Transfer of natural radionuclides from hay and silage to cow’s milk in the vicinity of a former uranium mine

After the closure of the former Žirovski Vrh uranium mine in Slovenia, mining and milling wastes were deposited on two waste piles, which are located close to the mine. These wastes contain elevated levels of natural radionuclides from the uranium decay chain. Due to different migration processes (erosion, aerial deposition, through groundwater), these radionuclides can be transported via fodder into cow’s milk, which is an important foodstuff for Slovenian people. Therefore, natural radionuclides were analysed in the transfer food chain from soil to cow’s fodder and cow’s milk. After sampling, 238U, 234U, 230Th, 226Ra, 210Pb and 210Po were determined using radiochemical separation methods and alpha spectrometry or proportional counting. Hay and silage to milk concentration ratios (kg dry weight L−1) were calculated and were 0.260 for 238U, 0.255 for 230Th, 0.070 for 226Ra, 0.021 for 210Pb and 0.019 for 210Po. The calculated annual ingestion dose due to milk consumption for the natural radionuclides analysed was 9 μSv/year for adults and 389 μSv/year for infants with the highest contribution of 210Po (51% for adults and 63% for infants) and 210Pb (36% for adults and 24% for infants). This study provides new data quantifying the transfer of natural radionuclides to milk, which is a parameter for which there have been very few previously reported values.

► Transfer of natural radionuclides from soil via cow’s feed to milk was studied.
► The highest soil to silage and hay transfer factors was found for 210Pb.
► The highest silage and hay to milk concentration ratios was found for 238U.
► The annual ingestion dose due to milk consumption was 389 μSv/year for infants.