新疆某铀矿酸法和CO_2地浸采区地下水的污染特征及机理

为研究酸法和CO_2地浸采铀对地下水的影响,对新疆伊犁盆地的酸法和CO_2地浸采区的地下水水质进行采样分析。结果表明,酸法地浸开采时地下水中绝大部分组分含量均明显高于地下水本底值和国家地下水Ⅲ类质量标准,总矿化度超过国家地下水Ⅲ类标准11倍左右,超标的组份主要有硫酸根、锰、镍、铁、铅、锌、镉、砷等重金属元素和钍等放射性元素。CO_2地浸对地下水各个组分浓度影响要小得多,pH基本不变,总矿化度高出国家地下水Ⅲ类质量标准2.6倍左右,地下水中主要的污染因子为硫酸根离子、硝酸根离子、氯离子、锰离子和镍离子,而铜、锌、镉、铅、铁、砷等其它组分浓度未发生显著变化。酸法采区中的单项污染指数依次为FeMnNiPbSO_4~(2-)ZnAsCd,CO_2采区中单项污染指数依次为NO_3~-MnNiSO_4~(2-)Cl~-。酸法采区地下水综合污染指数比CO_2采区高3～384倍。污染物主要来源于人为注入的化学试剂和含矿层中矿物反应释放的组分,两种地浸方法由于加入的溶浸剂不同导致地下水的地球化学环境和污染特征存在显著差异。

Pollution Characteristics and Mechanism of Groundwater of Acid and CO2 In-situ Leaching Mining Area of Uranium Deposit in Xinjiang, China

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.