Basic study on pollutant movement in an unsaturated zone considering stagnant.

为了评价污染物在非饱和带中的运动，对各种土壤进行了示踪试验。研究强调了由于土壤的非均匀性，孔隙区存在滞流区，结果表明，孔隙区滞流区对污染物运移有一定的影响。在饱和条件下，移动的区与停滞区的比值估计为10^<-1>，而在非饱和条件下，该比值估计为10^<-3>~ 10^<-2>。由于数值模拟采用解析解较好地拟合了溶质在非饱和带中的运移规律，因此，基于停滞区概念的四参数模型是合理的，实验结果也考虑了非均匀性。即使对于实验的空间尺度，10 μ m<-2>至10 μ <-1>m，也认识到了异质性。原状土的非均质性大于扰动土。在评价包气带中污染物运移时应考虑滞流区的存在.考虑滞流效应的对流扩散方程能较好地模拟污染物在包气带中的运移.由于非均匀性在实验室规模上得到了认可，因此在今后的分析中，除了考虑停滞效应外，还需要考虑非均匀性的模型。

To evaluate pollutant movement in an unsaturated zone, tracer tests were carried out for various soils. This research emphasizes the existence of stagnant region in porous zone due to heterogeneity of soils.Results show that there is effect of stagnant region in porous zones on pollutant movement. Ratio of the mobile region to the stagnant region was estimated as magnitude 10^<-1> for saturated condition, while that was from 10^<-3> to 10^<-2> for the unsaturated condition. Since solute movement in unsaturated zone was well fitted by the numerical simulation using tlte analytical solution, the four parameter model due to the concept of stagnant region is enough reasonable.The heterogeneity was also considered for the experimental results. Even for the spatial scale of the experiments, 10^<-2> to l0^<-1> m, the heterogeneity was recognized. Heterogeneity of undisturbed soil was larger than that of disturbed one.The conclusion is :1. We should consider the existence of stagnant region for evaluation of pollutant movement in unsaturated zone.2. The Convection Dispersion Equation considering stagnant effect works well for the evaluation of pollutants movement in unsaturated zone.3. Since heterogeneity was recognized for laboratory experimental scale, the model considering heterogeneity in addition to stagnant effect is necessary for analyses in the future.