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利用自制的设备,采用水平土柱吸渗法,测定了不同参数土壤中铀溶液的质量浓度,通过Fick扩散第二定律推导的公式计算其扩散系数。并对比氯离子迁移试验,探讨了时间、距离、土质、孔隙度等对铀扩散的影响,进而研究尾矿库中核素U(Ⅵ)的运移扩散规律。结果表明:铀和氯离子在砂质土壤中的扩散均比在黏质土壤中快,氯离子在黏土中的扩散系数D=0.354×10~(-3)m~3/d,在砂土中的扩散系数D=1.830×10~(-3)m~3/d,铀在黏土的扩散系数D=0.950×10~(-3)m~3/d,在砂土中的扩散系数D=1.623×10~(-3)m~3/d;铀在土壤中的质量浓度随扩散时间延长逐渐增大,且与扩散距离呈比例关系;铀在土壤中的扩散系数随土壤孔隙度增大而变大。
The self-made equipment was used to measure the mass concentration of uranium solution in soils with horizontal soil column suction method. The diffusion coefficient was calculated by the formula derived from the second law of Fick diffusion. The effects of time, distance, soil quality, porosity and so on on the diffusion of uranium were discussed, and the transport and diffusion of the radionuclide U (Ⅵ) in the tailings reservoir were studied. The results show that the diffusion of uranium and chloride ions in sandy soil is faster than in clayey soils, and the diffusion coefficient of chloride ion in clay is 0.354 × 10 -3 m 3 / d. The diffusion coefficient D = 1.830 × 10 ~ (-3) m ~ 3 / d, the diffusivity of uranium in clay D = 0.950 × 10 -3 m -3 / d, the diffusion coefficient D in sand = 1.623 × 10 ~ (-3) m ~ 3 / d. The mass concentration of uranium in soil gradually increases with the extension of diffusion time and is proportional to the diffusion distance. The diffusion coefficient of uranium in soil increases with the increase of soil porosity Large and large.