Availability of Cs-137 and Sr-90 for plants from various soil components

Accumulation of Cs-137 and Sr-90 by wild herbaceous plants is shown to depe nd on the contents of radionuclides in the labile fraction of soil humus. T he biological availability of radionuclides from various humus fractions ha s been estimated using pot experiments. It is shown that water-soluble inog anic forms Cs-137 and soluble cesium-fulvic associations are the fractions most available for the root uptake. Sr-90 is more available from the clay-h umus compounds. Peculiarities of the biological availability of cationic (e xchangeable) radionuclides and soluble radionuclide-organic compounds sugge st that exchangeable forms play the dominant role in the process of radionu clide uptake by roots.