Research On Chemical Characteristics And Health Risk Assessment Of Groundwater In Eastern Henan Plain

The water-rock interaction in the process of groundwater formation and the influence of human activities will make its composition change correspondingly,which will have a certain impact on the individuals who drink groundwater.Based on the eastern plain as the research area,in the area of groundwater chemical characteristics,formation mechanism and health risk assessment research,the main research results are as follows:（1）Inverse distance weighting method and hydrochemical analysis method were used to study the spatial and temporal distribution characteristics of chemical components of groundwater in the study area during 2019-2020.In 2020,the shallow groundwater in the study area is dominated by weakly alkaline fresh water and brackish water,the main anions are HCO₃^-,Na⁺and Mg²⁺,and the main hydrochemical type is HCO₃-Na·Mg water.The middle and deep groundwater is mainly weakly alkaline brackish water,and the main anions are HCO₃^-and Na⁺,and the main hydrochemical types are HCO₃-Na type water.Compared with 2019,the main anions and hydrochemical types in groundwater in the study area in 2020 were consistent with those in 2019.The concentrations of p H,TDS,Mg²⁺,Na⁺and HCO₃^-in shallow groundwater showed an increasing trend on the whole.The concentrations of Ca²⁺,SO₄^2-and Cl^-showed a decreasing trend on the whole.（2）In shallow groundwater of the study area in 2020,Cl^-and HCO₃^-were strongly positively correlated with Na⁺,Mg²⁺,Na⁺,SO₄^2-and Cl^-were highly positively correlated with TDS,and SO₄^2-was highly positively correlated with Cl^-.In the middle and deep groundwater,Na⁺,SO₄^2-and Cl^-are highly positively correlated with TDS,Ca²⁺is highly positively correlated with Mg²⁺,Na⁺and Cl^-are highly positively correlated with SO₄^2-,and Cl^-and HCO₃^-are strongly positively correlated with Na⁺.In deep groundwater,SO₄^2-and Cl^-are highly positively correlated with TDS,Ca²⁺is highly positively correlated with Mg²⁺,and Cl^-is highly positively correlated with SO₄^2-.The chemical composition of groundwater in the study area is mainly affected by rock weathering.Calcite and dolomite are supersaturated,and rock salt and gypsum are not saturated.The results of reverse hydrogeochemical simulation show that dolomite,gypsum,halite,illite,kaolinite,fluorite and CO₂ are mainly dissolved and precipitated along the simulated paths of middle and deep groundwater,accompanied by cation exchange.（3）The high fluorine groundwater is widely distributed in the eastern Henan Plain.The excessive fluorine content in shallow groundwater accounts for 69.7%of the total area,and the average fluorine concentration is 1.15mg/L.The area with excessive fluorine content in middle and deep groundwater accounted for 81.6%of the total area,and the average fluorine concentration was 1.33 mg/L.The dissolution of fluorite in shallow and middle deep groundwater in the study area did not reach saturation state,and the precipitation of calcite controlled the increase of Ca²⁺concentration.The adsorbed Na⁺in the water-bearing medium continued to exchange Ca²⁺in the groundwater,leading to further enrichment of fluorine in the groundwater.The formation of high fluoride groundwater in the study area is mainly related to weak alkaline water,cation exchange,fluorite dissolution and calcite precipitation.（4）According to Brown water quality evaluation results,the proportion of excellent,good,medium,poor and extremely poor groundwater quality in 2020 in the study area is 22.79%,38.34%,28.49%,8.83%and 1.55%,respectively.The middle and deep groundwater were 17.24%,75.87%,6.89%,0%and 0%,respectively.Deep groundwater was 8.33%,50%,41.67%,0%and 0%,respectively.On the whole,the groundwater quality in the study area is good,but the concentration of F^-exceeds the standard obviously,which has an adverse effect on the water quality evaluation results.The non-carcinogenic health risks（HQ）of F^-to different populations in the groundwater of the study area were:adult female,adult male and children from small to large.On the whole,the non-carcinogenic health risk of groundwater in the study area was higher,which corresponded to the high concentration of F^- in groundwater.