The speciations of heavy metals (Cu, Zn, Pb, Cd and Cr) in bottom sediment soils collected from Kusaki dam-lake in Gunma Prefecture were considered to be in the solubility with the type of ligands, by a sequential extraction procedure with five fractionations. Through these procedures, a large amount of Cu in Kusaki dam-lake sediment was in a fraction bound to organic matter ; those of Zn and Pb were in an oxide fraction bound to iron and manganese oxides, and those of Cd and Cr were in the exchangeable fraction and in the residual fraction, respectively. The composition of species in a heavy metal was almost the same without any regard to the collection periods for two and a half years, the particle size of the sediment soils and the collection points. The total concentrations of heavy metals in the sediment soil at Kusaki dam-lake was still high at this stage, compared with those at Kanto loam and Black soil (Kurobokudo). From the distributions of each fraction for analyte heavy metals, the ratios of heavy metals with long-term leaching were estimated.
