Radiocaesium retention in bog meadows: an analysis based on soil properties

The vertical distribution of ¹³⁷Cs in peat bog soils in the remote period after the Chernobyl Nuclear Power Plant accident (ChNPP, 1986) was investigated. The study was conducted on bog meadows in the Bryansk region of Russia. Soil samples were taken at 4 locations: 2 sites on lowland bogs and 2 sites on transitional bogs. Fifteen years after the accident, analysis of soils showed that the peak of ¹³⁷Cs activity was still in the upper 10-cm layer. The highest percentage of the initial ¹³⁷Cs deposition (92%) has been observed in the top 10-cm layer in the drained transitional bog. The lowest part of the initial ¹³⁷Cs deposition (40%) has been found in 0-10-cm horizon in lowland bog with the deep peat layer. The findings revealed that elevated soil moisture promotes ¹³⁷Cs downward migration. It was shown that ammonium has a major impact on mobility of ¹³⁷Cs in bog soils. On average, the soil solution NH₄⁺ concentrations exceeded the K⁺ concentrations by about a factor 5. A significant linear relationship was found between the rates of ¹³⁷Cs removal from the top layers with the soil solution NH₄⁺ concentrations.