城市地表灰尘径流冲刷过程模拟

Simulation of the dust wash-off process from impervious urban surfaces

为弥补当前描述城市地表灰尘径流冲刷过程的指数衰减模型偏于经验、物理力学机制认识不足的问题,考虑到地表灰尘的泥沙物质属性,基于泥沙科学、从泥沙运动力学角度研究地表灰尘的径流冲刷过程与模拟方法。通过比较发现,地表灰尘径流冲刷指数衰减模型与河道冲刷条件下输沙调整的滞后响应模型具有一定的相似性。基于上述比较结果,参考河道冲刷条件下输沙调整的滞后响应模型方程,针对地表径流汇流的延时效应及不平衡输沙特点,并考虑地表灰尘颗粒的非均匀性及分组冲刷过程,对地表灰尘径流冲刷指数衰减模型进行了改进,建立了地表灰尘的分组不平衡冲刷模型。结合广东东莞牛山工业园区地表灰尘径流冲刷过程的实测资料,对模型进行了应用比较。结果表明:相比指数衰减模型,分组不平衡冲刷模型模拟地表径流灰尘浓度值与实测值变化趋势更为符合,确定性系数与纳什效率系数由0.15与0.59升至0.73与0.70,模拟效果进一步提高。研究结果有助于促进地表灰尘径流冲刷过程模拟由经验分析向具有物理基础的模拟方法转变。

This paper presents a simulation method of the dust wash-off process using sediment dynamics theory to clarify the physical mechanism of the Sartor-Boyd exponential model for the dust wash-off process.Related theories including the non-equilibrium transport model for non-uniform sediment and the delayed response model for sediment transport rate during fluvial processes were summarized,and compared with the Sartor-Boyd exponential model.The comparison revealed that the Sartor-Boyd exponential model is formally equivalent to the delayed response model of sediment transport rate during the clear-water scouring process.Given the delayed effect of rainwater conflux,and the non-equilibrium wash-off characteristics of group-sized dust,a non-equilibrium wash-off model for non-uniform dust was proposed and applied to simulate the dust wash-off processes with different rainfall-runoffs in the Niushan industrial district of Dongguan City,Guangdong Province.Comparison of the application and effects indicated that the estimated dust concentration values using the proposed model were more consistent with the measured values than those calculated using the Sartor-Boyd exponential model;furthermore,the determination coefficient and Nash-Sutcliffe coefficient of efficiency increased from 0.15 to 0.73 and from 0.59 to 0.70,respectively.The results of this research provide a physical basis for the simulation of the dust wash-off process.