Radioactivity and Radon potential of the terra rossa soil

In the Slovenian and Croatian karstic region, four locations of terra rossa soil were selected, in which soil samples were analysed by gamma spectrometry, and radon activity concentration (sum of 222Rn and 220Rn) were measured in soil gas at points within a regular 24m×24m grid. Levels (Bqkg-1) of naturally occurring radionuclides obtained in the upper 15 cm layer of soil were: 320–510 for 40K, 50–85 for 228Ra, 52–75 for 226Ra and 52–70 for 238U. Measurement sites were found to lie beyond the impact of the nearby coal-fired power plant. Man-made 137Cs was found at levels from 10 to 25Bqkg-1 in the sea shore region, and 105–250Bqkg-1 at inland locations. Although the uranium/radium contents in the terra rossa   soil at different points were equal within experimental error, radon activity levels in soil gas differed substantially from point to point, and could range from 25 to 420kBqm-3 in a dry and from 0.1 to 2.7kBqm-3 in wet soil.