降雨-径流条件下混合层深度模拟试验

Simulated experiment of mixing zone depth under rainfall-runoff conditions

混合层深度是非点源污染模型中一个重要参变量,在模拟土壤溶质随地表径流迁移流失过程中,它决定了参与径流迁移的土壤溶质的范围及其具体流失量,为现有模型参数校正提供一定的数据支持。通过设计3种水文条件即自由排水状态(-5cm)、土壤水分饱和状态和土壤渗流状态(5cm),采用人工模拟3种降雨强度(3,6和9cm/h),及同时分别外加模拟相对于降雨量的0,2,4和10倍径流量,研究土壤溶质迁移到地表径流过程中混合层深度。试验结果表明混合层深度与降雨强度呈线性增加关系;自由排水条件下,与地表径流量呈复杂正比例增加关系;土壤饱和条件和土壤渗流条件下,混合层深度与地表径流量均呈线性增加关系。研究结果发现混合层深度的实质是一个多向、复杂的动态溶质迁移变化量。

Mixing zone depth is an important parameter in chemical transport from soil into surface runoff,which implies chemical transport extent and loss.It provides the basic data for calibrating the model parameter.An indoor experiment was conducted to study the mixing zone depth during chemical transport from soil to runoff.Different vertical hydraulic gradients were imposed by setting the flow cell to free drainage condition（-5 cm）,saturation condition and artesian seepage conditions（5 cm） under simulated rainfall at 3,6 and 9 cm/h and simulated flow rate to rainfall at 2,4 and 10 times of simulated rainfall.Results showed that mixing zone depth increased linearly with rainfall intensity.The mixing zone depth increased inversely with runoff flow rate under free drainage condition,but increased linearly under artesian seepage conditions.Thus the mixed zone depth is a multi-directional,complex dynamic chemical transfer quantity.