Characterizing the nature of heavy metal release reactions, sorption mechanisms, and movement in the soil is the main topic of this book. Because soils are heterogeneous, heavy metals in soils can be involved in a series of complex chemical and biological interactions including oxidation-reduction, precipitation and dissolution, volatilization, and surface and solution phase complexation. The heterogeneous nature of the different soil constituents adds to the complexity of interactions of heavy metal species with the soil environment