Phytoextraction of thorium from soil and water media

Remediation of ecosystems that have been exposed to radionuclides is of great importance for many countries. At present the remediation efforts using existing technologies are rather expensive. Phytoremediation can serve as a perspective method for rehabilitation of the radioactive contaminated soils and wastes. Among other radio-nuclides, limited information is available on screening and selection of plants for thorium uptake. In our work short-term pot experiments in a greenhouse have been performed to study the phytoextraction of thorium by wheat seedlings grown in soil and different water media artificially contaminated with thorium. Addition of a small amount of thorium to the media resulted in a significant increase of thorium concentration both in roots and leaves of the wheat seedlings. The uptake of Th by roots depended of the media where the plants grew: it was more significant in water-grown plants. The rate of Th translocation from roots to leaves was approximately the same regardless of the growth medium. The bioaccumulation of Th in the wheat resulted in the removal of Th from the soil and water. During the short-term vegetation test concentration of Th in all the media decreased: in water - 2 - 5 times, in soil - 1.7 times. Th accumulation in the wheat seedlings affected concentrations and relationships between other elements in the plants. More significant changes were found in the wheat grown in doubly distilled water and in nutrient solution. The most affected part of the plants was the root system.