BIOAVAILABILITY OF HEAVY-METALS AND DECONTAMINATION OF SOILS BY PLANTS

Bioavailability of heavy metals in metal-contaminated soils depends on physical, chemical and biological factors. Physical (structure, penet rability) and chemical factors (Eh, pH, speciation, concentration) giv e the framework in which biological factors can modify the metal avail ability by release of oxygen, protons, and organic acids and by associ ation with mycorrhizal fungi. With these conditions in mind, the possi bilities of the use of hyperaccumulating higher plants for the deconta mination of metal polluted soils, i.e. phytoremediation, are explored. By small scale experiments it has been demonstrated that at present p hytoremediation is only an economically important clean-up technique f or slightly contaminated soils. Heavily contaminated soils can only be revegetated using highly metal-resistant plants. (C) 1996 Elsevier Sc ience Ltd