| Popis: |
The Novohradské Mountains were increasingly contaminated with cesium-137 in places where large amounts of radiocesium were washed out of the radioactive cloud caused by the accident of the Chernobyl nuclear power plant on April 26, 1986. Another source of cesium-137 was the testing of nuclear weapons, which was in the 50s and 60s of the 20th century carried out in the atmosphere of nuclear powers. From contaminated soil, cesium-137 enters the food chain and thus causes internal contamination of the population. For this reason, the activity concentration of cesium-137 in food (especially in edible mushrooms) is regularly determined. The aim of this thesis was to compare the activity concentrations of cesium-137 in samples of edible fungi collected in selected localities of the Novohradské Mountains. Transfer factors in individual fungal species were determined and compared. The thesis also focused on the comparison of the activity concentration of cesium-137 in the cap and in the stem of the mushroom. The samples were measured by gamma spectrometry. The values of activity concentration of cesium-137 in edible mushrooms differed according to their classification into the systematic group. Higher values of activity concentrations were measured in basidiomycete fungi compared to lower values recorded in gill fungi. High values of activity concentrations of cesium-137 have been repeatedly found, especially in the imleria badia (Xerocomus badius). The lowest value of the activity concentration of cesium-137 was measured in the representative of the parasol mushroom (Macrolepiota procera). The transfer factor as a ratio between the activity concentration of cesium-137 in the mushroom and the activity of cesium-137 in the soil is an important parameter for estimating the dose of internal exposure to radionuclides that a person receives in contaminated foods. The highest determined transfer factors were calculated for imleria badia (Xerocomus badius), the blusher (Amanita rubescens) and golden chanterelle mushroom (Cantharellus cibarius). Out of a total of 58 samples, in 78 % of the samples the values of the activity concentration of cesium-137 in the cap were higher than the values of the activity concentration in the stem and in 22 % of the samples the activity concentrations in the cap were lower than in its stem. The determined cap/stem ratio confirmed that three quarters of the edible mushrooms examined preferentially accumulated cesium-137 in the cap and one quarter of the mushrooms more accumulated cesium-137 more in their stem. |
