Abstract:Based on monitoring and analysis of 14 rainfall-runoff events on Lukou overpass of Nanjing Airport Expressway, the effluent regularity, event mean concentration (EMC) and occurrence percentage of both solution-state and granular-state COD in runoff, as well as their influential factors were explored. With large initial rainfall intensity, the scouring action was evident and the effluent COD was dominated by granular state and then by solution state in the later stage, while with small initial rainfall intensity, the solution effect was evident and the effluent COD was dominated by solution state. In terms of the median EMC in the runoff of the 14 rainfall events, the granular-state COD was around 2 times as high as the solution-state COD. The descending order for influence weights of rainfall characters on granular-state COD was as follows: antecedent days of dry weather > maximum rainfall intensity > rainall volume and durtion of rainfall. The descending order for influence weights of rainfall characters on solution-state COD was as follows: maximum rainfall intensity > durtion of rainfall and rainfall volume > antecedent days of dry weather.