Distribution of 226Ra, 232Th, and 40K in Dark Gray Forest Soils with Different Carbonate Horizon Depth

The 226Ra, 232Th, and 40K vertical profiles were studied in relation to the following soil properties: pHH2O, the sum of exchangeable Ca2+ and Mg2+, the saturation with bases, and the content of humus and mobile forms of phosphorus and potassium. An increase in the specific activity of 226Ra, 232Th, and 40K as a result of humus accumulation and the biogenic accumulation of mobile forms of potassium and phosphorus was detected in the 0- to 10-cm layer of the A horizon in the soil under an oak forest. The removal of 226Ra from the middle part of the profile of dark gray forest deep-carbonate soil was recorded. A positive correlation between the specific activity of 226Ra and the total exchangeable bases of Ca2+ and Mg2+ in the A, A(AE), AB, and deeper (B1, B2, and B3) horizons was revealed. This indicates the interrelated behavior of these elements-analogues. The removal of 232Th from the A(AE) horizon and its accumulation in the AB horizon under conditions of local podzolization of dark gray forest soil in a birch forest was observed.