野外非饱和土壤水流运动速度的空间变异性及其对溶质运移的影响

根据野外非饱和溶质运移试验资料,分析了港质运移速度的空间变异性,求得了呈对数正态分布的流速分布函数,并依此推导出有效弥散系数α=0.068t.根据流速的随机分布特征,分别用带有随机参数的对流模型、对流一弥散模型和传统的对流-弥散模型,求得了区域平均浓度分布及其方差.计算结果与实测结果拟合良好.通过分析得到,浓度方差与浓度梯度成正比,与孔隙弥散系数成反比,方差最大值分布在浓度锋面附近.

Velocity Spatial Variability and its Effect on Solute Transport in Field Unsaturated Soil

In this paper, the spatial variability of solute transport velocity is analyzed based on the unsaturated solute transport experiment in a field. The lognormal distribution function of the velocity and then the effective dispersivity are obtained. The mean concentration and variance are calculated by using convective equation and convective-dispersive equation with the resulted stochastic velocity and the classical convective-dispersive equation. The calculated result is in fairly agreement with the experimental data. It is shown that the concentration variance is proportional to concentration gradient and inverse proportional to the local dispersivitv. The maximum concentration variance is near the concentration front.