Distribution of natural radionuclides in anthrosol-type soil

Abstract

Taking into account the importance of distribution and transfer of radionuclides in the soil-water-plant system, especially in agricultural fields, in this study, natural radionuclide determination in regosol-type soil was performed. The correlations between main soil properties and the contents of natural isotopes ^{238}U, ^{226}Ra, ^{232}Th, and ^{40}K in agricultural soil and their distribution through the soil depth was studied. For determination of natural radionuclide activity concentration, we used the CANBERRA HPGe detector, applying the gamma spectrometry method. The investigation was performed on an experimental peach tree field characterized by a anthrosol type of soil, derived from the chernozem type of natural soil. The effect of measured soil properties on activity concentration levels was analyzed by simple and multiple linear regression analysis. Considering the linear model, in our soil profiles of 0-80 cm depth, clay content was positively related with ^{238}U, ^{226}Ra, and ^{40}K, and about 30% of the variation of those radionuclides was explained. Sand fraction was negatively related with ^{238}U, ^{226}Ra, ^{232}Th, and ^{40}K and the correlation was medium, except for ^{226}Ra (r = -0.68). The joint effect of pH, carbonates, humus, clay, and sand contents on natural radionuclide distribution in the 0-80 cm layer was found by multiple linear regression analysis. Radionuclide behavior was explained by the R-squared statistic. The investigations of uranium distribution showed that when the soil layers of 0-20 cm and 60-80 cm are considered together, uranium behavior is affected by soil pH and the content of humus, carbonates, and clay. Multiple regression analysis of ^{226}Ra, ^{232}Th, and ^{40}K activities in soil layers of 0-20 cm and 60-80 cm showed that their lower mobility and uniform depth distribution are associated with small variations of carbonates along soil depth and mineral composition of the parent materials, while the soil pH had no effect on their behavior.