The bioavailability processes as a key to evaluate phytoremediation efficiency

Bioavailability is the key to understanding the risks from pollution and to de-fining remediation strategies, since organisms only respond to the fraction that is biologically available. Plants are able to uptake the substances only if present in available forms in the soil environment, this means that bioavailability is the key to evaluating the feasibility of phytoextraction as a remediation technology. In soil, the bioavailable fractions of contaminants are dependent on soil prop-erties and processes. Soil characteristics are often not fully considered in the tech-nology evaluation, however the ability of the same plants to uptake metals is quite different in soils with different properties that determine metal bioavailabil-ity. Two case studies show how it is possible to increase the efficiency of phytoex-traction by manipulating the bioavailability. In the first case, the addition of vari-ous additives to a very acid soil reduced the toxic effects arising from a too high bioavailability of the metals, thus enabling the plants to grow. In the second case, the addition of a single fertilizer simultaneously increased the bioavailability of arsenic and mercury, thus promoting a greater plant uptake.