合流制管道沉积物中污染物的赋存特征及其季节迁移规律

Characteristics and seasonal transportations of pollutants in combined sewer sediments

沉积物是溢流污染的潜在污染来源,明确其污染物赋存特征,有助于防控溢流污染.本研究选取北京不同排水分区,分类采集了人行道步尘、机动车道街尘和合流制管道沉积物(Combined sewer sediment,CSS),监测了包括完整雨季和旱季的全年污染物变化,以探究污染物的主要来源.结果表明:CSS的污染物浓度旱季较高而雨季骤降,主要由于4月入汛期及7、8月主汛期,初次强降水径流对沉积物有较强的冲刷作用.其中,步尘、街尘和沉积物的TCOD年平均含量分别为55.37、86.42和46.43 g·kg^(-1)(以每千克TS计).非度量多维归因表明步尘和街尘是CSS的重要来源;同时,合流制管道沉积物污染物浓度显著高于分流制雨水管道,表明生活污水也是合流制管道沉积物的重要来源.此外,CSS中TCOD的含量(平均为46.43 g·kg^(-1))显著高于SCOD(平均为5.69 g·kg^(-1)),主要以非溶解态富集.研究结果可为溢流污染防控和管网运行等提供参考.

Sediment,a potential pollutant source of combined sewer overflow,which pollutants characteristics needed for management of combined sewer overflow.The work collected sidewalk dust,traffic road dust and combined sewer sediments(CSS)of different sewer systems in central Beijing,throughout wet months and dry months in a year,to trace the majority sources of pollutants.Results showed that pollutants in CSS build in dry season and flushed out in wet season rapidly,April and July and August especially,which caused by rainfall runoff of first heavy rainfall.The yearly averaged TCOD of sidewalk dusts,traffic road dusts and sewer sediments were 55.37 g·kg^(-1),86.42 g·kg^(-1)and 46.43 g·kg^(-1)respectively.Non-metric multidimensional scaling(NMDS)indicated that sidewalk dusts and traffic road dusts are significant sources of pollutants in CSS.Meanwhile,pollutants in CSS were significantly higher than in rain pipes,which demonstrated that sewage is also an important source of pollutant in CSS.Furthermore,TCOD in CSS(46.43 g·kg^(-1))was significantly higher(p<0.001)than SCOD(5.69 g·kg^(-1)),implied an enrichment of non-dissolved organic pollutants.The results provided supports for management of combined sewer overflow and sewer system.