|
|
The evaluation of 137Cs content in mushrooms and forest berries in the South Bohemia region
HÁLOVÁ, Jana
The collection and consumption of forest fungi and blueberries are among the most popular seasonal activities in Czech Republic. Due to the Chernobyl accident, however, these raw materials are believed to have contained increased amounts of radionuclides. The aim of the work is to evaluate the content of 137Cs in blueberries and fungi collected from South Bohemian region in the period of 1992 - 2020. Data of 137Cs mass activity obtained from the State Office for Nuclear Safety's MonRas database were re-examined for validation using samples of fungi (n = 318) and blueberries (n = 142). The results ranged widely as follows: (a) boletes fungus, from 0.18 to 6430 Bq / kg; (b) leafy fungus, from 0.28 to 4040 Bq / kg; and (c) blueberries, from 0.24 to 2046 Bq / kg. Between boletes fungus and leafy fungus, the former was seen to have a higher ability to accumulate the radionuclide 137Cs. The calculated effective dose caused by the consumption of fungi and blueberries was assessed as negligible, amounting only to less than 1% of the general limit for the population. Despite these favorable results, detailed monitoring of raw materials from nature needs to be continued and the safety of the food chain ensured.
|
|
|
The influence of trees on contamination of soil with 137Cs
TRNKOVÁ, Michaela
Nuclear weapons testing in the atmosphere and accidents in nuclear energy facilities in the last 50 years caused significant contamination of the environment. Half-life of certain leaked radionuclides is several decades and therefore they are still present in today's environment. That is the reason why there is still on going monitoring of radiation situation in the Czech Republic in order to determine the behaviour and kinetics of anthropogenic radionuclides in the environment and the severity of radiological impact on humans. The results of this monitoring serve to review the radiation situation, observe long-term trends and last but not least to gain new knowledge that could facilitate the management od radiological emergencies. The aim of this thesis was to measure the content of 137Cs in soils under and around leafy tree crowns in the area affected by radiation fall and to find out whether the tree's crown has an effect on the distribution of 137Cs in the soils below them. To this end, a research question has been set: Do tree crowns affect the distribution of cesium in the soils below them? For better intelligibility, the introduction of the thesis is devoted to information about ionizing radiation, basic terms and quantities in the field of ionizing radiation, sources of radionuclide contamination, especially the Chernobyl nuclear power plant accident, environmental and population contamination, and elements important for the practical part of this work. The theoretical part is followed by research methodology. The soil samples were collected under five leafy trees of the Walnut species that met the set criteria for collection. Under each tree, samples were taken in three directions at an angle of 120° always at the trunk, in the middle of the crown, at the edge of the crown and outside the crown. Thus, 12 samples per tree, a total of 60 samples. Dry and purified soil samples were measured by semiconductor gamma spectrometry which determined 137Cs radionuclide mass activity values as well as naturally occurring radionuclide40K. Graphs were generated from the measured values. Despite the frequent deviations that may be caused by natural phenomena or human activities, it was found out that tree crowns affect the distribution of 137Cs in the soils below them.
|
|
|
Correlation of Cs - 137 content between soil and sponge Deer truffle
DŽURNÝ, Vladan
In recent years, the issue of increased contamination of Cs-137 wild boar meat has come to the fore. One of the dominant agents of this contamination is Deer truffle because of its ability to accumulate Cs-137 in large quantities. The so-called transfer factor (hereinafter referred to as "TF") allows us to assess the ability of Deer truffle to absorb Cs-137. The aim of this work is to measure TF Cs-137 in the fungus Deer truffle and compare it with TF for other fungi. In order to calculate TF, the weight activity of Cs-137 in the individual samples was determined (Deer truffle and the soil in which it was found). The Cs-137 mass activity was measured in the laboratory of the SÚJB Regional Center in České Budějovice using the HPG gamma detector and subsequently determined in the Gamwin program. A total of 6 samples from the South Bohemian Region were measured. The highest measured value of Cs-137 activity was found in Okrouhlá I (soil: 105 Bq.kg-1), (Deer truffle: 2030 Bq.kg-1). The largest calculated TF = 19.3 (Okrouhlá I) was compared to the TF of 26 fungal species from the selected publication. A very strong correlation was found between the amount of Cs-137 in the soil and the Deer truffle. The observed TF is significantly greater than the TF of the compared fungi. The strong correlation and significant TF value represent the potential of Deer truffle to absorb much larger amounts of Cs-137 than the fungal species compared, confirming the work hypothesis. The results of the work can help to clarify the origin of the high content of Cs-137 in the meat of wild boars and can also provide a basis for further investigation of this issue.
|
|
|
The Cs-137 content in wild game
HÁKOVÁ, Veronika
The surrounding world has been influenced by ionizing radiation ever since. From the beginning they were only the natural sources as cosmic and solar rays or earth's radiation. Technical development of society brought discovery of artificial sources of ionizing radiation. In the beginning scientists studied them with noble aims. Eventually the negative side of utilization of nuclear fission was discovered in nuclear weapons. Artificial sources of ionizing radiation are mainly nuclear weapon's testing products from fifties and sixties in last century and nuclear power plant's accidents' products. When it comes to environment's contamination by Cesium radionuclide Cs-137 (further only Cs-137) and by inhabitants influencing, in The Czech Republic territory the biggest effect came from Chernobyl nuclear power plant failure. The aim of Bachelor Thesis is comparison of Cs-137 amount in meat of some species of forest or wild animals by semiconductor gamma spectrometry. The research question is whether amount of Cs-137 depends on animal species, or not. In The Thesis's introduction the general findings concerning ionizing radiation are described. What actually the ionizing radiation is and what a radionuclide and a half-life are. The next is a short set of quantities coming with ionizing radiation. Whereas the amount of Cs-137 in wild animal meat is examined, next part deals with Cesium and its isotope Cs-137. The amount of Cs-137 is very often compared with amount of natural Potassium K-40 (further only K-40) which is one of the most widely spread radionuclide in environment. Other part of The Thesis is devoted to nuclear weapon development. It actually began in between World Wars in the beginning of 20th century. The second most significant source of Cs-137 in our area was the crash of the 4th reactor of nuclear power plant Chernobyl, which occurred on April 26, 1986. By the way in this year has passed 30 years from one of the biggest nuclear catastrophe ever. In the next part a summary of wild animal species is given. Such animals were ahead selected and their meat was used as samples for measurement of Cs-137 mass activity. Mass activity was measured by means of semiconductor gamma spectrometry in Regional Centre of State Office for Nuclear Safety in České Budějovice. Due to availability of game animals was chosen Jindřichův Hradec region. Samples available for measurement reason were taken from the following kinds of hunting game: wild boar, fallow deer, roe deer, fox and hare. From each, under permission hunted piece was taken specimen of about 500 grams. After cleaning and cutting meat vas put to special Marinelli measurement bowls and frozen. Later was measured Cs-137 mass activity and for comparison also K-40 one. Measured values of Cs-137 mass activity oscillated from 1,9 Bq.kg-1 to 191 Bq.kg-1. In both cases it was meat of wild boar. Figures K-40 mass activity were from 47,4 Bq.kg-1 up to 201 Bq.kg-1. Where the lowest value came from meat sample of wild boar, then the highest value came from meat sample of roe deer. The numbers of Cs-137 and K-40 mass activities in meat sample of fox were almost the same. The mass activity values of any sample never reached the threshold value 600 Bq.kg-1, which is given by Announcement about radiation protection no. 307/2002 Sb. Measured values shows that amount of C-137 vary with the type of wild animals. According to statistic data the average game consumption is 700 grams per adult per year. In case of our family the consumption is even 7 200 grams per adult per year. Just for interest was calculated committed effective dose for consumption of 700 grams and also for estimated consumption of 7 200 grams. With consumption about 700 grams per adult per year the committed effective dose is 0,0017 mSv and with consumption about 7 200 grams is 0,018 mSv. The result is - effective dose values are not of great significance, contamination of hunting game meat by Cs-137 is
|
|
|
The contents of caesium-137 in different soil types in selected locations in CR
ČADOVÁ, Michaela
Caesium-137 is one of the major artificial radioactive elements, whose sources are atmospheric nuclear tests carried out in the 20th century and nuclear power plant incidents such as Chernobyl. Because of uneven precipitation, there were significant differences in radioactive fallout levels in different areas of the Czech Republic during the passage of the radioactive cloud from Chernobyl. Due to the high solubility of Caesium-137 in water and easy distribution in the environment, there is contamination of the lower soil levels where the plant root systems are located. The aim of this work is to collect soil samples from selected localities, where in 1986 significant contamination was detected as originating from Chernobyl, determination of their Caesium-137 content by gamma semiconductor spectrometry and comparison depending on the type of soil. The research question was set as: Does Caesium-137 content differ in different soil types? As part of this study, samples of uncultivated agricultural land and forest land were collected from layers 0-5, 5-10 and 10-15 cm in Kvilda, Zadov and Churanov. For comparison, results were also collected from a locality where the radioactive fallout was not so significant. This locality is around the village Straz nad Nezarkou, which is found on the protected nature reserves of Trebon. From the results of measuring the soil it was found that even after thirty years since the Chernobyl disaster occurred, Caesium-137 is still found in the upper layers of soils, specifically to depths of 5 cm. The highest specific activity of Caesium-137 was measured in the forest soils in Zadov at depths of 0-5 cm (364 Bq.kg-1) from the total range of all samples, 2,24 Bq.kg-1 to 364 Bq.kg-1. The highest specific activity of potassium K-40 was measured in uncultivated agricultural land in the locality of Kvilda at depths of 0-5 cm (883 Bq.kg-1).
|
|
|
The Cesium-137 content in wild game in Šumava.
VENČOVSKÁ, Petra
Our territory was the artificial radionuclide cesium-137 (hereafter 137Cs) contaminated by radioactive contamination during nuclear testing in the atmosphere and to the largest nuclear accident occurring in Chernobyl. Contamination of the environment and its components 137Cs is still being monitored due to the long half-life of this radionuclide. The stated goal of the work is to compare the mass activity of 137Cs in the forest species from the Šumava region. This also results in the research question as to whether there is a difference in 137Cs in the mass of different animal species living in forests in the Šumava region. According to the availability of samples, the administrative districts of Vimperk and Horní Planá were selected. From these localities, there are also 14 measured samples of fur animals, which were provided for this research. Consequently, the content of 137Cs was determined by gamma semiconductor spectrometry, which, besides mentioned 137Cs, was also used for comparison with potassium-40 (hereinafter only 40K), which is the most widely used natural radionuclide. The measurement results also show that higher concentrations of 137Cs were in samples from the Vimperk region, and also that higher mass activity of 137Cs was measured in herbivores. The highest value of 40K was measured in both herbivores and omnivores. Effective dose ranges were calculated from the results obtained to express the level of contamination that would occur in the case of the consumption of contaminated meat. Calculated values of effective dose ranges due to internal contamination as well as other sources of radioactivity are not significant and their effect on the health of our population is negligible.
|
|
|
Comparison of the measured specific activities of cesium 137 in different species of bryophytes.
TRNKOVÁ, Michaela
This bachelor thesis focuses on measuring specific activities of Cs-137 in different species of moss in areas affected by radiation fallout and compares the species different tendencies to absorb radionuclides. The research question is: Do different species of moss in areas affected by radiation fallout contain different amounts of Cs-137? The theoretical part of the thesis introduces the radiobiological problematics, including basic terms and units, and its contemporary situation. This part also focuses on radionuclide Cs-137 and its sources and kinetics in nature. The practical part describes used methodology and consequently focuses on the results of measuring chosen moss samples, including their subsoils. Specialised literature describes mosses as significant bioindicators of radionuclides. This thesis tries to distinguish different species and establish whether those different species have different tendencies to absorb radionuclides. The locations for sampling were chosen according to previous studies which located areas with high concentration of Cs-137 caused by radiation fallout in 1986. The total amount of moss and subsoil samples is 20 samples each. One of the locations was Russian island Valaam in Ladoga Lake where four samples were collected. Specific activity was measured using semiconductor gamma spectometry. Beside Cs-137, the focus was on concentration of natural radionuclide K-40. Measured spectra were evaluated by GAMWIN software. Measuring specific activity of Cs-137 in moss and subsoil samples and calculation of transfer ratio proved that different species of moss in areas affected by radiation fallout contain different amount of Cs-137.
|
|
|
Contents od caesium-137 in mushrooms
ČADOVÁ, Michaela
The aim of this work is to compare the presence of Cs-137 in different kinds of mushrooms in selected locations using semiconductor gamma-ray spectrometry. Research question was determined: Does Cs-137 content amount vary depending on the fungal species? The first part deals with basic knowledge of ionizing radiation, which is important for the complex understanding of thematic problems. This concerns basic radiobiological terms such as radioactivity, ionizing radiation, its biological effects and basic units and quantities used in radiobiology and radiation protection. Further I deal with the above mentioned measured radionuclide Cs 137, which resources in our country include the Chernobyl nuclear plant accident and tests of nuclear weapons in the 20th century. I also pay attention to this element in the cycle of nature, its distribution in the body and the effects on our environment. Shortly I even deal with basic knowledge of the Cs-137 accumulation in mushrooms. Another point mentioned is the research methodology, a brief introduction to semiconductor gamma spectrometry. As sampling sites I selected Zadov, Churáňov and Kvilda in Šumava, where in 1986 there was detected the biggest radiation fallout. For comparison, I also measured samples of mushrooms from localities of less significant fallout. These are sites around a village of Příbraz and in the woods of Jemčina within Třeboň region. A total of 26 mushroom samples were taken. Mass activity was measured by semiconductor gamma spectrometry in the Regional Center of the State Office for Nuclear Safety in České Budejovice. In addition to Cs 137 there was also measured a content of a natural isotope Potassium-40. It is a Cs 137 chemical homologue, which has similar properties and is present homogeneously throughout the whole ecosystem. For comparison I also measured mass activity of other forest ecosystem components such as moss, bark, cones and ground. Measuring time of the mushroom samples was for about 24 hours. The other forest ecosystem components measuring time ranged from 24 to 48 hours. The measured spectra were analysed by using the GAMAT software tool. The highest measured mass activity of Cs-137 was detected in a pine bolete sample from the site of Churanov in Sumava (4 265 Bq.kg-1). Also Russula emetica from Zadov shows relatively high activity (3 050 Bq.kg-1). The smallest amount of Cs 137 was measured in Cystolepiota high, originating in the locality of Jemčina in Třeboň region (5.6 Bq.kg-1) and in a sample of Lactarius volemus from the nearby village Příbraz (34.7 Bq.kg-1). The highest mass activity of natural radionuclide K-40 was measured in a sample of blusher from the village Příbraz site (4 329 Bq.kg-1). High value was probably caused by the use of fertilizers or pesticides near this sample. Large number of K-40 was also seen in Laccaria amethystina, also coming from the village Příbraz (2 901 Bq.kg-1). On the contrary, the least of this element was found in Cystolepiota high sample from Jemčina forests (971.8 Bq.kg-1) and in Lactarius volemus from Příbraz (999,6 Bq.kg-1). According to the measured values, we can conclude that the measured mass activity differs a lot. Individual sites may have different values because of uneven rainfalls in our country at the time of the radioactive cloud passage after the Chernobyl explosion. However, specific species of fungi from the same sites differ, which is due, inter alia, to soil characteristics and mycelium depth. The results correspond to the fact that the mushroom-shaped fungi show a greater amount of Cs-137 unlike gilled fungi presented as well by other authors.
|
guest ::
