Resultat av tjugofem års mätningar av Cs-137-halter i älg i Uppsala län

Abstract: At the end of April 1986 reactor number 4 of the nuclear power plant at Chernobyl explod-ed and large amounts of radioactive particles were then released into the atmosphere due to both the explosion as well as the consecutive fire of the graphite core. A cloud of radioac-tivity was spread over the northern hemisphere, including Sweden, due to the prevailing wind directions. The radioactive particles were washed out from the cloud by rain and snowfall in some areas of Sweden and deposited on the ground. The deposited radionu-clides, primarily cesium and iodine isotopes, were later absorbed into the soil and taken up by the roots of the plants. Some of these radionuclides, like 137Cs, still persist in some of the terrestrial ecosystems at relatively high concentrations which lead to contamination of the meat of moose, roe deer and wild boar even today.The two municipalities Heby and Uppsala, in the eastern part of central Sweden, experi-enced a relatively large deposition of 137Cs which resulted in high levels of 137Cs in moose and other game. I have undertaken a study to measure levels of 137Cs in moose from Heby and Uppsala during the hunting season in 2010. Data for each moose regarding parish and date were also recorded together with age, sex and carcass weight respectively. I have also analyzed a database containing similar data as above for approximately 3 500 moose hunt-ed between 1986 and 2009.The results support previous findings pointing to large variations of 137Cs activity con-centrations in moose both within but also between years. The data reveal that the average level of 137Cs is higher in young moose than in the adult moose. The results further show that the effective half-life of 137Cs in moose is long and close to its physical half-life of 30 years. The 62 samples collected in this study were assembled during the hunting season of 2010. All samples but one showed 137Cs levels well below the allowed current limit of 1 500 Bq/kg (f.w.) in game meat for sale. The average value was found to be 340 Bq/kg (f.w.). The highest concentration was found in a male calf from Huddunge showing 1 730 Bq/kg (f.w.).