Distribution of natural radionuclides in alluvial gray humus (turf) typical soils around settlements of the Tyumen region

The aim of the work is to study the distribution of radiation parameters in the profile of alluvial gray humus (turf) typical soils of the floodplain of the Irtysh and Tobol rivers in the vicinity of settlements: flux density 222Rn, specific activity of natural radionuclides – 226Ra, 232Th, 40K, their effective specific activity. Measurements of the 222Rn flux density were performed by the KAMERA-01 radon monitoring system, and the specific activity of natural radionuclides using the SKS-99 Sputnik gamma-ray spectrometer. The ranges of specific activity of natural radionuclides in the soil profile of 226Ra are 3-26 Bq/kg; 232Th – 3-28 Bq/kg; 40K – 175-404 Bq/kg. The nature of the distribution of the specific activities of natural radionuclides 226Ra and 232Th in the soil profile of alluvial gray humus (turf) typical soils depends on their content in the soil-forming rocks and is not influenced by the physico-chemical properties of the soil – moisture, actual acidity and density of addition. The profile distribution of the specific activity of 40K revealed statistically significant correlations with the actual soil acidity. The average value of the effective specific activity of natural radionuclides (61 Bq/kg) in the soil does not exceed the safe level for the population living in the studied territories and environmental components – 100 Bq/kg. The pH from the soil surface is less than the level set in OSPORB-99/2010 – 80 mBq/(m2·s). Alluvial gray humus (turf) typical soils in the floodplain of the Irtysh and Tobol rivers in the vicinity of the settlements of Yarkovsky (Sorokino village), Vagaysky (Injura village, Vagai vil-lage) and Tobolsk (Russian Medyanki village, Ermakovo village, Ovsyannikovo village) districts of the Tyumen region represent a low risk exposure for humans. The results obtained are important as regional data in assessing the radiation safety status of the population living in the study area.