Investigation into 137Cs found in the soil profile within Vilnius region and estimation of inhabitants exposed to 137Cs transfered through the food chain

Abstract

The article describes the results of the radiological measurements of 137Cs in the soil profile, explains vertical migration coefficients of this radionuclide and discusses internal doses of 137Cs found in food and received through the food chain from soil to milk and meat. Sampling was performed in the northern part of Vilnius district and covered the territories, including Antakalniai village, territory in the south east close to Maišiagala, Mykoliškių village, Karveliškės rural region, territory in the east from Nemenčinė village and Stražninkai rural region. Radiological investigation into soil at a depth of up to 30 cm showed that the concentration of 137Cs activity was in the range from 0.6±0.4 Bq/kg to 5.3±0.4 Bq/kg. The vertical migration of 137Cs indicated two pikes in five sampling places. The first one is related to the contamination of the environment after the accident at Chernobyl NPP, whereas the second one – to the contamination of territory during the tests on nuclear weapons in open air in northern hemisphere. These pikes were not detected in the soil samples taken close to Antakalniai village. Thus, a conclusion that soil was disturbed during agricultural works at the sampling place was made. The highest concentration of 137Cs activity is located at a depth of 5–10 and 15–20 cm where radiocesium is available for vegetation and can get through the food chain to humans. Public estimation shows that the highest dose of 137Cs found in milk and meat has been discovered in Stražninkai (5.5±0.1 μSv) while the lowest one – in a small village near Maišiagala (2.3±0.1 μSv). These doses constitute only 0.5% of annual dose limit for public.

Vidutiniškai didžiausi gretimų dirvožemio sluoksnių savitųjų aktyvumų santykio koeficientai gauti iš 1 (0–5 cm) į 2 (5–10 cm) bei iš 3 (10–15 cm) į 4 (15–20 cm) sluoksnius. Taigi didžiausioji dirvožemio tarša 137Cs tebėra dar pakankamai negiliai, t. y. 5–10 bei 15–20 cm gylyje, lengvai prieinama augalų šaknims, tad per maistą gali patekti žmogui. Įvertinta, kad didžiausią metinę efektinę dozę, 137Cs patekus į pieną bei galvijų mėsą, gauna Stražninkų kaimo gyventojai (5,5±0,1 μSv), mažiausią – gyventojai, įsikūrę netoli Maišiagalos (2,3±0,1 μSv). Ši apšvita nėra reikšminga radiacinės saugos požiūriu, nes net didžiausios 137Cs savitojo aktyvumo dirvožemyje ir žolėje vertės gali lemti apie 0,5 % Lietuvos higienos normų leistinos gyventojui metinės apšvitos.