土壤性质对入渗再分布影响的显色示踪试验研究

Experimental Study on Effects of Soil Properties on Infiltration Redistribution Using Combined Tracers of Dye and Iodine

同时使用染色剂和碘离子作为示踪剂,染色剂用于示踪大孔隙通道,根据碘-淀粉显色反应确定实际流动模式。开展了6组试验,研究了土壤大孔隙特征和非均匀流动特性,比较了粉土和粘土2种土壤,入渗水量分别为20、40、60和80 mm以及不同流动边界条件下的土壤水和溶质再分布特性。实验资料显示,入渗水再分布主要受到湿润模式的影响。入渗水量较小的情况下,水流运动主要发生在大孔隙中,随着入渗水量增大,入渗模式与孔隙发育表现出显著的区别,随着入渗水量的增加,水流运动非均匀性表现出先增加,随后减小的趋势。溶质迁移非均匀性取决于水流非均匀流动特性,然而表现出更多的不确定性。

Totally 6 infiltration experiments were performed in the field,including various boundary conditions（i.e.,the initial ponding depths on the soil surface： 20,40,60,and 80 mm）,different soil texture（i.e.,the silt and the clay） and different hydraulic boundaries（i.e.ponding boundary and flux boundary）.The dye photographs provided visualization of the macropores.An iodine-starch staining method was applied to visualize flow paths in the soils.Results showed that the redistribution of infiltration water was mainly attributed to the wetting patterns.The actual flow patterns showed obviously difference with the dye stained patterns as more water infiltrated into soil.Applied water depth affected flow patterns in various ways.With small applied water depth the water was quickly absorbed by soil and restricted to form preferential flow patterns,resulting in relatively homogeneous flow patterns.When the applied water depth continued to increase,flow paths were fully expanded and united,resulting in less heterogeneous flow patterns.Solute transport processes were more heterogeneous than the water flow processes.Compared with soil water flow,solute transport process was more uncertain.