Study On The Chemical Characteristics And Origin Of Deep Groundwater In Beishan High Radioactivity Waste Geological Disposal Pre-selection Area And Its Adjacent Area

Beishan area of Gansu Province is the first choice for geological disposal of high-level radioactive waste in China.The predecessors have done a more in-depth study on the geological and hydrogeological conditions of this area,and even have made some breakthroughs.However,the research on the chemical characteristics and genesis of deep groundwater is mainly limited to the Beishan pre selection area,and the research on the relationship between groundwater in the Qilian Mountain Hexi Corridor in the South and Ejinaqi in the northeast is]incomprehensive.Therefore,based on the subject of"Research on the chemical characteristics of groundwater and the genesis of deep groundwater in the key areas of Beishan pre concentration area"(No.21104001100),this paper systematically carried out the research on the hydrogeochemical characteristics and the formation mechanism of deep groundwater in the key areas of Beishan pre concentration area and its adjacent areas.The research results are of great significance to the evaluation of the safety of Beishan high-level radioactive waste repository.Based on the hydrogeochemical and isotopic characteristics of groundwater in the three groundwater systems of the north foot of Qilian Mountain Hexi Corridor,Beishan Mountain and Heihe River,through hydrogeochemical investigation and hydrogeochemical simulation of water rock interaction,the hydrogeochemical,hydrogen oxygen,Sr and rare gas isotopic characteristics of groundwater in the study area are determined,and the study area is established The age of groundwater is measured,the recharge elevation of deep groundwater is calculated,and the genetic mechanism of deep groundwater is discussed.The results show that the atmospheric draw Line equation and isotope elevation effect equation are?D=7.71?18O+8.71,?¹⁸O=-0.00558H+7.30 and?D=-0.04476H+66.68,respectively.The type of deep groundwater in the clastic sedimentary rock aquifer in the northern Qilian Mountain Hexi corridor area is SO₄·Cl-Mg·Ca or SO₄·Cl-Na·Mg·Ca.The recharge sources are atmospheric precipitation,melting water of ice and snow in Qilian Mountain and shallow groundwater.The recharge elevation is 2385?3274 m,and the average age of ¹⁴C is 7250a.The type of groundwater in the deep part of granite fracture in Beishan groundwater system is mainly Cl·SO₄-Na.Its supply source is shallow groundwater in Western yinaoxia area,and it may also be supplied by deep groundwater in Huahai area in the north of Hexi corridor.The supply elevation is lower than 2385?3274 m,and the average age of ¹⁴C is 11672a.The chemical types of the deep groundwater buried in the thick alluvial and proluvial aquifer of Heihe groundwater system are SO₄·Cl-Na,SO₄-Na·Mg and SO₄·Cl·HCO₃-Na·Mg.The recharge sources are atmospheric precipitation and shallow groundwater.The recharge elevation is 2443?3091 m,and the ¹⁴C age is 3107?35505a.From the perspective of groundwater chemistry,isotopic geochemistry and hydrogeochemistry simulation,this paper expounds the hydrochemistry and isotopic geochemistry characteristics of groundwater in Qilian Mountain Hexi Corridor,Beishan area and Heihe River Basin,determines the groundwater recharge elevation and groundwater age in Beishan,and reveals that the groundwater in Beishan granite is mainly from the West The formation mechanism of shallow groundwater recharge in the area of Yinaoxia.These results can provide a scientific basis for the safety evaluation of the geological repository of high-level radioactive waste in the Beishan pre concentration area.