Transfer factors of natural radionuclides and Cs-137 from soil to plants used in traditional medicine in central Serbia

Abstract

Transfer factors of natural radionuclides and (CS)-C-137 from soil to plants used in traditional medicine were determined. The transfer factors (TF) were calculated as Bq kg(-1) of dry plant per Bq kg(-1) of dry soil. Mass activity concentrations of Ra-226, Th-232, K-40 and Cs-137 in soil and plant samples were measured with high purity germanium detector (HPGe). The concentrations of As, Co, Cr, Cu, Mn, Ni, Pb and Zn were determined, as well as the cation exchange capacity (CEC) and the content of exchangeable cations (Ca, Mg, K, Na). Wide ranges of values were obtained for all the metals, especially for Cr and Ni. The Absalom model was used for determination of the amount of Cs-137 transferred from soil to plant based on soil characteristics such as pH, exchangeable potassium, humus and clay contents. The estimated transfer factors were in the range from 0.011 to 0.307 with an arithmetic mean of 0.071, median of 0.050, geometric mean of 0.053 and geometric standard deviation (GSD) of 2.08. This value agreed well with that calculated from the measurements of 0.069, geometric mean 0.040 and GSD 3.19. Correlations between radionuclides, metals, physicochemical properties and transfer factors were determined by Spearman correlation coefficient. There was a strong positive correlation between Cs-137 transfer factor and the ratio of transfer factor for K and Cs-137. Principal Component Analysis (PCA) was performed in order to identify some pattern of data.