ABSTRACT
The degradation of soils and sediments with a number of organic and inorganic contaminants on the globe has intensi—ed during the last century as a result of a dramatically rapid increase in several anthropogenic activities, including the use of sludge or municipal compost, pesticides, fertilizers and emissions from municipal waste incinerators, car exhausts, residues from metalliferous mines, and the smelting industry. Major metals and metalloids (called trace metals, TMs hereafter), such as lead (Pb), chromium (Cr), arsenic (As), zinc (Zn), cadmium (Cd), copper (Cu), mercury (Hg), and nickel (Ni), constitute an ill-de—ned group of inorganic chemical hazards and are those most commonly found at contaminated sites. Unlike organic contaminants, which are oxidized to carbon (IV) oxide by microbial action, most TMs exhibit changes in their chemical forms (speciation) and bioavailability, but they do not undergo microbial or chemical degradation; therefore, once released, these TMs remain persistent for a long time (Adriano 2003). Therefore, worldwide soil and sediment TM contamination has raised severe concerns because of potential movement of these metals up to human food chain (Dahmani-Muller et al. 2001; McGrath et al. 2002).
