Abstract:In this paper, the groundwater in the decommissioned mining area of an in-situ leaching uranium mine in Northwest China is selected as the research object. Through field investigation and sampling analysis, the content of uranium and other physical and chemical properties in groundwater are studied. The geochemical model PHREEQC is used to calculate the given form of uranium in the water environment of this area, and the influence of uranium form under different pH, temperature, SO42- concentration and NO3- concentration is simulated by changing the simulation conditions. The results show that the valence state of uranium in groundwater in this area is nearly 100% U(Ⅵ), and its forms mainly exist in the forms of UO2SO4, UO22+, UO2(SO4)22- and UO2NO3+, accounting for 72.0%, 20.7%, 7.2% and 0.1% respectively. The simulation results show that when pH=2~5, UO2SO4 has always been the dominant species state in the water environment. With the continuous increase of pH value, UO2(OH)2 increases significantly and becomes the dominant species state after pH=5; When the temperature is in the range of 10~40℃, UO2SO4 is always the dominant species in the water environment. With the increase of temperature, the content of UO2SO4 also increases slowly; With the decrease of SO42- concentration, UO2SO4 will decrease. When the SO42- concentration is as low as 0.005 mol/L, UO22+ becomes the dominant species; With the decrease of NO3- concentration, UO2NO3+ will decrease slowly, but the dominant species state is still UO2SO4.