Uptake of 137Cs by fungi and plants due to potassiumfertilization in Heby municipality in response to theChernobyl nuclear accident
Radiocaesium137CsPotassiumPotassium fertilizationForest plantsFungi;CountermeasureChernobyl nuclear accident
The fallout from the Chernobyl nuclear accident resulted in large deposits of caesium, iodineand strontium as well as noble gases in various parts of Sweden. 137Cs has a radioactive halflifeof about 30 years and is therefore one of few radio-fission products remaining inmeasurable quantities in the Swedish soil. Radiocaesium behaves similarly to potassium insoil-plant systems and is easily absorbed by plants. It is important to understand how 137Csbehaves in different ecosystems in order to minimize the risk toward humans.The aim of this study was to determine how potassium fertilization influences radiocaesiumcontent in different forest plants and fungi. Potassium fertilizer was spread once in 1992 withapproximately 200 kg KCl per ha. The method of determining the 137Cs activity concentrationinvolved collecting forest plants and fungi samples from the sites used in previous studies.These samples were then placed in a High-Purity Germanium Coaxial Photon Detector toaccurately determine the 137Cs activity concentration levels. The results from this study werecompared with results from earlier studies made on the same sites between the years of 1992and 2005. This comparison was carried out in order to observe and estimate any long-termtrends.The results show that there is a large variation in the 137Cs activity concentration levels for theeight different fungi species found and analysed. Cortinarius semisanguineus, Cortinariuscinnamomeus and Rozites caperata were found to be the fungi species with the highest 137Csactivity concentration levels. Taking the previous years into account, the majority of the fungispecies show a decrease in 137Cs activity concentration for the potassium fertilized area,which would mean that it is possible to use potassium fertilization in order to reduce the 137Csactivity concentration uptake in fungi.With regard to plant species, it was determined that heather is the plant that shows the highest137Cs activity concentration levels. When comparing the levels of 137Cs in the plant specieswith those found in previous studies it clearly shows that the use of potassium fertilization asa countermeasure reduces the 137Cs activity concentration uptake in all plant speciesmeasured.