in China, its ether-based replacements HFPO-DA and DONA showed the highest contribution downstream of a German fluoropolymer manufacturing site (50% and 40% of ΣPFASs measured, respectively). In river water impacted by manufacturing sites for pharmaceutical and pesticide intermediates, the short-chain compound PFBS was the most prevalent substance in both countries. The German Ruhr River, receiving discharges from the electroplating industry, was characterized by the PFOS replacement 6:2 FTSA. Isomer profiling revealed a higher proportion of branched isomers in the Chinese Xi River and Xiaoqing River than in other rivers. This points to different synthesis routes and underlines the importance of differentiating between linear and branched isomers in risks assessments. Upon oxidative conversion in the total oxidizable precursor (TOP) assay, the increase of the short-chain compound PFBA was higher in German samples than in Chinese samples (88 ± 30% versus 12 ± 14%), suggesting the presence of a higher proportion of unknown precursors to PFBA in the German environment. Amongst the ether-based replacements, DONA and 6:2 Cl-PFESA were fully or partially degraded to non-targeted oxidation products, whereas HFPO-DA showed no degradation. This indicates that the inclusion of ether-based PFASs and their oxidation products in the TOP assay can help in capturing a larger amount of the unknown PFAS fraction.