山地城市暴雨径流污染特性及控制对策

为了解山城重庆的暴雨径流污染特性,充实国内仍然薄弱的基础资料,对4种用地类型的4场暴雨进行了监测,测试指标包括TSS、COD、TP、TN和NH3-N。结果表明,对于坡度2.5%的交通干道和坡度30%的校园人行道,从污染物浓度降幅的角度考虑初期径流的控制量应分别为2～3 mm和1.8 mm。随降雨时间的延长,路面污染物浓度迅速降低,坡度越大,降低速率越快。对于平均浓度,校园屋顶和草坪的各污染物浓度均达到地表水环境质量Ⅴ类标准(总氮和氨氮除外)。交通干道和校园人行道的总磷平均浓度也满足地表水环境质量Ⅴ类标准,但2种下垫面的COD、TN和氨氮平均浓度分别超出地表水环境质量Ⅴ类标准的2～8倍、1.9～3.1倍和1.9～4.3倍。对于交通干道,场次降雨径流的总氮、总磷和氨氮平均浓度与初期浓度的比值和污染物浓度20 min降幅接近(分别为0.5～0.53和50%～55%)接近,而COD和TSS平均浓度与初期浓度的比值和污染物浓度20 min降幅相近(分别为0.35～0.37和78%～84%)。对于校园人行道,污染物浓度20 min降幅均达到90%以上(90%～96%),场次降雨径流的总氮、总磷、氨氮、COD和TSS的平均浓度与初期浓度的比值接近(0.3～0.4)。研究结果为山地城市暴雨径流的污染控制提供了参考。

Characteristics and control of urban rainfall-runoff in mountainous city

In order to understand pollutant characteristics of urban storm runoff in mountainous city,and enrich basic data which was still weak in our country,four storm events were investigated and samples from four kinds of land surfaces were analyzed.The concentrations of TSS,COD,TP,TN and NH3-N were monitored.The results showed that the early 2～3 mm and 1.8 mm runoff should be controlled for traffic road with slope 2.5% and campus sidewalk with slope 30% correspondingly from the point of view of pollutant concentrations reduction.Concentrations of pollutants from road and campus sidewalk reduced quickly with the prolongation of rainfall time.The steeper the slope was,the faster the pollutant concentration reduced.With regard to the average concentration,all pollutants from campus roof and lawn met class V surface water standard except TN and NH3-N,which was the same with TP concentration from traffic road and campus pavement.However,concentrations of COD,TN and NH3-N from traffic road and campus pavement were 2～8,1.9～3.1 and 1.9～4.3 times higher than class V surface water standard respectively.As regard to runoff from traffic road,the ratio of average concentration to initial consistence of TN,TP and NH3-N and the reduction rate of pollutant concentrations after runoff occurred 20 minutes during a single rainfall event were similar to each other(i.e.,0.5～0.53 and 50%～55%),while the same property for COD and TSS were 0.35～0.37 and 78%～84%,respectively.The rate of concentration decrease for every pollutant monitored when the runoff from campus sidewalk had started for 20 minutes could all exceed 90%(i.e.,90%～96%) and the ratio of average concentration to initial consistence of all pollutants investigated was close to each other(i.e.,0.3～0.4).A reference of runoff pollution control in mountainous city was given in this study.