Spatial-temporal Characteristics And Evolutionary Mechanism Of Hydrogeochemistry In The Affected Area By Typical Metal Mine Tailings Ponds

In order to study the impact of tailings pond of nonferrous metal mine on groundwater environment,the concentrator of Xinxing copper mine in Urad Rear Banner was selected as the research object.There are 60 sampling points in total in 2021.Determine physicochemical properties,conventional indexes and heavy metal content,and carry out hydrogeological tests such as field drilling test,geophysical exploration test,water injection test,dispersion test,water level measurement and precipitation monitoring,as well as groundwater surface investigation,so as to obtain aquifer system structure,hydrogeological parameters and groundwater movement characteristics,Using three line diagram method,Gibbs,chlor-alkali index method,Mineral saturation index method and Ion contrast method,The sources of ions in groundwater are analyzed in detail.Spatial and temporal distribution characteristics of hydrogeochemistry revealed by Arc GIS spatial interpolation,US EPA model was used to evaluate human health risk,Evaluation of water quality based on health risk weighting method WQI.Finally,the coupling simulation model of groundwater quantity and quality is established,Predict the migration and change characteristics of major heavy metal pollutants,which provides a basis for the management of nonferrous metal mine tailings pond in northwest arid area Provide reference basis for groundwater environment restoration.（1）The source analysis of groundwater chemical components shows that the groundwater in the upper reaches of the study area is SO₄-Ca type,and gradually transits to SO4·Cl-Ca·Na·Mg type to the lower reaches.The high content of Cl^-in the Urad Rear Banner indicates that there may be class pollution in the study area.Total lead in dry season exceeds the standard,and the Serious pollution;Most samples in wet season did not exceed the standard,and only the samples in the north of the tailings pond exceeded the standard,And the concentration is higher than that in dry season.（2）Identify and evaluate the water pollution in the two periods of high and low in the study area:A comprehensive assessment of the health risks of children and adults in the tailings pond basin shows that children suffer higher cancer risk and noncarcinogenic risk.The range of high risk of carcinogenesis and high risk of non-carcinogenesis in dry season is larger than that in wet season.The high-risk areas of carcinogenesis and non-carcinogenesis in adults in dry season are distributed in blocks,mainly in the northeast of tailings pond.Children with high risk of carcinogenesis and non-carcinogenicity have a large area,which is distributed in the whole study area.The proportion of water with poor water quality in dry season is 23%,46%of the groundwater is very poor water,and the very poor water is mainly distributed near the tailings pond;In wet season,10%groundwater is poor water and 20%groundwater is very poor water,which is significantly better than that in wet season;pollution in the middle and lower reaches of the study area is higher than that in the upper reaches.（3）The hydrogeochemical reverse simulation results show that different mineral dissolution precipitations and cation exchange occur in the starting point,middle and lower reaches of the study area.In the whole process,dolomite dissolved 0.43mmol/L,calcite precipitated 0.39mmol/L,gypsum dissolved 0.39mmol/L,rock salt dissolved 2.04mmol/L,CO₂ precipitated 2.24mmol/L.A total of 1.18mmol/L sodium ions were precipitated from water and 0.59mmol/L calcium ions dissolved into groundwater during cation exchange.（4）In groundwater quantity and quality simulation,according to the temporal and spatial characteristics of hydrogeochemistry,USEPA health risk model and research results of water quality evaluation,the pollutant Pb with great harm and universality is selected as the migration simulation factor.The results show that a pollution plume with a length of about 1100m and an area of 0.24km² is formed in the study area after 3650d;With the passage of time,the pollutants that are not interfered will continue to diffuse and accumulate downstream,it will cause certain harm to the downstream water environment and ecological environment.