Studies on radionuclides in soils available for plants

One of the important factors in the studies of environmental impact originated from activities of nuclear installations is the geochemical behavior of the radionuclides. The determination of the transfer factor - TF, proposed by the International Union of the Radioecologists is one of the most used methodologies. The TF is specific for each soil, radionuclide and plant system, which make its determination a difficult task. It was used in this paper a methodology widely employed in studies of soil fertility, where the concentration of nutrients and available fraction to the plants are determined. The method consists in the extraction of the available species through the stirring of a soil, water and ion-exchange resin, a process that up to a certain extent simulates the action of the roots. The analyzed sample was obtained in the plateau of Pocos de Caldas, a region that is well know for its high natural activity. Radionuclides from the natural series were determined by using the alpha and gamma spectrometry and radiochemistry. The available fraction obtained for plants, 238 U, 234 U 232 Th, 230 Th, 228 Th, 226 Ra and 210 Pb were 2,72%, 2,37%, <0,7%, <1,1% <0,6%, 0,64%, 7,9% and 21,8%, respectively. (author)