Radioactivity levels and heavy metals in the urban soil of Central Serbia

Radioactivity concentrations and heavy metal content were measured in soil samples collected from the area of Kragujevac, one of the largest cities in Serbia. The specific activities of Ra-226, Th-232, K-40 and Cs-137 in 30 samples were measured by gamma spectrometry using an HPGe semiconductor detector. The average values +/- standard deviations were 33.5 +/- 8.2, 50.3 +/- 10.6, 425.8 +/- 75.7 and 40.2 +/- 26.3 Bq kg(-1), respectively. The activity concentrations of Ra-226, Th-232 and Cs-137 have shown normal distribution. The annual effective doses, radium equivalent activities, external hazard indexes and excess lifetime cancer risk were also estimated. A RAD7 device was used for measuring radon exhalation rates from several samples with highest content of Ra-226. The concentrations of As, Co, Cr, Cu, Mn, Ni, Pb and Zn were measured, as well as their EDTA extractable concentrations. Wide ranges of values were obtained, especially for Cr, Mn, Ni, Pb and Zn. The absence of normal distribution indicates anthropogenic origin of Cr, Ni, Pb and Zn. Correlations between radionuclide activities, heavy metal contents and physicochemical properties of analysed soil were determined by Spearman correlation coefficient. Strong positive correlation between Ra-226 and Th-232 was found