Abstract: Increasing urban development in China has caused increasingly serious heavy metal pollution in urban runoff. Road-deposited sediment (RDS) is an important carrier of heavy metals. In this study, we selected the urban-rural fringe of Beijing as the research area to evaluate the pollution load and assess the health risk of heavy metals (As, Cd, Cr, Cu, Mn, Pb, Zn). The results showed that the average concentrations of As, Cd, Cr, Cu, Pb and Zn, except Mn, had exceeded the background values. The mean concentration of Cd was 3 times the background value, and the mean concentration of Cr was 4 times the background value. Under runoff scouring, the pollution load of Cr was 34 times that of other metals, the highest in all study areas. Exposure model calculation showed that the average daily non-carcinogenic exposure values of heavy metals for three exposure pathways followed the order of ingestion > dermal contact > inhalation. Thus ingestion is the main exposure pathway. We detected non-carcinogenic risk for children in the area around the intersection of Luqiu and Huang Goose Road, and low non-carcinogenic risk for adults in the whole area. We found relatively low carcinogenic risk in each study area, as the areas total carcinogenic risk of heavy metal contamination via respiratory exposure pathways was lower than the environmental safety threshold.

Key words: road-deposited sediment, heavy metal, runoff, pollution load, health risk assessment