土壤溶质迁移过程的试验研究

Chemical Transfer From Soil into Surface Runoff

设计了自由排水、土壤水分饱和和壤中流3种水文条件,采用人工模拟5组不同地表径流流速,分别对土壤溶质迁移到地表径流过程中土壤侵蚀、伯努利效应、扩散和对流4种途径的作用机理进行了分析。结果表明,在土壤水分饱和条件下,伯努利效应引起的土壤溶质流失量占总流失量的比例很大。结合混合层理论和试验得到了3种水文条件下混合层的深度,其中自由排水（-10 cm）时混合层深度小于1.5 mm;在土壤水分饱和条件下,混合层深度介于0.9～4.5 mm;但是在壤中流条件下,混合层表现为整个土层都为混合层深度。

Although there is a conceptual understanding on processes governing chemical transport from soil to surface runoff, there are little literature and research results actually quantifying these individual processes. We developed a laboratory flow cell and experimental procedures to quantify chemical transport from soil to runoff water by each of the individual processes, i. e. , （1） erosion; （2） convention; （3） Bernoulli effect; and 4） diffusion. We imposed 3 different vertical hydraulic gradients by setting 5--flow cell to free drainage condition （-10 cm）, saturation condition and artesian seepage condition （10 cm）. Our data confirmed the general form of the convection-diffusion equation; nevertheless, we now have additional quantitative data describing the contribution from each individual chemical loading process under different surface runoff and soil hydrologic conditions. The results idehtified that Bernoulli Effect made a great contribution to transport ehemical from soil into surface runoff under saturation condition. According to our data, the mixing zone depth is gotten by mixing theories under different hydraulic gradients.