STUDIES OF RADIONUCLIDE CONCENTRATIONS IN SURFACE SOIL IN AND AROUND FLY-ASH DISPOSAL SITES

The activity levels of some natural radionuclides and Cs-137 in the su rface soil layer (0-5 cm) within and outside three recultivated coal f ly ash disposal sites have been determined by gamma-ray spectrometry w ith an REGe detector. The activity of natural radionuclides from the U -238 and Th-232 series in the soil samples ranged from 7.5 to 77 Bq/kg . No significant differences in the activity of concentrations within and outside of two of the disposal sites have been found. However, in the vicinity of one site an abnormally high depositional flux of Pb-21 0 was observed. This can be explained as a result of the high Rn-222 e manation from deposited fly ash covered with an insufficient layer of soil. The observed correlation between an excess of Pb-210 and the con centration of anthropogenic radionuclide Cs-137 in surface soil confir ms the fact, that local geographic conditions can substantially influe nce the radionuclide depositional flux from the atmosphere to the soil . (C) 1998 Elsevier Science B.V. All rights reserved.