基于ERT技术反演红壤剖面水分入渗过程

水分运动是土壤中物质和能量传输的主要驱动力，但是水分在土壤中的运动轨迹复杂多变，难以直接捕捉。本研究以第四纪红黏土发育的红壤为研究对象，借助电阻率成像技术（ERT），反演水分在林地和农地土壤中的入渗过程。研究发现，ERT技术能够实现水分在红壤包气带入渗过程的可视化，ERT测定的表观电阻率的变化量与烘干法测定的土壤水分之间呈极显著正相关关系（P<0.01），林地的决定系数为0.72，农地为0.53。土地利用类型影响水分入渗的范围和方式，在2 cm水头高度注水100 L的情况下，林地的入渗深度大于80 cm，而农地约为50 cm，在此基础上，继续注水200 min，林地和农地均出现明显的优先流现象。但是，林地的优先流比农地更为发育，林地是通过根系等大孔隙快速向下传输，而农地则以“指流”的方式，间断性向深层运动。在土壤层次复杂、背景含水量高、土壤黏重等不利因素的影响下，ERT技术依然能捕捉优先流在红壤中发生和发育的过程。

Inversion of Water Infiltration Processes in the Profile of Red Soil Based on ERT Technology

【Objective】 Soil moisture movement is the main driving force of the material and energy transport in soil. However, the paths of soil moisture in soils are complex and difficult to comprehend. This is especially true in the red soil region with abundant rainfall and diverse land use types.【Method】With the help of an electrical resistivity tomography (ERT), soil moisture infiltration processes in the vadose zone were captured for the forest land and farmland of the red soil from Quaternary red clay.【Result】 The results showed that in the red soil region, ERT could realize the visualization of the soil moisture infiltration process in the soil profile of the red soil. There was a highly significant correlation (P < 0.01) between the resistivity measured by ERT and the soil moisture measured by the oven drying method. The linear coefficients of determination between them were 0.72 for forest land and 0.53 for farmland. Land use types affected the mode and depth of soil moisture infiltration. With a 2-cm water head height and 100-L water injection volume, the infiltration depth of forest land was more than 80 cm, much deeper than that of farmland (50 cm). With the continued injection of water for 200 min, the infiltration depth of the two land uses exceeded 150 cm and a preferential flow phenomenon was observed during the infiltration process. However, the preferential flow of forest land was more developed than that of farmland. The preferential flow of forest land moves down rapidly through macropores formed by plant roots and soil animal activities while the preferential flow observed in farmland moved to the deep layer intermittently mostly in the way of the finger flow. In addition, the forest land was dominated by vertical infiltration with weak horizontal flow while the horizontal movement in farmland was stronger.【Conclusion】Under the influences of disadvantageous factors such as complex soil layers, high background water content and high soil clay content, ERT technology still could successfully capture the occurrence and development processes of preferential flow in red soil area.