The distribution of Pu-239+240 and Cs-137 isotopes in soils fractions in the Kaluga region

The article is dedicated to the study of the distribution of Pu-239+240 and Cs-137 in soil fractions in the Kaluga region. This study is relevant because it helps to fill in knowledge gaps about the distribution of radioactive isotopes in order to better understand their contribution to air pollution and predict their local redistribution due to wind-driven erosion. The main goal of the research was to analyze the patterns of Pu-239+240 and Cs-137 distribution in soil fractions within the “distant” Chernobyl fallout area using the example of Kaluga region, and to evaluate their impact on effective annual radiation doses resulting from inhalation. To accomplish this, various methods were employed, including “wet” sieving and the pipette technique for particle sedimentation. The content of Cs-137 was determined with the gamma-ray spectrometry method on a Canberra Industries spectrometer. The Pu-239+240 was estimated with the “Alpha-DUO” alpha spectrometry technique with prior radiochemical separation. For the study areas, there is a general trend towards an increase in radionuclide concentration in fine particles. The total radioactivity of Cs-137 in the background soil is estimated to be less than 12 Bq/kg and Pu-239+240 is 0.31 Bq/kg. For the uncontaminated area, there is a gradual increase in the plutonium concentration, it is consistent with the distribution of global fallout. For areas affected by the Chernobyl accident, the total 137Cs concentration ranges from 208 to 392 Bq/kg, significantly higher than the background levels. The gross content of Pu-239+240 in the soil ranges from 0.53 to 1.0 Bq/kg, which is similar to the level of global precipitation. A significant increase in radionuclide concentrations is observed in fractions lower than 38 microns for this area. The enrichment coefficients for plutonium vary from 0.16 to 27.4, and for Cs-137, they range from 0.9 to 13.2. Failure to consider the distribution of radionuclides in soil fractions may lead to an overestimation of internal radiation dose by more than 20 times due to inhalation intake.