A campaign of discrete radon concentration measurements in soil of Niška Banja town, Serbia

The first radon soil gas survey in Serbia, using passive detectors (SSNTD, CR-39), was carried out in June 2005 at field sites in Niska Banja town. The aim of the survey was to identify risk zones characterised by high levels of this radioactive gas. Radon measurements were made at the depth of 50 cm, in the ground according to a systematic grid pattern. Furthermore, at all 48 measurement points, the surface gamma dose rates in the air was also measured at the same locations and soil samples were collected for gamma spectrometric analysis for the radionuclides 226Ra, 228Th and 40K. Radon concentrations were found to range from 1270 to 155 000 Bq m - 3 with an average of 33 765 Bq m - 3 and a median value of 12 626 Bq m - 3 . The geometrical mean value and geometrical standard deviation were calculated as 16 160 Bq m - 3 and 3.5 Bq m - 3 , respectively. Gamma dose rate varies from 92 to 316 nGy h - 1 , with an average of 132 nGy h - 1 . The radium content in collected soil samples ranges from 24 to 1810 Bq kg - 1 with an average of 187 Bq kg - 1 . High correlations ( r 2 > 0.8 ) between soil gas radon concentration, gamma dose rate and 226Ra content in soil were found for each pair. The distribution of radon concentrations in soil gas shows bimodal shape.