Absorption behavior of technetium and rhenium through plant roots

Office of Biospheric Assessment for Waste Disposal, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555, Japan

Abstract

The absorption behavior of technetium (Tc) and rhenium (Re) through plant roots was studied using nutrient solution culture. Radish samples, grown in culture solutions for 20-30 days in a greenhouse, were transferred into plastic vessels containing nutrient solutions contaminated with multitracer solutions including ^95mTc and ¹⁸³Re. The plant samples were grown individually for 1-7 days under laboratory conditions. The activities of radionuclides in nutrient solutions and oven-dried plant parts (roots, fleshy roots and leaves) were measured with Ge detecting systems. The concentrations of ^95mTc and ¹⁸³Re in the nutrient solutions after harvesting the plants were almost the same as those in the initial solution, though about 2 mL of the nutrient solution was lost per day per plant pot due to transpiration. Possibly, the radionuclides were taken up with water through the plant roots. The distributions of Tc and Re in the plants showed no differences, thus, soluble Tc and Re absorption mechanisms by plant samples were the same. It is suggested that Re could be used as a geochemical tracer for Tc in soil environments.