Plutonium and americium behaviour in soil-vegetation cover of natural and semi-natural ecosystems

The results of investigations of transuranic elements { H , , M 0 P u and 2 4 'Am) behaviour in the soil-vegetation cover of natural and semi-natural ecosystems in the regions of Belarus contaminated as a result of Chernobyl acci­ dent have been summarised. The parameters of plutonium and americium vertical migration have been estimated for typical soil varieties; the radionuclides accumulation coefficients have been defined for dominating species of meadow and forest vegetation. The dynamics of change in physico-chemical state of plutonium and americium (the share and geochemical stability of "hot" particles, the ratio between fixed and mobile forms) has been analysed in various types of soils in the post-chernobyl period. It was established that the content of exchangeable 2 3 2 4 Pu and M I A m does not exceed 12.5%, the largest part of radionuclides is in fixed form in composition of soil humus and organo-mineral components. The linear rate of vertical migration of plutonium and americium in soils is 0.14-1.25 cm/year. Simultaneous interaction of different agrochemical parameters and natural conditions masks the influence of individual soil properties on migration rate, but the correlation with humidity has been reviled. The ac­ cumulation coefficients of americium in the system "soil-plant" are 1 . 2 4 times higher that those for plutonium. The method of reduction in the bioavailability of transuranic elements has also been proposed.