Distribution of Natural Radionuclides and 137Cs in Urban Soil Samples from the City of Novi Sad, Serbia-Radiological Risk Assessment

This work presents the natural radioactivity distribution of 21 surface soil samples taken in the city of Novi Sad, Serbia. The analysis for radioactivity was performed using a gas low-level proportional counter for gross alpha and gross beta activity, while the specific activities of radionuclides were determined using HPGe detectors. The gross alpha activity of 20 samples was below the minimum detectable concentration (MDC), while in 1 sample it was 243 Bq kg(-1); the gross beta activity ranged from the MDC (11 samples) to 566 Bq kg(-1). The gamma spectrometry measurements showed naturally occurring radionuclides Ra-226, Th-232, K-40, and U-238 in all investigated samples, with average values (Bq kg(-1)) of 33.9, 36.7, 513.8, and 34.7, respectively. Natural radionuclide U-235 was detected in 18 samples with activity concentrations in the range of 1.3-4.1 Bq kg(-1), while in the other 3 samples, the values were below the MDC. The artificial Cs-137 radionuclide was detected in 90 percent of the samples, with a maximum value of 21 Bq kg(-1), while the other artificial radionuclides were not detected. Based on the obtained concentrations of natural radionuclides, hazard indexes were estimated, and radiological health risk was assessed. The results present the absorbed gamma dose rate in the air, annual effective dose, radium equivalent activity, external hazard index, and lifetime cancer risk.