The Characteristics Of Core Samples And Physicochemical Properties Of Groundwater Of A Decommissioned Area In Some In Acid In-situ Leaching Uranium Mine,Northwest,China

Acid in-situ leaching uranium mining technology is the mainstream technology of early uranium mining in china.At present,there are a number of acid in-situ leaching uranium mines in southwest and northwest that have been decommissioned or are about to be decommissioned.These acid in-situ leaching uranium mines mainly adopt sulfuric acid leaching process.After the mining area is decommissioned,the SO₄^2-concentration in the groundwater is high,the pH is low,and uranium and other heavy metals are exceeded.At present,there is no efficient,economical and environmentally friendly method for remediation of such groundwater.Therefore,studying the physicochemical characteristics of underground core samples and groundwater samples in acid in-situ leaching uranium decommissioning mining area has important guiding significance for the development of highly efficient groundwater remediation methods in acid in-situ leaching uranium decommissioning mining area.In this study,three core samples of A,B and C were taken from the same borehole with different depths in an acid in-situ leaching uranium in northwest,which analyzed by back scattered image of scanning electron microscopeh,SEM-EDS,XRD,XRF,XPS,FT-IR,microbial community diversity and five-step continuous extraction,and the physicochemical properties of groundwater in this area were analyzed.Therefore,detailed mineral composition,solid species of uranium,geochemistry characteristics,microbial diversity and physicochemical properties of groundwater were obtained.The Core samples analysis results show that it are distributed by flakes.The core samples In addition to mainly contains quartz minerals,clay minerals,muscovite and feldspar minerals,also contains a small amount of organic carbon,uranium minerals,pyrite and hematite.Quartz minerals and hematite are associated with feldspar minerals.Pyrite is distributed along the quartz margin and can be used as a interstitial material to fill in the gaps of feldspar minerals.The contents of main elements SiO₂,Al₂O₃ and K₂O are high,while the contents of trace elements are low.In the core samples,uranium may exist mainly as U?IV?and iron as Fe?III?and Fe?II?.The main solid species of uranium in core samples are carbonate binding state and residue state,followed by iron and manganese binding state and organic binding state,and the exchangeable state is basically zero.Compared with core samples of A and C,most of the uranium in core samples B can remain in the environment.Microorganisms capable of reducing U?VI?was found in three core samples A,B and C,and microorganisms capable of producing phosphatase was found in two core samples A and C.The groundwater is acidic,of which the highest concentration of SO₄^2-in the anion reaches2093.2 mg/L,the total iron concentration is 440 mg/L,Mg²⁺concentration is 143 mg/L and Ca²⁺concentration is 76.33 mg/L and the uranium concentration is 1.953 mg/L.These analysis results can provide a scientific basis for the later restoration of groundwater in acid in-situ leaching uranium decommissioning mining area.