[Sedimentation Characteristics and Pollutant Content Distribution of Storm Drainage Sediments]

To determine the characteristics of precipitation and pollutant content in storm drainage sediments, samples of sediment from building areas (including residential areas), roads, and green spaces in Wuhan were collected and analyzed. The settling velocity results show that particles with high settling velocity weight occupied a larger proportion in the sediment; the settling velocity distribution of sediments in building areas and roads was more stable than that in green spaces; and the proportion of particles with settling velocity over 3.00 cm·s^-1 in building areas, roads, and green spaces decreased in turn. The particle size distribution indicated sediment size had a wide variation range, with most particles concentrated in the range 13-628 μm, and that the particle size distribution in sediment from the same land type could differ greatly. Each sample was divided into seven groups according to settling velocity. The contents of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) were tested. The results indicate that pollutant contents in groups containing particles with settling velocity over 3.00 cm·s^-1 or below 0.025 cm·s^-1 were lower than those in other groups. Most pollutants were concentrated in particles with high settling velocity.The COD concentration declined in green spaces, roads, and building areas, in turn, for most cases. The nitrogen content in the drainage sediment of roads was lower than those in the two other kinds of land, whereas the phosphorus content in the drainage sediment of building areas was higher than those in the two other kinds of land. In the storm drainage sediment, the ratio of COD:TN was between (51-89):1 and that of COD:TP was between (102-186):1.