Heavy metal release from phosphorite tailings into seawater: a simulated laboratory study.

A number of laboratory experiments were carried out to assess the desorption of trace metals from sedimentary phosphorite samples into artificial seawater. Shaking and percolation experiments have been performed on phosphorite samples from the Cd-rich phosphorite deposits of Hahotoé-Kpogamé (Togo, West Africa) using artificial seawater in the ratio 1:10. The results show that elevated concentrations of trace elements Cd(17-256 micrograms/l), Ni (12-193 micrograms/l), Zn (21-200 micrograms/l) and major elements Al (6-1915 micrograms/l) and Fe (30-1264 micrograms/l) are released into seawater by desorption processes. Maxima of trace metals with high mobility are reached within 4 h indicating the fast desorption kinetics in seawater. Thus, the direct disposal of potentially toxic metal-rich mine tailings may lead to regional coastal water pollution.