Studies of radionuclide concentrations in surface soil in and around fly ash disposal sites

The activity levels of some natural radionuclides and 137Cs in the surface soil layer (0–5 cm) within and outside three recultivated coal fly ash disposal sites have been determined by γ-ray spectrometry with an REGe detector. The activity of natural radionuclides from the 238U and 232Th 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 210Pb was observed. This can be explained as a result of the high 222Rn emanation from deposited fly ash covered with an insufficient layer of soil. The observed correlation between an excess of 210Pb and the concentration of anthropogenic radionuclide 137Cs in surface soil confirms the fact, that local geographic conditions can substantially influence the radionuclide depositional flux from the atmosphere to the soil.