Particle size distribution and total suspended solid concentrations in urban surface runoff

An in-depth understanding of particle size distribution as well as total suspended solids (TSS) in surface runoff is essential for managing urban diffuse pollution. In this study, field experiments and model simulation were undertaken to explore and confirm the dynamic runoff behaviour of TSS and their influencing factors. Field observation results showed that samples with high TSS concentrations contained coarser particles (>100 mu m) during three natural rainfall events. Particle size distribution as well as road-deposited sediments (RDS) amount before and after these rainfall events also confirmed that a higher percentage of washed-off coarser particles resulted in higher TSS concentrations in surface runoff water. The impacts of rainfall characteristics, urban-rural gradients, surface roughness, and climate difference on particle distribution as well as TSS concentration were analyzed using the wash-off formula of particle size. These factors mainly affected the contribution rate of RDS to TSS by altering particle size composition; rates ranged from 4% to 44% under different rainfall characteristics. The critical particle size (<100 mu m) was developed according to the mass percentage of particles with different sizes in RDS and TSS. Our results can provide a simple and effective way of assessing RDS contribution to TSS in surface runoff.

Automated summary

An in-depth understanding of particle size distribution and total suspended solids (TSS) in surface runoff is crucial for managing urban diffuse pollution. Field experiments and model simulation were used to explore the dynamic behavior of TSS and influencing factors, showing that higher TSS concentrations in surface runoff contained coarser particles washed off from road-deposited sediments. Factors such as rainfall characteristics, urban-rural gradients, surface roughness, and climate differences affect the contribution rate of RDS to TSS by altering particle size composition.