Particle size distribution and associated pollutants in urban runoff in Zhenjiang

To elucidate the relationship of particles with varying size on the pollutants in runoff, samples of road and storm-water sediment were collected from different representative land use types in Zhenjiang in 2006. Analyses were carried out to investigate the relationship between particle size distribution and concentrations of pollutants. The results showed that, in fine weather, road sediments are mainly composed of particles with size less than 250μm. At the beginning of rainfall, particles transported with surface runoff are predominantly less than 5μm, and during rainfall, become less than 150μm, with the majority in the range of 5~40μm. Meanwhile, the concentrations of pollutants decrease gradually from the beginning of rainfall until they reach a stable value. The results of the present work describe the forms of pollutants transported in runoff and present a mechanism for transport of pollutants through analyzing the relationship between pollutants or suspended solids and particle size, therefore providing a scientific basis for management of nonpoint source pollution in a city and an alternative method for controlling such pollution.