Radionuclides differences from metal pollutants

One of the most relevant environmental consequences of the existence of colloids derives from their ability to adsorb different species and to exchange ions. Examples include radionuclides, organics, and metal derivatives that may be toxic pollutants. Colloids that retain these species may participate in transforming them into catalysts, after which they transport them into aqueous systems located far from their original discharge points. 

Heavy metal and radionuclide concentrations in soils increase due to man-made pollution. One of the first entry points of such elements into plant ecosystems is the rhizosphere, defined as the soil under the biological, physical and chemical influence of roots. Arbuscular mycorrhizal (AM) fungi, symbiotic microorganisms associated with the roots of many plant species, provide a direct link between soil and roots and affect metal transfer to plants. The present chapter includes recent laboratory work and some research aspects stiU to be adressed on the contribution of AM fungi to plant metal uptake. The necessity to develop new and adapted approaches, such as compartment devices and root-organ cultures, to separate AM to root contribution to metal uptake is emphasized. Available data may be difficult to compare because they were obtained under different experimental conditions. However, they suggest that the transfer of heavy metals from AM fungi to plants may be metal specific. Further research should focus on the mechanisms involved in reduced or improved uptake of metals by mycorrhizal plants, on AM tolerance to metals and radionuclides and on AM functional diversity in polluted soils. AM contribution to metal uptake should also be quantified to include data in models of plant uptake. 

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