地下水中酸性污染羽的自然净化作用数值模拟研究

摘要

In-situ leaching uranium mining using acid solutions has a great impact on groundwater environment, leaving acid plumes in groundwater after mining activities.Effective measures should be taken to restore the water quality in mining aquifers.Natural attenuation is an economical method.But the effectiveness should be evaluated before using this remediation method.In this study,natural attenuation of an acid plume in a shutdown uranium site is simulated using reactive transport modeling method.PHT3D is used to construct the model,including advective-dispersive transport,aqueous speciation of 12 components,and precipitation-dissolution of six minerals.The model has a whole simulation time of 5 years.Simulation results show that:successive pH buffer reactions with calcite, Al(OH)3(a)and Fe(OH)3(a)create distinct geochemical zones.With the high pH environmental downstream, concentration of SO2-4 decreases significantly related to calcite dissolution and gypsum precipitation reactions.Most metal ion contaminants also have an attenuation process.%酸法地浸采铀对铀矿层的地下水环境有极大的破坏作用，当开采结束后将形成酸性地下水污染羽。为恢复含矿含水层的水质，必须采取有效的污染治理措施。自然净化是一种较经济的方法，但是必须对其有效性进行评价。本研究以某退役地浸铀矿采区含矿含水层为研究对象，采用反应溶质运移模拟方法来研究酸性污染羽在含水层中的自然净化作用。研究中使用PHT3D模型模拟污染羽的运移，模拟反应组分共12种、沉淀-溶解矿物共6种，模拟时长为5a。模拟结果表明：酸性污染物进入地下水后，形成了由方解石、Al（OH）3（a）和 Fe（OH）3（a）反应所控制的pH缓冲区；随着酸性污染羽的向下游高pH值地下水区域移动，方解石溶解与石膏沉淀反应可使SO2-4浓度产生明显下降，其他主要金属离子污染物也有明显的自净作用。