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

Resumo

The ²²⁶Ra, ²³²Th, and ⁴⁰K vertical profiles were studied in relation to the following soil properties: pH_H2O, 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.