降雨—径流作用下红壤坡面侵蚀过程及溶质迁移特征

发布时间：2018-07-11 12:40

本文选题：模拟降雨 + 放水冲刷　；参考：《华中农业大学》2015年硕士论文

【摘要】：南方红壤丘陵区气候温和,雨量丰富,是我国水热条件较好、占地面积较大,是我国重要的粮食生产区,对我国农业经济发展起关键性作用。随着经济发展,过度的人为活动使该区森林和地表植被大面积破坏,加之该区地形复杂,降雨强度大且集中,水土流失比较严重,致使该区土层薄化,岩石裸露,耕地面积锐减,耕地质量下降,农业生产全面衰退。同时土壤中大量的农药和养分随着径流泥沙流入河流、湖泊、水库等,使水体受到严重污染。因此,开展南方红壤区土壤侵蚀机理及养分迁移机制研究,保护红壤资源迫在眉睫。本研究结果可为红壤区防治水土流失、改善生态环境及发展农业生产提供依据。本文基于室内模拟降雨试验和径流冲刷试验相结合的研究方法,选择非吸附性Br-作为示踪剂,研究了雨滴打击、径流冲刷、降雨-径流组合作用这三种侵蚀动力下坡面红壤侵蚀过程和养分迁移规律,评价了降雨-径流不同作用机制对坡面产流产沙的影响,揭示了坡面产流产沙的水动力学机理及坡面径流溶质溴的迁移机制,阐明了坡面土壤侵蚀过程及溶质迁移特征。主要结论如下：(1)雨滴打击对坡面侵蚀过程及溶质流失的影响模拟降雨条件下,雨强对坡面产流产沙速率影响显著,雨强越大,产流、产沙速率越大。产流、产沙速率和径流含沙量随降雨时间的持续呈现阶段性变化趋势,其中累计径流量和累计泥沙量均与产流历时呈较好的线性关系,累计径流量与累计泥沙量之间呈现显著的幂函数相关关系；产流初始6 min是径流溶质流失的主要阶段,相同降雨历时下径流溶质Br-流失量表现为：120 mm/h 90 mm/h 60 mm/h。(2)径流冲刷对坡面侵蚀过程及溶质流失的影响模拟径流冲刷条件下,不同流量下坡面侵蚀产沙呈现不同的变化趋势,其中低流量下(10L/min)侵蚀泥沙变化平缓,高流量下(15L/min、20L/min)侵蚀泥沙主要集中在最初5 min。溶质流失主要集中在最初5 min,占总量的40%以上。累计径流量与产流历时呈现显著的正线性相关关系,累计泥沙量与产流历时、累计径流量间均呈现幂函数关系；径流溶质Br-浓度随产流历时呈现幂函数递减规律。(3)降雨-径流共同作用对坡面侵蚀过程及溶质流失的影响降雨和放水冲刷共同作用下,降雨强度和上方来水流量对产流产沙动态变化曲线影响较小,产流产沙速率随产流时间总体呈减小趋势,产沙速率衰减速度比产流速率快。累计径流量与产流历时呈线性关系,而累计泥沙量与产流历时、累计径流量间呈幂函数关系。径流溶质Br-浓度与产流时间呈幂函数关系。降雨-径流共同作用下,坡面水流流态主要以紊流、急流为主,阻力系数(f)与雷诺数(Re)之间呈现很好的幂相关关系。通过通径分析与相关分析得出,雷诺数是影响土壤坡面侵蚀的主要水力学参数。径流剪切力、水流功率和单位水流功率三个水动力学参数均是描述径流平均输沙率、径流溶质流失率的良好指标。
[Abstract]:The southern red soil hilly region has a mild climate and abundant rainfall, which is the most important grain production area in our country. It plays a key role in the development of our country's agricultural economy. With the economic development, excessive human activities make the forest and surface vegetation in the area damaged in large area, and the terrain is complex and rainfall intensity in this area. Large and concentrated soil erosion is serious, resulting in the thinning of soil layer, bare rock, the sharp decrease of cultivated land area, the decline of cultivated land quality, and the overall decline of agricultural production. At the same time, a large amount of pesticides and nutrients in the soil flow into rivers, lakes and reservoirs, so that the water is seriously polluted. Therefore, the soil erosive machine in the red soil region of the south is carried out. This study can provide a basis for the prevention and control of soil erosion, the improvement of the ecological environment and the development of agricultural production in the red soil region. Based on the study method combined with simulated rainfall experiment and runoff scour test, this paper selected non adsorptive Br- as a tracer and studied the rain drop. The erosion process and the rule of nutrient migration in the red soil of the slope surface of the three kinds of erosion power, such as strike, runoff scouring and rainfall runoff combination, were used to evaluate the effect of rainfall runoff different mechanism on runoff and sediment yield on slope surface. The main conclusions are as follows: (1) the influence of raindrop on the process of slope erosion and the loss of solute in the simulated rainfall conditions, the rainfall intensity has a significant effect on the rate of runoff and sediment yield on the slope, the greater the intensity of rain, the greater the runoff yield, the greater the rate of sediment yield. There is a good linear relationship between cumulative runoff and accumulated sediment volume, which shows a significant power function relationship between cumulative runoff and accumulated sediment; the initial 6 min of runoff is the main stage of runoff solute loss, and the loss of solute Br- in the same rainfall duration is 120 mm/h 90 mm/h 6. The effect of 0 mm/h. (2) runoff erosion on the erosion process and solute loss of the slope surface under simulated runoff erosion conditions, the erosion and sediment yield of the slope surface under different flow rates showed a different trend, of which the erosion sediment was slow under low flow rate (10L/min), and the high flow (15L/min, 20L/min) erosion sediment mainly concentrated on the initial 5 min. solute loss. The initial 5 min, accounting for more than 40% of the total amount, has a significant positive linear correlation between the cumulative runoff and the duration of runoff. The cumulative sediment volume and the runoff time, the cumulative runoff has a power function relationship, and the concentration of the runoff solute Br- presents a power function decreasing rule with the runoff. (3) the rainfall runoff joint action on the slope erosion process and The effect of rainfall and water discharge scour on the loss of solute is less affected by rainfall intensity and water flow rate on the dynamic change curve of runoff and sediment yield. The rate of runoff and sediment yield decreases with the flow time, and the rate of sediment yield is faster than the rate of flow rate. The cumulative runoff is linear with the duration of runoff, and the accumulated sediment is accumulated. The relationship between cumulative runoff and runoff is a power function relationship. The relationship between the concentration of Br- and the time of runoff is a power function relationship. Under the joint action of rainfall runoff, the flow patterns in the slope are mainly turbulent and jet flow, and the resistance coefficient (f) and Reynolds number (Re) show a good power correlation. Renault through path analysis and correlation analysis Number is the main hydraulic parameter that affects soil slope erosion. The runoff shear force, water power and unit flow power are three hydrodynamic parameters which are good indexes to describe runoff average sediment transport rate and runoff solute loss rate.
【学位授予单位】：华中农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S157

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