干裂作用下农田径流与溶质迁移机理研究

The existing research results show that the farmland soil desiccation crack holds an important position in terms of preferential flow in soils, solute transportation and environmental pollutant migration. Through the direct and indirect experimental methods, the project researches the quantitative evaluation index of farmland soil desiccation crack, reveals its morphological structure and space variation law, establishes and simulates a random network model. In view of the cracks closure caused by soil water expansion, the project studies the impact between soil moisture and solute transportation, surface runoff and soil solute dissolution process respectively through a network of soil cracks, then builds the three areas of soil crack network, soil matrix and farmland surface runoff and solute transportation coupled model, finally reveals the farmland runoff and solute transportation mechanism under the action of soil desiccation crack. The findings will improve the understanding of farmland water movement and solute transportation law and have a significant application value for the guidance of agricultural irrigation and the improvement of agricultural water efficiency.

已有结果表明农田土壤干缩裂隙在土壤优先流、溶质运移和环境污染物的迁移方面具有重要地位。本项目通过直接与间接的实验方法,研究农田土壤干缩裂隙的量化评价指标，揭示其形态结构及空间变化规律，并建立随机网络模型模拟验证；通过土壤裂隙网络分别对土壤水分与溶质运移、地表径流与土壤溶质溶出过程影响研究，构建土壤裂隙网络、土壤基质与农地地表水流与溶质迁移三区耦合模型，从而最终揭示土壤干缩裂隙作用下农田径流与溶质迁移机理。研究结果将提高对农田水分运动以及溶质运移规律的认识，对于指导农业灌溉，提高农业用水效率有着重要的应用价值。

已有结果表明农田土壤干缩裂隙在土壤优先流、溶质运移和环境污染物的迁移方面具有重要地位。本项目通过田间试验与模型模拟的研究方法，对农田土壤裂隙演化试验图像进行二值化、去除噪点、提取裂隙边缘等处理，并应用闵科夫斯基函数定量分析裂隙形态变化，揭示了农田土壤表面干缩裂隙发展规律以及形成机理，建立了基于胡克定律的土壤干缩开裂模型。开展了不同降雨条件下裂隙存在试验组与裂隙不存在试验组显色示踪试验，利用图像二值化分析了裂隙存在试验组与裂隙不存在试验组土壤水分入渗、溶质运移、地表径流规律特性，通过田间模拟实验，建立了全耦合（地表-基质-裂隙）模型并进行模型验证，建立了土壤基质水流运动方程和三维土壤裂隙网络区水流运动方程耦合。研究结果提高了对农田水分运动以及溶质运移规律的认识，对于指导农业灌溉，提高农业用水效率有着重要的应用价值。