Abstract:In order to study influence of acid leaching and CO2 in-situ leaching on groundwater, quality of groundwater in Yili basin of Xinjiang was sampled and analyzed. The results show that the vast majority of component contents in groundwater is significantly higher than background value and the national quality standard of class III for groundwater in acid leaching. Total salinity is about 11 times higher than the national standard for class III groundwater. The above-standard components are sulfate, manganese, nickel, iron, lead, zinc, cadmium, arsenic and other heavy metals and radioactive elements. CO2 in-situ leaching has a much smaller effect on concentration of various components of groundwater, pH value is basically unchanged, and total salinity is about 2.6 times higher than the national quality standard of class III for groundwater. The main pollution factors in groundwater are sulfate, nitrate, chloride, manganese and nickel, while copper, zinc, cadmium, lead, iron, arsenic and other components concentration does not change significantly during CO2 in-situ leaching. Single pollution index in acid mining area is Fe>Mn>Ni>Pb>SO42->Zn>As>Cd, and single pollution index in CO2 mining area is NO3->Mn>Ni>SO42->Cl-. Comprehensive pollution index of groundwater in acid mining area is 3-384 times higher than that in CO2 mining area. Pollutants mainly come from artificially injected chemical reagents and components released by mineral reaction in ore-bearing layer. Geochemical environment and pollution characteristics of groundwater in the two in-situ leaching methods are significantly different due to different leaching agents.