MULTITRACER STUDY ON ABSORPTION OF RADIONUCLIDES IN ATMOSPHERE-PLANT MODEL SYSTEM

The absorption of atmospheric radionuclides by soybean plants was expe rimentally studied using a radioactive multitracer consisting of radio nuclides of Sc, Mn, Co, As, Se, Rb, Sr, Y, Eu, Gd, Yb, Hf, Re, and Ir. The soybean plants were cultivated in soil under no-rain conditions i n a box containing air in which multitracer-absorbed cellulose particl es were dispersed. The soil was covered with plastic film. After about one-month cultivation, the plants were harvested and washed with dilu te HCl solution. The leaves, stems, and beans were subjected to gamma- ray measurement. The radionuclides of As, Se, and Re were accumulated in the leaves, and those of Co, Se, and Rb were accumulated in the bea ns. Among them Se was accumulated to a large extent in the leaves and in the beans. Small amounts of the radionuclides of Co, Se, Rb and Re were found in the roots. Little absorption of these radionuclides into the soil occurred. These results indicate that various radionuclides in the atmosphere were absorbed through the soybean leaves and then tr ansported to the seeds. These findings must be taken into consideratio n for a complete understanding of the system of uptake of radionuclide s by the soybean plant.