Sorption: Release processes in soil-the basis of phytoremediation efficiency

The phytoremediation efficiency is influenced by contaminant bioavailability in soil, which in turn depends on soil properties. These last, together with rhizosphere processes, regulate the adsorption and release processes of heavy metals in soil. The distribution of metals between solid and liquid soil phases following adsorption/release processes determines the metal amount bioavailable for plant uptake. The use of adsorption isotherms allows evaluating this distribution, in order to describe the soil ability to retain contaminants in the solid phase. The knowledge of sorption processes is of great importance for phytoremediation, since both the specific contaminated soil and the chosen plant species can largely influence the applicability of phytoremediation procedure at field scale. A case study is reported to evaluate adsorption experiments carried out in soils derived from contaminated site with a high heterogeneity of lead concentration. Results obtained by Freundlich equation have demonstrated the possibility of correlating the desorption parameters and the quantity of elements absorbed by the plants.