Speciation is of the major importance to provide the qualitative information on their
reactivity under changing conditions and crucial information about ecotoxicity characteristics
(reactivity, bioavailability, toxicity) of contaminants. Speciation of the metal ions in the soil
solution may play a significant role in its bioavailability. The behavior of the elements in the
environment cannot predict on the basis of their total concentration because it overlooks the
fact that not all of the metal may be labile or available for uptake due to the different and
complex distribution patterns of metals among various chemical species of solid phases. The
total metal content of a soil is distributed among all possible chemical forms (speciation) in
the solid, liquid or the biotic phases. Use of total concentration as a criterion to assess the
potential risks may be misleading as the risks may be over-estimated, implies that all forms of
a given metal have an equal impact on the environment. Despite this, the bioavailability of
metals and the toxicity of metals are more closely related to bioavailable metal, rather than
total metal concentrations in soil. Knowing the distribution and transformation of metals
under changing condition of environment is therefore very useful to understand the processes
whereby metals are held in soil and the condition under which they can be released