RADIONUCLIDE DISTRIBUTIONS IN VERTICAL SOIL CROSS-SECTIONS OF THE CHERNOBYL NPP 30-KILOMETER ZONE ALONG THE WESTERN FALLOUT TRACK .3. SODDY-PODZOLIC SOIL, TURF

Radionuclide distributions in vertical cross sections taken in soddy-p odzolic soil and in turf along the western fallout track 5 km from the fourth block of the Chernobyl NPP are studied. The decrease of the co ntent of all radionuclides with depth in the soddy-podzolic soil in th e range 1-2 cm is constant with time (1987-1990) and is described to a first approximation by a semilogarithmic dependence of the specific a ctivity on depth. The vertical radionuclide distributions change with increasing depth depending on the nature of the radionuclide. The main portion of the radionuclides (greater-than-or-equal-to 90%) is concen trated in the range 0-2 cm. In turf, the decrease of the radionuclide contents in the cross-sectional layers with depth deviates from the se milogarithmic dependence. Each radionuclide exhibits a unique change w ith depth of its content in the cross-sectional layers. The radionucli des penetrate to greater depths than in cross sections taken in soddy- podzolic soil. Thus, only 40% of the radionuclides of their amount in the whole cross section is contained in the 0-2 cm layer in 1990.