城市降雨屋面、路面径流水文水质特征研究

为研究城市硬质下垫面径流的水文过程与污染物浓度变化特征,对北京市2006年6-8月的4场降雨进行路面和屋面水文、水质过程同步分析.结果表明,径流曲线与降雨过程线形状类似,波动幅度相对较小,滞后于降雨过程线5～20 min,屋面径流系数在0.80～0.98之间;路面径流系数在0.87～0.97之间.径流污染物的浓度是由累积排放规律决定的,路面径流的污染物浓度高于屋面径流,径流中COD、TN、TP的浓度均超过地表水环境质量标准V类水要求.各类污染物之间的相关性均处于显著性水平R=0.1以上,屋面径流颗粒物与有机物和阴离子之间的相关关系较大(＞0.5),而与氮磷等营养物质的相关系数较小(＜0.5);路面径流中,TN、1P与颗粒物的相关性有所增加.径流中各类物质大多存在初期冲刷现象,并受到污染物种类、下垫面特征、降雨强度和雨型等因素的影响.SS初期冲刷现象较其它几类污染物更为明显,路面较屋面更容易形成初期冲刷,低强度降雨不容易形成有机物和营养物质的初期冲刷现象.控制初期径流污染是北京市径流管理的有效措施.

Hydrology and Pollution Characteristics of Urban Runoff: Beijing as a Sample

The purpose of this study is identification and characterization of hydrological process of urban runoff, as well as concentration variation of pollutants in it. Samples were collected in 4 rainfall events in Beijing from Jun. 2006 to Aug. 2006. Hydrology and pollution of the rainfall-runoff process were analyzed on roof and road. Study results show that the shapes of hydrological curves of runoff, despite for a 5min~20min delay and a milder tendency, are similar to rainfall curves. Runoff coefficients of roof are 0.80~0.98, while 0.87~0.97 of road. Event Mean Concentrations (EMC) of pollutants are influenced by build-up and wash-off features, which lead to a higher concentration in road runoff than in roof runoff. Major pollutants that excess the water quality standards are COD, TN, and TP. Evident correlations (>0.1) are found between pollutants. Correlation with particles are higher for COD and SO42- (>0.5), while lower for nutrients (<0.5). First Flush Effects (FFE) are found and affected by several factors; such as pollutant variety, types of land covers, and rainfall intensity. FFE are found more intense in SS, more frequently in road runoff, and more difficult to form for COD and nutrients with low rainfall intensity. Therefore, control of first period of runoff would be an effective approach for runoff management in Beijing.