Leaching behaviour of Cd, Cu, Pb and Zn in surface soils derived from dredged sediments

Leaching of heavy metals from land-disposed dredged sediment spoils is a po tential environmental hazard. The leaching behavior of Cd, Cu, Pb and Zn in surface soils sampled from abandoned dredged sediment disposal sites was a ssessed. Using simple mass-balance calculations, the significance of the le aching test results with respect to metal migration into underlying clean s oil was appraised. The potential leachability, defined as the amounts relea sed at constant pH 4, decreased in the order (% of total contents): Zn (58% )approximate to Cd (49%) > Cu (5%)approximate to Pb (2%). The kinetics of m etal release were determined in a cascade shaking test using demineralized water acidified to pH 4 (HNO3). Metal concentrations in the leachates were low and metal migration was, assuming uniform convective flow, predicted to be of no environmental concern. It is emphasized that any long-term predic tion of metal migration is uncertain. (C) 1998 Elsevier Science Ltd. All ri ghts reserved.