Potential of Energy Willow Plantations for Biological Reclamation of Soils Polluted by 137Cs and Heavy Metals, and for Control of Nutrients Leaking into Water Systems

Willow is a low-maintenance crop that has potential for energy production and enhancing the local environment. The area of commercial plantations of willow in Europe is mostly concentrated in Sweden, with more than 20 000 ha. Willow trees are used not only for energy production, but also for reclamation of polluted soils because a plantation may grow for 20-25 years, with a three-year period of harvesting. Our research covers issues of reclamation of soils contaminated by radionuclides and heavy metals, and decreasing of eutrophication of water ecosystems with using willow plantations. The field studies of phytoremediation of soil contaminated by Cs-137 by willow plants were conducted in eastern Belarus, in the area where agricultural activity was banned after Chernobyl disaster. This region is heavily polluted with Cs-137 (from 185 to 555 kBq/m(2)) and heavy metals. The transferring factors of accumulated Cs-137 and heavy metals from the soil to willow biomass were determined. The field experiments showed that willow does not accumulate actively Cd and Pb, but it accumulates Zn, Cu and Mn intensively. The potassium application decreases the accumulation of Cs-137 in willow biomass and increases accumulation of Cu, Zn and Mn, but has no influence on accumulation of Cd and Pb. Our results confirmed that soils polluted with radionuclide and heavy metals could be used for willow cultivation as energy crop, if adequate management is applied. The different potential of the willow species concerning heavy metals accumulation was also established. The yield of willow biomass on polluted soils achieved 11.5-12.8 DMg ha(-1)per year, depending on variety, that is competitive with the ordinary yield of willow on mineral fertile soils. Willow plantations also may be used for accumulations of nutrients like nitrogen and phosphorus in watersheds. It enables to decrease impact for water ecosystems and to control eutrophication.