Hydrochemical Evolution And Health Risk Assessment Of Groundwater In Fen River Basin

The Fen River is the second largest tributary of the Yellow River.It flows through many urban clusters such as Taiyuan and Linfen in its basin,with a large population.Groundwater is an important source of water for local residents.understanding the evolution,pollution status,and health risks of groundwater is essential for the sustainable utilization of water resources.This study focuses on the Fen River Basin and collects 111 sets of surface water and groundwater samples to determine their physical and chemical parameters,major ions,trace elements,and stable isotopes.The hydrochemical and stable isotope characteristics of the groundwater in the study area were analyzed,and studied their spatial and temporal variations.The chemical evolution of groundwater was explored from three driving forces:natural processes,human activities,and geological conditions.Groundwater quality and human health risk assessments were also conducted.The results show that:The groundwater has successively experienced the water type evolution process of HCO₃·Ca-Mg,SO₄-Cl·Ca-Mg,HCO₃-Cl·Na along the flow direction.Dissolution-precipitation,cation exchange and dedolomitization cause the content of main cations in groundwater change regularly;manure,sewage and agricultural fertilization jointly affect the content of NO₃^-in water.Nitrification and denitrification have a certain regulatory effect on NO₃^-.Coal mining activities have caused a large amount of SO₄^2-to entering the groundwater.The occurrence of evaporation affects the content of TDS in water.Water rock interaction,dedolomitization,cation exchange,evaporation and precipitation collectively control the hydrochemical evolution process of groundwater.The unique mountain-canyon-basin topography creates very complex geological conditions and has a significant controlling effect on the hydrochemical evolution.The hydrochemical evolution rules at the edge,central and discharge areas of the Taiyuan basin are completely different,which are controlled respectively by mixing,water-rock interaction,dedolomitization,cation exchange and evaporation.Xiwenzhuang uplift on the east side of the basin led to the mixing of sulfate-type karst water and ancient water into the groundwater aquifer,resulting in the salinization of groundwater in the central part of the basin and accumulation of sulfate-type groundwater in the southern drainage area.The elevation differences in the upstream mountain area and Linghuo canyon is obvious,the groundwater flows rapidly,resulting in shorter periods of water-rock interaction,and the main evolution processes is dedolomitization and cation exchange.The hydrochemical evolution of groundwater in Linfen basin is mainly characterized by dedolomitization and cation exchange.Mining activities have a certain control over the chemical composition and type of groundwater.The mountains extending in the central part of the basin have led to the accumulation of groundwater,and introduced the lateral recharge of mountains to mix with it.Additionally,long-term groundwater accumulation also strengthens evaporation.EWQI water quality assessment results of shallow groundwater in Fen River Basin range from 10.39 to 1329.51,and the overall water quality is poor.Taiyuan basin and Linfen basin are the main areas with poor water quality.The quality of shallow groundwater in the basin has improved in the rainy season.The evaluation results of irrigation water quality shows that some shallow groundwater used for irrigation may cause salt damage,which affects the normal metabolism of plants and thus endangers plant growth.As,F,NO₃^-and Cr in the shallow groundwater of the basin cause obvious health risks,which F having a higher non-carcinogenic risk and Cr having a higher carcinogenic risk.Oral intake is the main route of exposure,with little intake through skin absorption.The seasonal variation of the health risks that different pollutants may cause to human body is relatively obvious.It can be seen that the non-carcinogenic risk of children in rainy and dry seasons is higher than that of adults.The research results contribute to understand the hydrochemical characteristics and evolution of groundwater in the Fen River Basin,and effectively identify the control effect of complex terrain structure on it.On this basis,water quality assessment and human health risk assessment have been carried out,providing a basis for the effective management and utilization of groundwater,pollution identification and pollution prevention.