Geochemical association of Cs-137 and Pu-239,Pu-240 in the oligotrophic and mesotrophic lake sediments

Geochemical association of Cs-137 and Pu-239,Pu-240 in the surface sediment s from two oligotrophic and mesotrophic lakes in Japan was studied by seque ntial chemical extractions. The fractions separated were exchangeable and b ound to carbonate, bound to oxides, bound to organic matter-sulfides, and r esidual. The Cs-137 and Pu-239,Pu-240 were mainly associated with the organ ic matter-sulfides and residual fractions but exhibited the different verti cal profiles at both lakes. The differences in association patterns between the lakes may be controlled by transport of these nuclides by organic sett ling particles to the bottom sediments and decomposition of the organics in the sediments.