Kinetics of Ag-110m, Co-60, Cs-137 and Mn-54 bioaccumulation from water and depuration by the Crustacean Daphnia magna

Adam, C; Baudin, JP; Garnier-Laplace, J. Water, Air and Soil Pollution (2001) 125, 171-188.

As part of a research program on the transfer within freshwater ecosystems of the radionuclides present in the weakly radioactive liquid effluents from nuclear power stations, this article presents an assessment of the dynamics of zooplankton contamination from water. The experiments were carried out on young pre-adult daphnids, placed at a density of 250 individuals L-1, in 0.45 (mu)m filtered river water. In order to maintain the radionuclide contamination at a high level and to limit alterations in the chemical characteristics of the medium, the water was renewed daily. The dynamics of contamination were described by a one (Cs-137) or a two compartmental model ((110)mAg, Co-60 and Mn-54), taking into account the fluctuations of the radionuclide concentration in the water, as well as the growth rate of the daphnids. The contamination levels were described by the steady state value of the concentration factor, which was 2870 mL g(-1) wet weight, 320 mL g(-1) wet weight, 265 mL g(-1) wet weight and 30 mL g(-1) wet weight, for (110)mAg, Mn-54, Co-60 and Cs-137, respectively. During the depuration phase, radioactivity decrease in daphnids was a very fast phenomenon indicating that radionuclide adsorption to the surface was the major process involved in the contamination of daphnids. The two corresponding half-lives of the depuration kinetics were 10 min and 7 d, 20 min and 1 d and 3 hr and 1.5 d for Co-60, (110)mAg and Mn-54, respectively. The loss of Cs-137 was characterised by a single half-life of 0.3 d.