雨、污合流制城区降雨径流污染的迁移转化过程与来源研究

2003～2006年通过对武汉市汉阳城区不同尺度降雨径流、市政污水的监测，结合环境地球化学方法，研究雨、污合流制城区降雨径流污染的形成、迁移转化过程及污染来源.结果表明，雨、污合流制城区地表径流汇入排水系统，经排水系统传输，污染程度显著增加.屋面径流中TSS和COD浓度（EMC）的平均值分别为18.7 mg/L和37.0 mg/L，路面径流中TSS、COD浓度（EMC）的平均值分别为225.3 mg/L和176.5 mg/L，而在集水区出口处径流中TSS、COD浓度（EMC）的平均值分别为449.7 mg/L和359.9 mg/L；污染物的组成也发生了明显的改变，颗粒态COD增加了18%，有机污染增强.研究还发现，城市地表、雨水口、生活污水管和合流管道沉积物中P、Fe含量具有明显分异特征，可以利用沉积物中P/Fe识别集水区尺度降雨径流污染成因与来源.据此对集水区出口2次径流污染来源计算，56%±26%的悬浮物来自城市地表与雨水口，44%±26%的悬浮物源于生活污水的沉积物.生活污水中污染物对降雨径流污染的贡献是通过在合流管道中形成沉积发生的.雨、污合流管道在降雨径流污染形成过程中发挥了转化器和加重径流污染的作用.减少合流管道中沉积物的形成是削减径流污染负荷的途径之一.

Transport and Sources of Runoff Pollution from Urban Area with Combined Sewer System

Sampling and monitoring of runoff and sewage water in Wuhan urban area with combined sewer system were carried out during the period from 2003 to 2006, to study the transport and sources of runoff pollution at the catchment scale coupled with environmental geochemistry method. The results showed a change in quality between the runoff entering the sewer network and the combined storm water flow at the sewer's outlet. A significant increase was observed in the concentrations of total suspended solids (TSS), volatile suspended solids (VSS), COD, TN, and TP, and in the proportion of COD linked to particles. During the runoff production and transport, the concentrations of TSS and COD increased from 18.7 mg/L and 37.0 mg/L in roof runoff, to 225.3 mg/L and 176.5 mg/L in street runoff, and to 449.7 mg/L and 359.9 mg/L in combined storm water flow, respectively. The proportion of COD linked to particles was increased by 18%. In addition, the total phosphorus (P) and iron (Fe) contents in urban ground dust, storm drain sediment, sewage sewer sediment and combined sewer sediment were measured to identify the potential sources of suspended solids in the combined flow. The urban ground dust and storm drain sediment were rich in Fe, whereas the sewage sewer sediment was rich in P. The P/Fe ratios in these groups were significantly distinct and able to differentiate them. A calculation of the two storm events based on the P/Fe rations showed that 56%±26% of suspended solids in combined flow came from urban ground and storm drain. The rest were originated from the sewage sewer sediments which deposited in combined sewer on the dry weather days and were eroded on the wet weather days. The combined sewer network not only acts as a transport system, but also constitutes a physicochemical reactor that degrades the quality of urban water. Reducing the in-sewer pollution stocks would effectively control urban runoff pollution.