Leaching Characteristics of Heavy Metals in Road Dust in Tokyo

Leaching tests on road dust are necessary to clarify the transport of heavy metals in water cycle in urban areas. In this study, leaching tests were conducted to evaluate the leaching characteristics of heavy metals from road dust in a heavy-traffic area and in a residential area. The results show that the leached concentrations of Cr, Fe, Ni and Cu from road dust in the heavy-traffic area were significantly higher than those from road dust in the residential area. Additionally, the leached fractions of Cr from road dust in the heavy-traffic area were also significantly larger than those from road dust in the residential area. The leached fractions of Cr from road dust seem to be derived from traffic sign markers such as yellow paint. Leaching tests on size-fractionated road dust revealed that the leached concentrations of Al, Cr, Cu, As and Cd were higher in their fine fractions (< 106 μm), whereas the leached concentrations of Mn, Zn and Pb were higher in their coarse fractions (106∼2000 μm). There were different tendencies in leaching characteristics from fine to coarse fractions among the heavy metals.