Study On Leaching Characteristics And Numerical Simulation Of Uranium In Shallow Soil Of Tailings Reservoir

At present,the nuclide migration in soil has caused serious pollution to the environment.In order to help the treatment of soil pollution,it is necessary to study the characteristics of the nuclide leaching in the soil.In this paper,taking the shallow soil of a large tailings reservoir in Hunan Province as the research object,taking the nuclide uranium as an example,the dynamic soil column leaching experiment under simulated rainfall conditions and the numerical simulation analysis based on Geostudio software are used to draw the following conclusions:(1)Through the physical and chemical testing of soil samples,it is concluded that the shallow soil in the tailings reservoir area is silty clay,the soil is acidic,the main chemical components in the soil are Si O2 and Al2O3,and the nuclide uranium in the soil is far exceeding the national soil environment background value of 2.8 mg/kg.(2)Through the soil column leaching experiment,it is concluded that the p H value of the soil column permeation is slower than before,and that the p H value of the leachate gradually decreases at the later stage.The volume of permeable fluid at the bottom of the column first increased and then decreased,and finally reached a stable trend.The uranium concentration in the seepage solution at the bottom of the soil column is slightly higher than that in the middle.The change of uranium concentration in the soil column exudates first and then decreases rapidly,and finally remains stable.With the decrease of p H value,the amount of uranium in soil increased.(3)Through Geostudio software numerical simulation,the soil water characteristic curve and permeability coefficient curve of soil samples are obtained.On the ninetieth day,the moisture content of soil at different heights was balanced and the soil was completely saturated.The migration distance of uranium in a single convective condition is shorter for 600 days.It is deduced that the diffusion of uranium is mainly dependent on the diffusion of hydrodynamics and the diffusion of molecules in the soil with small permeability.(4)The concentration of uranium in soil column soil decreases from top to bottom,and the velocity of concentration gradient changes faster before 90 days,and the velocity of concentration change decreases after 90 days.(5)Through the comparison of Geostudio software numerical simulation results and experimental results,it is proved that the software can better simulate the leaching and migration of heavy metals in soil,and can provide prediction for the migration of environmental pollutants.