Abstract
A small simulated ecosystem was used to get informations on accumulation of radionuclides by freshwater organisms. The simulated ecosystem was made up of an aquatic plant(Vallisneria sp.), a shrimp(Paratya compressa), clams(Unio douglasiae, Anodonta woodiana and Corbicula japonica), a snail(Cipangopaludina japonica) and fishes(Carassius auratus and Cyprinus carpio) in a glass aquaria containing freshwater and sediment. During the experiment, the aquaria was maintained with illumination for half a day, slow circulation of water and control of water temperature at 20 degrees centigrade and without aeration, filtration of water and feeding to the organisms. Radionuclides used in the experiment were 54Mn, 57Co, 85Sr, 103Ru, 125I, 137Cs and 141Ce. In several days after addition of the radionuclides into the aquaria, most part of the radionuclides was accumulated by sediment. Consequently activity level of the radionuclides in water became low. In spite of low radioactivity level in water, organisms showed relatively high accumulation of the nuclides. This suggested the participation of the radioactive sediment on accumulation of radionuclides by organisms in a freshwater ecosystem.
