Seasonal variation of heavy metal contents in road dust from residential, industrial and rural areas of Hong Kong

Heavy metal contents in road dust have been an important indicator of heavy metal pollution arising from traffic-related activities. In this study, 108 road dust samples were collected from four locations of Hong Kong, namely Kwai Hing (industrial area), Sau Mau Ping (residential area), Sai Kung and Tai Lam (rural area), over a one-year period and analysed for zinc (Zn), nickel (Ni), copper (Cu), lead (Pb), chromium (Cr), cadmium (Cd), and arsenic (As). The geo-accumulation indices (Igeo) and contamination factors indicated zinc, copper, chromium, to a lesser extent, nickel, and cadmium pollution of road dust in industrial and residential areas. The potential ecological risks of Cu were found to be particularly high in both areas. Residential and industrial areas are prone to considerable and very high risks, respectively, based on the risk indices (RI). The sources of heavy metals may vary slightly between the areas based on Pearson's correlation analysis. It was found that the metal contents in the road dust samples vary differently between the dry and wet seasons. The concentrations of Zn were higher in the dry season while those of Cu, Cr and Ni were generally higher in the wet season.