In order to clarify the hydrochemical characteristics of groundwater in Yingjun No.3 well field in Inner Mongolia, reveal the water quality status, formation mechanism and hydrogeological laws, and provide scientific support for the formulation of mine water prevention and control measures and the sustainable utilization of groundwater resources, this paper systematically studied the main ion composition, total dissolved solids, total hardness, pH value and other core parameters and hydrochemical type characteristics of each aquifer by collecting groundwater samples from the Cenozoic loose aquifer, Cretaceous pore fissure aquifer and Jurassic Zhiluo Formation sandstone fissure aquifer in the well field, combined with hydrochemical index detection, statistical analysis and Piper three-line diagram visualization method. The results showed that except for HCO3-, the contents of other ions and total dissolved solids increased significantly with the increase of aquifer depth. The water quality of the Cenozoic loose aquifer was the best and the runoff conditions were the best. The total dissolved solids of the Jurassic Zhiluo Formation sandstone aquifer were the highest ( average 3069.00 mg/L ), and the water quality was relatively poor. The hydrochemical types of each aquifer are mainly SO4·Cl-Na type and SO4·Cl-Na type, reflecting that most of the aquifers have hydraulic connections, and the local connection is weak due to the influence of structure or aquiclude thickness. The difference of hydrochemical characteristics is mainly controlled by geological background, water-rock interaction and runoff alternation conditions.
