Physico-chemical behavior of radionuclides in seawater

To elucidate the physico-chemical state of radionuclides in seawater in relation to uptake by the marine biosphere, the physico-chemical behavior of radiocobalt, radioruthenium and radiocerium in seawater was investigated by electrodialysis, high-voltage paper electrophoresis together with paper chromatography for nitrosylruthenium complexes. Most of the radiocobalt in a seawater medium behaved as dialytic cations. However, these cationic species were not necessarily simple divalent ones, because their electrophoretic bands were rather diffuse and showed two peaks temporarily. The electroneutral form also increased with aging. Furthermore from the results of adsorption behavior to chelating resin, the formation of organic complexes of cobalt was suggested in a seawater medium containing dissolved organic matter such as glycine or chlorella culture filtrate. The radioruthenium in seawater showed relatively a number of well-defined species which could be readily classified into anionic, cationic, electroneutral, colloidal or particulate, non-dialytic and more or less absorbable species. The radioruthenium in the chloro and nitratonitrosylruthenium complexes occurred mainly electroneutral and anionic species, while nitro- and binuclear oxygen-bridged nitratonitrosylruthenium complexes showed dominant anionic species. The hydrolysis of higher nitro- and nitratonitrosylruthenium complexes to lower ones was demonstrated in a seawater medium with aging by paper chromatography. The radiocerium in seawater showed initially cationic species. However, the electroneutral and anionic species were demonstrated by electrodialysis with aging. The radiocerium were strongly adsorbed on filter paper at the starting band in paper electrophresis, presumably because of the formation of strongly adsorbable or isoluble hydrolytic species or particle formation. (auth.)