稳定塘内稻田降雨径流中氮磷输移的三维数值模拟

3D Numerical Simulation of Nitrogen and Phosphorus Transport in the Stabilization Pond of Rainfall Runoff

掌握污染物在农田排水稳定塘中的输移规律对控制农业面源污染具有重要意义.已有的研究主要集中在通过野外与室内试验监测探究稳定塘的污染物拦截效果与运行机制上,而缺乏对降雨径流过程中稳定塘内氮、磷污染物在三维空间输移的数值模拟研究.本文以多级农田排水稳定塘为研究对象,首先,对2015年水稻生长期内3场典型降雨进行了跟踪监测;然后,建立了多级稳定塘的三维水动力-水质迁移耦合模型,并应用坐标轮换法以实测数据进行了模型的参数率定;最后,对稻田降雨径流过程中稳定塘内氮磷的输移进行了三维数值模拟与模型验证,并探究了稳定塘分级数对氮磷拦截效果的影响.结果表明:率定后的模型各水质指标模拟值与实测值拟合较好;在降雨径流初期,总氮、总磷在垂向上表现为底层浓度大于表层浓度、横向上沿程浓度逐渐降低的规律;稳定塘级数的增加延长了水流停留时间,更有利于拦截氮、磷污染物.

To control the nonpoint source pollution of nitrogen(N)and phosphorus(P)in agriculture,it is significant to grasp the transport regulation of N and P in the stabilization pond.Previous research mainly focused on the N and P removal effect and running characteristics of the stabilization pond through field and laboratory monitoring,but failed to simulating the N and P transportation of the multicell stabilization pond during rainfall runoff in three-dimensional space.This paper regards the multicell stabilization pond as the case study.First,three typical rainfall runoff events were monitored during the rice-growing season in 2015.Second,a three-dimensional model coupling the hydrodynamics and water qualities of the multicell stabilization pond was established.Moreover,the parameters of the model were calibrated by the cyclic coordinate method with measured data.Finally,the calibrated model and the effect of the cell number of the stabilization pond on N and P removal were analyzed.Results show that the simulated values agreed well with the measured values after calibration.During the early stage of rainfall runoff,the concentrations of TN and TP in the lower layer are larger than those in the upper layer.Furthermore,the concentrations of TN and TP decrease gradually along the flow path.Thus,increasing the cell number of the stabilization pond is conducive to improving the effect of N and P removal.