Geochemical association of137Cs and239,240Pu in the oligotrophic and mesotrophic lake sediments

Geochemical association of¹³⁷Cs and^239,240Pu in the surface sediments from two oligotrophic and mesotrophic lakes in Japan was studied by sequential chemical extractions. The fractions separated were exchangeable and bound to carbonate, bound to oxides, bound to organic mattersulfides, and residual. The¹³⁷Cs and^239,240Pu were mainly associated with the organic matter-sulfides and residual fractions but exhibited the different vertical profiles at both lakes. The differences in association patterns between the lakes may be controlled by transport of these nuclides by organic settling particles to the bottom sediments and decomposition of the organics in the sediments.