Distribution And Risk Assessment Of Perfluoroalkyl Substances In Lakes From The Middle Reach Of Yangtze River,China

Perfluoroalkyl substances?PFASs?are kind of new synthetic persistent organic pollutants?POPs?.PFASs have bioaccumulation,environmental persistence,long-distance migration and potential toxicity,which have long-term and potential hazards to the environment and human health.The middle reaches of the Yangtze River are important wetlands in China.Poyang Lake,Dongting Lake and Hong Lake are important lakes in those wetlands.They play a significant role in flood regulation,fishery and tourism.Furthermore,those lakes supply water for local agriculture and industry.There are only a few studies on the levels and pollution characteristics of PFASs in this area.The chemical plants,sewage treatment plants and garbage plants located in the upper reaches of Yangtze River,are the potential source of PFASs,and the high population density in large basin and human activities would strongly pose significant influence on the ecosystem of the wetland.Therefore,research on PFASs in this area is necessary.The objective of this study is to investigate the PFASs of wetlands?Dongting Lake,Hong Lake,Poyang Lake and the middle reaches?in the middle reaches of the Yangtze River.This study established two analytical methods for PFASs:gas chromatography?GC?and solid phase extraction?SPE?and high-performance liquid chromatography-tandem mass spectrometry?HPLC-MS/MS?.The HPLC-MS/MS methods were finally applied to detect 11 types of PFASs?PFBA,PFPeA,PFHxA,PFHpA,PFOA,PFNA,PFDA,PFUdA,PFDoA,PFBS,PFOS?in waterThe pollution levels,spatial distribution and environmental factors of perfluoroalkyl substances in different regions were analyzed and compared,and the ecological risk assessment to 6 typical PFASs?PFBA,PFPeA,PFHxA,PFOA,PFBS,PFOS?was operated.The mainconclusions are as follows:?1?Here we proposed a cost-effective method for the GC based determination of C4-C12 PFCAs in surface water samples by integrating solid phase extraction and PFCAs anilide derivatization.First,we assessed the performance of different PFCAs derivatization methods,namely esterification and amidation.Then the reaction conditions in the amidation approach were further optimized by usingorthogonal design experiments.After optimizing the instrumental parameters of GC,the limits of detection?LOD?of this derivatization method were determined to be 1.14-6.32 ?g l^-1.The SPE-amidation-GC method was validated for application,with good accuracy and precision reflected by the PFCAs recoveries and derivatization of triplicates.The method reported here could provide a promising and cost-effective alternative for the simultaneous determination of C4-C12 PFCAs in environmental water samples.?2?To measure typical PFASs,a method of high-performance liquid chromatography-tandem mass spectrometry was developed.The water sample was enriched and concentrated by WAX solid phase extraction column and quantitatively analyzed by isotope internal standard method.Optimization of the analytical methods of the instrument included atomization temperature,nebulizer pressure,auxiliary gas flow,capillary pressure and mass spectrometry conditions.Compared the two mobile phase elution methods,a complete detection method was established.This method has a good linear range?R²>0.99?and the detection limit is 0.005-0.023 ng l^-1?3?The results of the study on PFASs in different water sampling in the middle reaches of the Yangtze River shown that PFASs pollution is prevalent.The target pollutants of 11 PFASs were detected in 23 samples in the middle section of the Yangtze River.The total content ranged from 12.43 to 77.44 ng l^-1 with an average of 22.53 ng l^-1.Results also showed the highest concentration in Wuhan.Wuhan's fluorine chemical industry contributes a lot to PFAS emissions.The concentration of PFASs in Dongting Lake ranged from 18.07 to 29.95 ng l^-1(average concentration was 22.67 ng l^-1).the total concentration of PFASs in surface water of Poyang Lake was between 17.00 and 67.66 ng l^-1,with an average concentration of 32.29 ng l^-1.The total concentration of PFASs in Hong Lake ranged from 25.46 to 63.40 ng l^-1,with an average of 35.89 ng l^-1,which is higher than other research areas.?4?In terms of the composition of homologous substances,PFASs in the wetland of the middle reaches of the Yangtze river are dominated by short chain homologous substances,which is obviously different from the pollution characteristics of PFASs in natural water bodies dominated by PFOA and PFOS reported in the past,indicating that the short-chain substitution effect has gradually emerged in China's perfluorochemical industry.The content of PFASs varied from different areas.The PFASs in Hong Lake have the highest pollution degree,followed by Poyans Lake,Dongting Lake and the middle reaches of the Yangtze River.In general,the PFASs in the middle reaches of the Yangtze River are at a lower level.?5?Human activities,economic development levels in different region,population density,industrial density and other factors may affect the concentration level and distribution of PFASs?6?The entropy method and risk superposition model were used to evaluate the ecological risks of several typical PFASs in water bodies.Potential risks in this study areas were ranked from high to low as:Hong Lake?0.0523?>Poyang Lake?0.0392?>middle reaches of the Yangtze River?0.0228?>Dongting Lake?0.0208?,all in low-risk areas.The compounds with the highest contribution rate to RQsum were PFHxA,which contributed 52%,46%,72%and 47%,respectively,indicating that PFHxA is the main potential risk compound in this study area.