Systematic survey of natural radioactivity of soil in Slovenia

Soil samples, from 70 points uniformly distributed over entire Slovenia, were analysed for 40K, 232Th and 226Ra using gamma spectrometry, and for 234U and 238U using alpha spectrometry. The following ranges and averages of activity concentrations (Bq kg−1) were obtained: 98–2600 and 800 ± 520 for 40K, 9–170 and 77 ± 33 for 232Th, 12–270 and 63 ± 44 for 226Ra, 12–84 and 34 ± 19 for 234U, and 11–90 and 34 ± 19 for 238U. With respect to lithology, the highest average values for 40K and 232Th were found at clastic sediments containing clay and for 226Ra on carbonate rocks. Based on the measured activity concentrations, terrestrial gamma dose rates were calculated. The total dose rate ranged from 15 to 260 nGy h−1, with arithmetic mean of 110 ± 49 nGy h−1, being the highest over carbonates.

► Systematic analysis of natural radionuclides on different lithological units.
► Chemical processes and interactions between radionuclides and soil.
► Spatial variation of natural radionuclides on different lithological units.
► Unique research of natural radionuclides in the karst environment.