Concentrations of Typical Perfluoroalkyl Acids and Contributions of Their Precursors in the Water of the Le'an River in China

Abstract

Transformation of perfluoroalkyl substance (PFASs) precursors and their contribution to PFASs pollution have become a subject of great research interest. The concentration of PFASs and their precursors and the transformation of precursors in the water samples collected from Le'an River and the effluents of sewage treatment plants (STPs) were investigated based on methods including hydroxyl radical (·OH) oxidation, extraction by solid phase, and ultra-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results of the study revealed that the PFAS concentrations were in the range of 14.89-40.84 ng·L-1and 58.63-114.87 ng·L-1, and averaged 28.76 ng·L-1 and 86.75 ng·L-1 in the water of the Le'an River and the STP effluents, respectively. The compound with the highest concentration for the two kinds of waterbodies was perfluorooctanesulfonic acid (PFOS). The PFAS concentrations showed obvious spatial differences in the water of the Le'an River. After the oxidation treatment, the PFAS concentrations clearly increased in the two kinds of waterbodies. The increased concentrations of short-chain perfluorocarboxylic acids with carbon atom numbers of 4-8 (ΣΔ［PFCAC4-C8］oxidation conversion) were higher than those of compounds with long carbon chains. However, the increased concentrations of PFCAs for the STP effluents were higher than those for the river water. The transformation ratio obtained from the increased concentration of PFCAs led by the oxidation treatment against the PFCA concentration before oxidation (ΔPFCAoxidation conversion/PFCAbefore oxidation) was lower for the STP effluents than those for the water of Le'an River, which might be induced by the precursors' degradation during the sewage treatment process.