Assessment of the Contamination Level of a Podzolized Chernozem with Nuclides in a Long-term Land Use

Prolonged systematic application of mineral fertilisers contributes to increasing the yielding capacity of agricultural crops. However, it can lead to significant changes in the composition, properties and formation of agricultural soil regimes. The findings of the research have shown that the application of mineral fertilisers leads to the change of radioactive nuclides content in the soil. The research was conducted under conditions of a long-term stationary field experiment (Uman, Ukraine), using different rates of mineral fertilisers N₄₅P₄₅K₄₅, N₉₀P₉₀K₉₀ and N₁₃₅P₁₃₅K₁₃₅. Soil samples (podzolized chernozem) were selected from the depths of 0 – 20, 20 – 40 and 40 – 60 cm. Specific activity of radionuclides was determined by the spectrometric analysis. Using experimental results we have demonstrated that under a long-term application (50 years) different rates of mineral fertilisers effect the specific activity of radioactive isotopes in the soil (²²⁶Ra, ²³²Th, ⁴⁰K, ¹³⁷Cs, ⁹⁰Sr). The specific activity of radionuclides in a podzolized chernozem and in winter wheat grain was established. Winter wheat plants accumulated ²³²Th at the highest levels, but the use of fertilisers reduced it in a larger mass of the crop. The absorption of radioactive nuclides by winter wheat grain grown after peas and silage corn depending on fertilisation changed similar to growing it after clover as a previous crop. According to the data of specific activity of radioactive nuclides in the soil and winter wheat grain, the coefficient of their biological absorption was calculated.