1. Introduction
Solid wastes containing metals and other elements can be a seri- ous environmental problem. Once released, these elements may accu- mulate in soils in several different ways, as water-soluble extractable compounds or linked to carbonates, iron–manganese oxides and organic matter. The elements in the solid waste that are soluble and extractable in water are considered bioavailable and are likely to be transported to the water and, as a consequence, can be absorbed by plants and eventually can enter the food chain [1,2].