Competitive adsorption of heavy metals in soil underlying an infiltration facility installed in an urban area

摘要

Accumulation of heavy metals at elevated concentration and potential of considerable amount ofnthe accumulated heavy metals to reach the soil system was observed from earlier studies innsoakaways sediments within an infiltration facility in Tokyo, Japan. In order to understand thencompetitive adsorption behaviour of heavy metals Zn, Ni and Cu in soil, competitive batchnadsorption experiments were carried out using single metal and binary metal combinations onnsoil samples representative of underlying soil and surface soil at the site. Speciation analysis ofnthe adsorbed metals was carried out through BCR sequential extraction method. Among thenmetals, Cu was not affected by competition while Zn and Ni were affected by competition ofncoexisting metals. The parameters of fitted ‘Freundlich’ and ‘Langmuir’ isotherms indicated morenintense competition in underlying soil compared to surface soil for adsorption of Zn and Ni. Thenspeciation of adsorbed metals revealed less selectivity of Zn and Ni to soil organic matter, whilendominance of organic bound fraction was observed for Cu, especially in organic rich surface soil.nCompared to underlying soil, the surface soil is expected to provide greater adsorption to heavynmetals as well as provide greater stability to adsorbed metals, especially for Cu.