60Co retention by a freshwater planktonic alga Scenedesmus obliquus

This paper presents the results of various decontamination experiments aimed at evaluating (60)Co retention by Scenedesmus obliquus, and the respective roles played by absorption and adsorption in the contamination of the alga by this radionuclide. The physiological condition of cells is not involved in radiocobalt desorption, which seems to indicate that the phenomenon is of a passive nature. When the precontamination time is extended, the proportion of adsorbed (60)Co decreases, and the final percentage of radionuclide retained increases. These results are confirmed by bringing cells into contact with a strong chelating agent. The elimination of (60)Co in the presence of EDTA undergoes a sharp decrease which is correlated with the increase in the duration of the precontamination phase. The use of a weaker complexing agent, such as NaCl, leads to the hypothesis of there being 2 types of (60)Co receptor on cell membranes.