Understanding the relationship between heavy metals in road-deposited sediments and washoff particles in urban stormwater using simulated rainfall

[Display omitted] ► Heavy metal concentrations in washoff particles increased by 10–30% compared with RDS. ► Rainfall intensity and duration did not affect increased rate of metal concentrations. ► Grain size of RDS and washoff particles carrying most heavy metals was different. ► Metal concentrations in RDS washoff decreased along the urban–rural gradient. Understanding the relationship between heavy metals in road-deposited sediments (RDS) and washoff particles is essential to controlling urban runoff pollution. RDS and its associated heavy metals were investigated along the urban–suburban–rural gradient around Beijing, China. RDS washoff and its associated metal contaminants in different particle size fractions were evaluated using simulated rainfall. The results showed that the washoff percentage of RDS decreased along the urban–rural gradient. The Cu, Zn, Ni, Cr and Pb contents in washoff particles were 28.1%, 20.0%, 19.7%, 11.6%, and 11.4% higher than those in RDS, respectively. Additionally, different metals showed increases in different chemical fractions. RDS particles