【摘要】 现场示踪试验和环境模拟实验是核素在地质介质迁移研究中常用的两种方法。本文同时使用上述两种方法对85Sr在黄土包气带中的迁移规律进行了试验研究。现场示踪试验在 A、B坑 (天然降水条件 )和 D、E坑 (喷淋条件 )中进行 ,模拟实验用 2号和 4号土柱作实验。试验结果表明 ,在非饱和条件下 ,黄土对 85Sr有较强的吸附能力 ,85Sr的扩散参数随时间增加而增大。试验还发现 ,85Sr在同一黄土介质中的延迟系数 Rd 并不是一个常数。由试验数据经拟合后可以看出 ,85Sr的延迟系数 Rd 随水流速度 u (亦即随土壤含水量θ )的增加而增大 ,但小于由分配系数 Kd按 Rd=(1+ρKd/θ)导出的 Rd计算值 ,并且 ,由 Kd推导出的 Rd值随土壤含水量θ变化而变化的趋势也与实测结果相反。这说明 ,在黄土包气带条件下 ,如果将Kd 当作一个常数 ,则由 Kd 推导出的 Rd 值以及由 Kd 推导 Rd 值的常用方法都是不适用的。更多还原

【Abstract】 Field tracer migration test and laboratory simulation test are two commonly used methods to study radionuclide migration in geological media. These two methods were simultaneously used to study migration of 85 Sr in loess aerated zone. The field tracer migration tests were conducted in test pits A and B (under natural rainfall condition) as well as in test pits D and E (under artificial sprinkling condition). Simulation tests were carried out in soil columns 2 # and 4 #. The results show that the loess has strong adsorption to 85 Sr and the diffusion parameter of 85 Sr increases with time under unsaturated loess. It is also found from the analyses that retardation factor, R d, of 85 Sr in the same loess is not a constant. It can be seen from the fitted results that retardation factor, R d, of 85 Sr increases with water velocity, u (i.e. water content, θ) in unsaturated loess. However, the values of R d derived from distribution coefficient, K d, obtained by batch method are higher than the measured results. Moreover, the tendency of change of R d derived from distribution coefficient, K d, with water content, θ, in loess is opposite to the measured results. It is illustrated that both the values of R d derived from distribution coefficient, K d, and the method deriving R d from distribution coefficient,K d, are not appropriate under unsaturated loess condition. (更多还原