The classification of Ukrainian soil systems on the basis of transfer factors of radionuclides from soils to reference plants

Transfer factors (TFs) for 137 Cs and 90Sr from soil to plants were measured for oats potatoes and beetroot at three sites contaminated by the Chernobyl accident over four years (1999-2002). In addition, data collected from many sites since 1987 were considered. The TF values were independent of the level of radionuclide contamination in the soil but declined with time after contamination. The decline followed a two-component model for 137Cs and a one-component model for 90Sr. Ratios of TFs between different crops varied from year to year but averaged over several years such reference ratios could be used to give an acceptable comparison of crops in different regions. A semi-empirical method was developed in which normalised values of soil pH, organic matter and adsorption capacity are used to characterise soils so that TF values may be compared. It is proposed that this could be the basis for a radioecological soil classification. (author)