Occurrence Characteristics Of Per-and Polyfluoroalkyl Substances In The Three Gorges Reservoir Area Leachates And YANGTZE River Water

Since the 1950 s,PFASs has been widely used in various industrial products and consumer goods due to its unique physical and chemical properties.At the same time,it is these physical and chemical characteristics that make them persistent in the environment and difficult to degrade,threatening environmental safety and human health.Most products containing PFASs will be disposed of in landfill after their lifetime.Leachate is an important medium for PFASs to enter underground and surface environments.Therefore,leachate is not only an important sink of PFASs,but also a source of secondary pollution,which deserves further attention.In addition,the daily life production,waste disposal and sewage treatment of residents along the Yangtze River in the Three Gorges Reservoir Area may cause PFASs to enter the river water,but the current research on the pollution status of PFASs in the river water of the Three Gorges Reservoir Area is limited.In order to clarify the pollution status of PFASs in leachate and river water in the Three Gorges Reservoir Area,the following studies have been carried out in this paper:(1)This is the first study to assess the pollution status and distribution characteristics of 17 PFASs in leachate samples from six municipal solid waste landfills in Western China.Based on the information of landfill site investigation and the leachate parameters,the relationship between PFASs concentration and landfill characteristics such as landfill operation time disposal capacity of landfill and leachate parameters were discussed.The results show that many kinds of PFASs can be detected in landfill leachate samples,17 PFASs concentration ranges from 1804.70 to 43309.50 ng/L(average: 14231.14 ng/L,median: 8636.01 ng/L).Compared with other studies at home and abroad,the concentrations of 17 PFASs in landfill leachate in Western China is at a moderate or high level.In addition,the main types of PFASs in landfill leachate in this study area are different from those in the eastern region(mainly PFOA),and are mainly consist of shortchain and even-chain compounds such as PFBS and PFBA.Although the factors affecting the concentration of PFASs in leachate are multivariate,it was difficult to elucidate relationships between particular landfill characteristics and PFAS concentrations.Nonetheless some statistical correlations have been found in this study,such as concentration of short-chain PFCAs is significantly positively correlated with the pH value of leachate.(2)In this study,17 PFASs(including 13 PFCAs and 4 PFSAs)were selected as the analysis objects.Firstly,the concentration level and composition characteristics of PFASs in leachate from incineration plant were investigated;secondly,the pollution characteristics of PFASs between landfill leachate and incinerator leachate were compared and analyzed;thirdly,the residual characteristics and variation rules of PFASs in leachate treatment facilities at all levels were discussed;lastly,the residual characteristics and variation rules of PFASs in leachate treatment facilities were evaluated.The potential impact of leachate treatment on the environment.The results show that PFASs widely exists in the leachate samples of incinerator and treated leachate.The concentration of 17 PFASs in the leachate of S# 1,S# 2 and S#3 in incinerator were 16565.22 ng/L,7228.09 ng/L and 9812.05 ng/L,respectively.In the same area,the composition of PFASs in incinerator leachate is similar to that of landfill leachate,and the main components are short and even chains.However,the concentration of PFASs in incinerator leachate is higher than that in "old" landfill leachate,and closer to that in "young" landfill leachate.Compared the PFASs concentration characteristics in the influent and effluent of UASB-denitrification-nitrification-UF-RO system,it was found that the system could effectively remove PFASs from leachate with removal rates ranging from 97.54% to 99.44%.Moreover,the concentration of PFASs in effluent is lower than the current international guidelines,and the impact on the environment is acceptable.Through tracing and sampling analysis of effluent from different structures,it can be inferred that the decrease of PFASs concentration in water phase during the whole treatment process may be mainly due to physical interception or sedimentation,resulting in the removal of PFASs adsorbed in suspended particles or sludge.(3)In this study,water samples were collected from 34 sampling sites in the Three Gorges Reservoir during the impoundment period(October 2018)and the sluicing period(April 2019),and 68 samples were obtained.17 PFASs were analyzed and detected for the first time.The results show that PFASs is ubiquitous in the Three Gorges Reservoir.During the impoundment period,the concentration of PFASs ranges from 50.42 ng/L to 145.59 ng/L,and the main compounds are PFPeA(mean value: 16.62%),PFHxA(mean: 17.35%)and PFHpA(mean: 19.81%).While in the sluicing period,and the concentration range of PFASs was 1.40-38.62 ng/L,and the main compound was PFOA(mean: 66.69%).There are significant differences in PFASs concentration and composition between impoundment and sluicing periods.From the spatial distribution trend,the concentration of PFASs increases gradually from upstream to downstream in impoundment period,while the sluicing period is just the opposite.This may be due to the change of water flow velocity in the reservoir area caused by the operation of the dam,the slow flow velocity near the dam during the storage period,the weakening of the diffusion capacity of PFASs,and the easy accumulation.