Abstract:

The purpose of the study is flush characteristics of urban runoff pollutant on different underlying surface. Select 5 typical hardened surfaces in Changzhou City and monitor the change process of rainfall runoff pollutant from March to August in 2015. The results showed that event mean concentrations (EMC) of pollutants in road runoff were higher than that of roof runoff. For road runoff, SS concentration was higher than the water quality standards by 1.34 times; COD concentration was higher than the water quality standards by 2.59 times. For the roof runoff, COD concentration was higher than the water quality standards by 1.8 times; and TN concentration was higher than the water quality standards by 2.6 times. For the roof runoff, the dissolved-bound fraction was 72.78% for COD, 57.99% for TN. For road runoff, the dissolved-bound fraction was 61.59% for TN. The pollutant concentrations were commonly higher at the initial stage, while decreased with prolonging of the rainfall time and gradually became stable at the later stage. The initial concentrations of pollutants from the underlying surface were as follows: concrete ground, asphalt ground, paved ground, flat roof and slope roof. During the rain flush, the concentration of pollutants on the underlying surface increases with the increase of the intensity of the rain which was fluctuated. The intensity of the first flush intensity varied by surface and was most intense for the flat roof, followed by the slope roof, then the asphalt road and finally the concrete road. Rainfall in pre-period was intensive and pollutant concentration was exponentially attenuated. When rainfall changes smoothly, the concentration of pollutants was stable firstly and then attenuation. When the rainfall was sparse in pre-period and intensive in the late-period, the curves of pollutant change type was multi-peak type. The index flush model had good effect to pollutant runoff simulation, the flush coefficients of COD on the slope roof, flat roof, and concrete road were 0.871, 0.765, and 0.025 mm⁻¹, the roof flush intensity was much larger than the ground. The flush coefficient of dissolved-bound of COD and granular-bound of COD was similar on the slope roof. The flush coefficient of granular-bound of COD was greater than the dissolved-bound of COD on the flat roof and the concrete road.

Key words: underlying surface, rainfall flush, runoff, flush coefficient

摘要：

为研究城市硬化下垫面降雨径流对污染物的冲刷特征, 选取常州市5类典型硬化下垫面, 采样监测2015年3—8月期间6场降雨径流及污染物浓度变化过程, 得到以下结果。1) 地面径流污染物EMC均值高于屋面径流; 地面径流SS和COD浓度超过水质标准Ⅴ类1.34倍和2.59倍; 屋面径流COD和TN浓度超过水质标准Ⅴ类1.8倍和 2.6倍。屋面径流中溶解态COD和TN分别占全量的72.78%和57.99%; 地面径流溶解态TN占全量的61.59%。2) 径流初期污染严重, 随着降雨过程逐渐降低, 最终趋于稳定。各下垫面污染物初期浓度从大到小依次为水泥地面、沥青地面、铺装地面、平屋面、斜屋面。冲刷过程中, 随雨强增大, 各下垫面污染物浓度升高, 呈波动式变化。各下垫面污染物均有冲刷初期效应, 下垫面初期冲刷强度从强到弱依次为平屋面、斜屋面、水泥地面和沥青地面。前期降雨强度越大, 污染物初期浓度越大, 初期效应越显著。降雨强度为大雨时, SS 浓度呈指数型衰减。降雨强度为小雨时, SS浓度先稳定, 随着降雨变密集开始逐渐减小。降雨强度为暴雨, 但降雨过程集中在中后期时, SS浓度呈先增大随后减小的趋势变化。3) 指数冲刷模型对屋面和水泥地面污染物径流冲刷模拟效果较好, 斜屋面、平屋面、水泥地面全量污染物冲刷系数分别为0.871, 0.765和0.025 mm⁻¹, 屋面冲刷强度远大于地面。斜屋面溶解态COD与颗粒态COD冲刷系数相近, 冲刷强度大。平屋面、水泥地面的颗粒态COD冲刷系数均大于溶解态COD, 颗粒态COD冲刷强度更大。

关键词: 下垫面, 降雨冲刷, 径流, 冲刷系数