Particle size distribution and pollutant dissolution characteristics of road-deposited sediment in different land-use districts: a case study of Beijing.

The high pollutants loading of road-deposited sediment (RDS) make it the main threat to receiving water bodies in stormwater management; however, the characteristics of RDS have not yet been sufficiently studied. In this study, samples were collected from three different land-use type areas (campus, residential, and commercial) in Beijing, China, and analyzed for particle size distribution, chemical compositions, and dissolution characteristics. The results revealed that RDS in the sampling sites mainly consisted of particles < 63 μm, which accounted for 40.3%, 30.5%, and 30.3% of the total in samples from campus, residential, and commercial sites, respectively. In addition, the mass percentage of sediments decreased with increasing particle size in all three sampling sites. The highest pollutants loading were mainly found in particles between 125 and 250 μm. The pollutant loading occurred in the following order: commercial > residential > campus for COD and heavy metals (Cr, Cd, Pb, Cu), and campus > residential > commercial for TN, NH-N, and PO-P. The pollutants dissolved capacity (DC) and pollutants dissolved velocity (DV) both decreased with increasing particle size. Overall, the results of this study highlight the importance of removing fine particles to controlling road runoff pollution.