非均匀流动示踪试验及活动性流场模型的应用

TRACER EXPERIMENT AND APPLICATION OF ACTIVE REGION MODEL FOR HETEROGENEOUS SOIL WATER FLOW

采用显色和离子示踪方法,研究水流运动和溶质迁移非均匀特性,并分析活动性流场模型(ARM)描述水流运动和溶质迁移的有效性。运用碘-淀粉显色方法观测水流非均匀流动模式,用溴、氯和硝酸根三种离子示踪水流的非均匀运动特性。ARM耦合非均匀流动所具有的分形特性,该模型本构关系参数反映活动性流场面积比例和土壤水有效饱和度之间的分形关系。与连续性模型相比,ARM模拟土壤水流和溶质迁移结果与测定值更符合。在水平剖面三种离子浓度均表现出正态或对数正态分布规律,且总体上分布离散程度表现出随深度增加而减小的趋势,ARM有效地描述了非均匀流动下水流运动和溶质迁移所表现出的宏观特性。

A field experiment that combined iodide-starch staining with conservative ions as water flow tracers were conducted to investigate the heterogeneity of water flow and solute transport. The active region model （ARM） was applied to characterize heterogeneous water flow and solute transport iodide-starch staining and distributions of Br^- , Cl^- and NO3^- in soils. Heterogeneous flow patterns were visualized from the tracers. The ARM described the fractal characteristics of the heterogeneous water flow. A relationship between the proportion of active region within the whole region and the effective saturation of soil water was established with a power function, in which the power was related to the fractal dimension. Results indicated that simulations of water flow and solute transport using the ARM matched the measured data better than those using the continuum model. The results also showed that the concentration distributions of the ion tracers were normal or lognormal distributions and the dispersion degree of solute concentrations decreased with soil depth. Based on the analyses, it was concluded that the ARM was useful to characterize the macroscopic features of heterogeneous water flow and solute transport in soils.