Analysis of specific radionuclides activity variations in soil within geotectonic units of Republic of North Macedonia

To establish baseline values for concentrations of terrestrial radionuclides for the Republic of North Macedonia, a survey covering the entire territory was performed. The 213 soil samples were collected from regions around the major settlements and cities, approximately evenly distributed over the geotectonic units which constitute the country's geological foundation. The specific activities of radionuclides were measured by gamma spectrometry. The following geometric mean values and geometric standard deviations were obtained: 550 Bqkg–1 (1.47) for 40K, 37 Bqkg–1 (1.53) for 226Ra, 38 Bqkg–1 for 238U, and 38 Bqkg–1 (1.53) for 232Th in dry soil. The relation between specific activities of natural radionuclides and geology was investigated. Correlation between radionuclides, which may serve as additional geochemical indicators, and geology could not be found convincingly. Mutual correlations between 226Ra, 238U, and 232Th activities were found to be high (Spearman ρ about 0.8), whereas the ones between these and 40K are a bit lower, somewhat above ρ= 0.6.