Analysis of radionuclides content in soil samples from area of Aleksandrovačka Župa, Serbia

Abstract

Naturally occurring radionuclide (uranium, actinium and thorium series and 40K) are widespread in the environment. In addition, significant amount of 137Cs may also be present in the soil as a result of accidents, such as Chernobyl accident. Thus, monitoring of radionuclides content in soil is of great importance. Aleksandrovac is small town in the western part of central Serbia and Župa is identified as the administrative territory of Aleksandrovac municipality. Nature of Aleksandrovačka Župa is under the long-lasting influence of anthropogenic factors, and therefore dominates altered natural landscape. Activity concentration of 226Ra, 232Th, 40K and 137Cs in 26 soil samples collected from different location in the territory of Aleksandrovačka Župa were determined and presented. All soil samples were milled and sealed in 0.5 l Marinelli beakers, and stored for six weeks in order to reach radioactive equilibrium between 226Ra and its descendants. All samples were measured by means of coaxial semiconductor HPGe detector (ORTEC GEM-30, 37% relative efficiency and 1.8 keV resolution for 60Co at 1332 keV line). The detector was calibrated using the standards in the same geometry spiked with common mixture of gamma-ray emitters certified by Czech Metrological Institute. The activity concentrations of radionuclides 40K and 137Cs in soil samples were determined directly by analyzing full-energy peaks of their principal energies at 1460.83 keV and 661.66 keV, respectively. The activity of 40K was corrected for the contribution of 228Ac (1459.14 keV). The activity of 226Ra was determined by analyzing full-energy peak at 186.21 keV, corrected for the contribution of 235U (185.72 keV) evaluated via 235U photo-peak at 143.77 keV and additionally approved by analyzing activity concentrations of its descendants (214Bi and 214Pb). Furthermore, the activity concentration of 232Th was determined by using the evaluated activity of its descendants (228Ac, 212Bi, 212Pb, and 208Tl). All obtained activity concentrations were corrected for the coincidence summing effect, applying the calculation method of Debertin and Schötzig (1990).