Heavy Metal Contamination of Road Dust at the Downtown Area in the Metropolitan City of Ulsan, Korea

Road dust often contains elevated concentrations of heavy metals and can influence on human health. Therefore, a study on the characteristics of heavy metals in road dust was carried out in the Metropolitan City of Ulsan of Korea. Road dust was obtained from a downtown area, Seongnamdong, Chung-gu, Ulsan. The road dust was collected inside the filter attached in the vacuum cleaner in March, 2006. The road dust was separated into four size-fractions by using the sieves as follows: 2000 mum, 850 mum, 180 mum and 75 mum. The heavy metals in road dust sample were extracted by aqua regia extraction method (HNO₃:HCl = 1:3). The concentrations of heavy metal were analyzed by atomic absorption spectrometry. The mean values in the road dust with 850 2000 mum, 180 - 850 mum, 75 - 180 mum, and < 75 mum size for Cd were 0.30, 0.46, 1.04, and 2.27 mug g^-1 , respectively; for Cu were 264.65, 139.10, 235.50, and 345.10 mug g^-1, respectively; for Pb were 51.80, 57.00, 118.40, and 223.26 mug g^-1, respectively; for Zn were 258.00, 430.05, 751.55, and 1270.85 mug g^-1, respectively; for Ni were 13.20, 24.76, 36.86, and 52.15 mug g^-1, respectively. The results indicate that the road dust in the study area has elevated concentrations of Cd, Cu, Pb, Zn, and Ni and the concentrations of heavy metals increased with the decrease of particle size. Road dust sample was also analyzed for the mobility of metals by sequential extraction methods including a modified BCR procedure and Tessier procedure. The results show that Cd was mainly in the exchangeable and carbonate phases, Ni was mainly in the exchangeable phase, Pb and Zn were associated with the carbonate fraction. However, Cu may not be associated with the exchangeable and carbonate fractions. In general, the mobility of heavy metals in the road dust might be Cd>Ni>Zn=Pb>Cu.