Chemical and biological parameters as tools to evaluate and improve heavy metal phytoremediation.

In this review, chemical and biological parameters are discussed that strongly influence the speciation of heavy metals, their availability to biological systems and, consequently, the possibilities to use bioremediation as a cleanup tool for heavy metal polluted sites. In order to assess heavy metal availability, a need exists for rapid, cost-effective systems that reliably predict this parameter and, based on this, the feasibility of using biological remediation techniques for site management and restoration. Special attention is paid to phytoremediation as an emerging technology for stabilization and remediation of heavy metal pollution. In order to improve phytoremediation of heavy metal polluted sites, several important points relevant to the process have to be elucidated. These include the speciation and bioavailability of the heavy metals in the soil determined by many chemical and biological parameters, the role of plant-associated soil microorganisms and fungi in phytoremediation, and the plants. Several options are described how plant-associated soil microorganisms can be used to improve heavy metal phytoremediation.