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

Abstract

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 K-40, (37) Bqkg(-1) (1.33) for Ra-226, 38 Bqkg(-1) for U-238, and 38 Bqkg(-1) (1.53) for Th-232 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 Ra-226, U-238, and Th-232 activities were found to be high (Spearman rho about 0.8), whereas the ones between these and K-40 are a bit lower, somewhat above rho = 0.6.