Transfer pathways of Mn-54, Co-57, Sr-85, Ru-103 and Cs-134 in rice and radish plants directly contaminated at different growth stages

In order to study radionuclide transfer pathways related to direct contamin ation of plants, the above-ground parts of rice and radish plants were spra yed with a solution containing Mn-54 Co-57, (85)r, Ru-103 and (CS)-C-134 in a greenhouse at 5 or 6 different times. Showing little difference among ra dionuclides, the interception factor increased as plants grew to maturity. Its highest observed value was 0.94 in rice and 0.83 in radish. Weathering losses of the intercepted activity by harvest were 32-89% in rice and 32-85 % in radish depending on application time and radionuclide. Half lives for weathering loss were estimated to be longer on the whole for earlier applic ations. The translocation factor varied with application time by factors of 6-110 for hulled rice seeds and 2-23 for radish roots depending on the rad ionuclide. It varied with radionuclides by factors of 6-800 depending on ap plication time and plant species. It was highest in the plants sprayed duri ng active seed growth for rice and during early plant growth for radish. In general, Cs-134 and Co-57 had the highest translocation factors followed b y Mn-54, Sr-85 and Ru-103. Based on the experimental results, radionuclide concentrations in the edible parts of mature plants were predicted for unit deposition. (C) 2001 Elsevier Science Ltd. All rights reserved.