土壤大孔隙发育特征对水和溶质输移的影响

Study on Developmental Characteristics of Macropores and Their Effects on Soil Water Flow and Solute Transport with Tracer Infiltration Experiments

在原状土条件下采用单离子示踪和多离子示踪技术各开展了两个入渗试验,通过对比分析试验观测结果研究了各试验区域土壤中大孔隙的存在状况、发育特征及其对入渗示踪剂溶液输移的影响。研究结果表明,试验1(单离子示踪)所在区域土壤中存在贯穿型土壤大孔隙(大孔隙贯穿整个入渗深度范围土层),试验3(多离子示踪)所在区域土壤中存在非贯穿型土壤大孔隙(大孔隙仅发生在上层部分土壤中),而试验2(单离子示踪)和试验4(多离子示踪)所在区域土壤中不存在土壤大孔隙。示踪剂溶液在含有贯穿型土壤大孔隙的试验1中运移速度更快、入渗深度更大、输移到深层土壤时的浓度更高;贯穿型土壤大孔隙对不同阶段注入的示踪剂溶液的输移能力无显著差异。与贯穿型土壤大孔隙不同,试验3中出现的非贯穿型土壤大孔隙对中间阶段(第二阶段)注入的示踪剂溶液的输移能力最大,而对第一、三阶段注入的示踪剂溶液的输移能力相对较小。

Two solo-tracer infiltration experiments and two multiple-tracer infiltration experiments were conducted in natural undisturbed soil in order to investigate the existence and penetrating depths of macropores and the effects of macropores on the infiltration of applied tracer solutions. The results revealed that full-penetrated macropores （i.e. macropores penetrated the whole infiltrated soil layer） were occurred in Plot 1 （solo-tracer infiltration experiment） and partial-penetrated macropores （i.e. macropores penetrated only part of the infiltrated soil layer） occurred in Plot 2 （multiple-tracer infiltration experiment）, while no macopores occurred in Plot 2 （solo-tracer infiltration experiment） and 4 （multiple-tracer infiltration experiment）. The tracer solution transported much more rapidly in the full-penetrated macropores to the deeper soil layer in Plot 1, and the transportability of full-penetrated macropores on applied tracer solutions did not change much with the applying sequence of tracer solutions. On the contrary, the partial-penetrated macropores in Plot 3 were much more powerful in transporting the tracer solution applied in the second step while were less powerful in transporting the tracer solutions applied in the first and third steps.