Radionuclides in raised bogs: a case study of Bór za Lasem

Bór za Lasem is a raised bog in the Orawsko-Nowotarska Valley (southern Poland). About half of the Bór za Lasem area has been exploited while the rest is undisturbed. Peat samples from both parts of the bog were analysed. Measurements of 137Cs, 134Cs, 239,240Pu, 238Pu, 40K, 228Ra, and 226Ra activity concentrations in all samples were performed. Comparison of the results of radiocaesium and plutonium activity concentrations reveals the highest activity concentrations of radionuclides in the undisturbed part of the peat-bog area. The radiocaesium content decreased with depth, whereas the plutonium concentration had a maximum value at a depth of 15-20 cm. The lowest activity concentrations were found in the exploited part of the bog. Potassium and radium isotopes were detected only in shallow openings within the heavily exploited part of the bog, which might suggest partial mixing of the peat with the mineral sub-soil. The growth rate of the top layer of the undisturbed part of the bog obtained from plutonium distribution was estimated as approximately 0.5 cm per year.