Distribution of natural radionuclides in the forest soils

The paper presents results of investigation of regulatory of the specific activity of 40K, 226Ra and 232Th distribution in the sod-podzolic soil in forest plantations growing in various types of forest growing conditions. The absorbed dose rate of external gamma radiation at a height of 1 m, was estimated as well. Methods for constructing normal probability graphs and histograms, as well as the statistical calculation of criteria for verification of the distribution normality (asymmetry of the set of b1 , curvature of the set of b2 , Shapiro-Wilk, Epps-Palli, Frozini, Kolmogorov-Smirnov) were applied. It was found that the content of natural radionuclides in the sod-podzolic soil in forest plantations may be described by a lognormal law, while the range of specific activity of 40K is from 200 to 500 Bq/kg, 232Th is 10-20 Bq/kg, 226Ra is 10-30 Bq/kg, the estimated absorbed dose rate is 20-50 nGy/h. It was found that the use of the smaller soil classification units, the granulometric composition of the soil and the underlying rock as well as the distribution of 40K, 226Ra and 232Th content in the soil of the edaphotopes A2 and B2 and estimated absorbed dose rate, could be described by the normal distribution law. The results obtained expand and complement the knowledge on natural radionuclides distribution in the environment, and can also become the basis for assessment of the natural level of biota irradiation in various soil and environmental conditions.