Origin and behavior of radionuclides in sediment core: a case study of the sediments collected from man-made reservoirs located in the past mining region in Central Slovakia.

The analyzed sediments were taken from the man-made reservoirs (Velka Richnava, Rozgrund and Vindsachta) located in an area intensively mined for polymetallic ores since the end of the eleventh century (Banska Stiavnica region, Central Europe). The aims of this study were to determine the radioactivity of natural (Ra, Th, Pb) and artificial (Cs and Am) radionuclides, compare the radionuclides' distribution, and indicate the correlation of radioisotopes and their origin related to sediment properties. Two analytical techniques were used. Th, Ra, Am, and Cs were measured by means of gamma spectrometry and Pb was determined by its daughter radionuclide Po using alpha spectrometry. The results showed that the highest mean level of Ra (42.6 Bq·kg), Th (49.7 Bq·kg) and Pb (75.2 Bq·kg) was in the sediments collected from Rozgrund. The radioactivity of Cs and Am were present at a higher level in the layer related to Chernobyl (1986) accident and nuclear weapon test (1950/1960). The distribution of natural radionuclides was quite similar in all reservoirs. Chemometric analysis confirmed the radionuclides' origin and correlation between the analyzed parameters.