Phyto-remediation of soils infested with radionuclides and heavy metals

Environmental pollution can be defined as the direct or indirect impairment of the environment suitability for supporting life due to harmful concentration of materials, whether or not toxic materials. Thus, a very high concentration of a nutrient might be polluting, whereas a deadly poison in great dilution is not. Earlier in this century, wastes could be discharged into the environment with relative impurity. Two factors have changed this. One is the population growth. The other factor is the rapid advance of technology which has enhanced the production of toxic pollutants. Unlike biological wastes, the wastes resulting from mining, processing of raw materials and manufacturing are often highly toxic. Heavy metals like Pb, Cd, As, Zn, Cr, Cu and radionuclides may damage especially the soils in the experimental military area. Passive bioaccumulation is based on bioabsorption and biostopping. Phyto-remediation is based on the capacity of some plants to absorb radionuclides and heavy metals from the soil. This process may be active or passive and now it may be done with genetic engineering help. Phytoextraction consists in using plants to absorb toxic metals from soils collecting parts in radices, leaves, flowers and fruits. Radices filtration is based on radices property, which grows in well-aired water from precipitations and concentrates toxic metal by phytovolatilisation. Phytovolatilisation is based on extraction of heavy metals from soil by plants and evaporation at the level of leaves. (author)