Contents of caesium-137 in forest ecosystem of the locality Újezd

Abstract

1 Jihočeská univerzita v Českých Budějovicích, Zdravotně sociální fakulta, katedra radiologie a toxikologie 2 Státní úřad pro jadernou bezpečnost, Regionální centrum České Budějovice SummaryAfter the accident in the Chernobyl nuclear power plant in 1986, the area of the Czech Republic was polluted with radioactive substances. Their deposition was affected by atmospheric streaming and particularly precipitations, which supported washing the radionuclide out of the atmosphere. Further important sources are contaminants produced during nuclear weapon tests in the atmosphere. From the standpoint of long-term contamination, the most important radionuclide is caesium-137, which is absorbed by animal and plant tissues including woody species. There is a particular problem of the contamination of forest fruits and mushrooms, which are parts of the nutritional chain contaminating the meat of forest animals. The study was focused on possible association between species of mushrooms and amounts of caesium. Semiconductor gamma-ray spectrometry was used for the measurement of different species of mushrooms from a rather small area in the South Bohemian region, locality Újezd, where it was possible to assume a uniform concentration of caesium-137 in the soil. The caesium-137 activities were also measured in the wood, bark, soil and moss. The activity of the potassium-40 natural radionuclide was also measured in all the samples for comparison. The result of the measurement of the caesium-137 activity in the above mentioned components of the forest ecosystem demonstrated that these were relatively low values and their effects on the health of our population are negligible compared with other ionizing radiation sources. The subsequent contamination of mushrooms, which contaminate the meat of forest animals through the nutritional chain, is more important. The specific activity of caesium in samples of mushrooms demonstrates a considerable variation of the values measured in spite of the fact that these were mushrooms growing on a small area; similar variations were observed with the potassium-40 specific activity. The caesium-137 activity in mushrooms can be affected by the species of mushrooms, their age or possibly depth of their mycelium. SouhrnPo havárii v jaderné elektrárně Černobyl v roce 1986 došlo k zamoření území České republiky radioaktivními látkami. Jejich depozice byla určována vzdušným prouděním a hlavně srážkami, které podporovaly vymývání radionuklidů z atmosféry. Dalším významným zdrojem jsou kontaminanty vzniklé při zkouškách jaderných zbraní v atmosféře. Z hlediska dlouhodobé kontaminace je nejvýznamnějším radionuklidem cesium-137, které se vstřebává jak do živých organismů, tak do bylin a dřevin. Zejména se jedná o kontaminaci lesních plodů a hub, které pak potravním řetězcem kontaminují maso lesní zvěře. Studie se soustředila na možnou souvislost mezi druhem hub a množstvím obsaženého cesia. Pomocí polovodičové spektrometrie gama byly měřeny různé druhy hub z poměrně malého území v Jihočeském kraji v lokalitě...