In aquatic environments, heavy metals discharged from industrial or sewage effluents
or from atmospheric deposition may be rapidly removed from the water column and
transported to bottom sediment (Fo¨rstner and Wittmann, 1981; Fung and Lo, 1997).
Consequently, metal concentrations in sediment are often several orders of magnitude
higher than those in ambient seawater (Luoma, 1990).