Chemical forms of gamma-emitting radionuclides in soils adjacent to the Chernobyl NPP.

Samples of sandy forest soils, meadow sandy-peat soil and meadow sandy-loam soil were taken at different sites within a 30-km zone around the Chernobyl NPP (ChNPP). The samples were extracted with water and a 0.1-N solution of ammonium acetate. The extracts were measured for gamma-radionuclides and stable cation content. The content of all mobile forms of the radionuclides present in the 0-10-cm soil layer accounts for 0.5-5% of the total radionuclide content in this layer, depending on the type of radionuclide and soil. Water soluble forms of the radionuclides were found in the 0-5-cm layer only. Exchangeable radionuclide forms were represented, as a rule, by radiocaesium in both the 0-5- and 5-10-cm layers. Content of Cs-137 exchangeable forms in the organic-mineral horizon were roughly inversely proportional to the sum of stable exchangeable cations and organic matter content. Forest vegetation takes up a significant share of the mobile forms of radiocaesium from the soils.