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1.
Summary The distribution and origin of 40K, 226Ra, 228Ra and 137Cs has been investigated in trees, mosses and lichens in the basin of the West Macedonia Lignite Centre. In tree leaves 137Cs is negligible, while the 226Ra and 228Ra concentrations are affected by the fly ash particles. Concerning 226Ra and 228Ra values of mosses and lichens, which are systematically larger than those of unpolluted areas, the application of chemometrics proved that they originate mainly from the lignite fly ash.  相似文献   

2.
This work presents the results of 137Cs, 40K, 232Th and 238U concentration (Bq kg−1) values in coastal marine sediments collected from 38 sites along the coastline of the island of Margarita, Venezuela. The purpose was to determine baseline values for these radionuclides in surface marine sediments and to detect if there were any anomalously high concentration values. Only three of the 38 sediments analyzed had measurable values above the detection limit of 0.9 Bq kg−1 for 137Cs and the highest only being 1.4 Bq kg−1. While, the concentration (Bq kg−1) ranges for the primordial radionuclides, 40K, 232Th and 238U were as follows: 12.2–211.7, <1.5–9.8 and <4.4–20.7, respectively. These concentration ranges for the primordial radionuclides can be considered as baseline values for surface marine sediments for areas that are considered not polluted by man or contaminated by nature. Finally, the concentration range of 137Cs can also be employed as baseline values, which only seem to have been the result of the atmospheric testing of nuclear weapons in the past.  相似文献   

3.
A complete methodology for 226Ra and 228Ra determination by alpha-particle spectrometry in environmental samples is being applied in our laboratory using 225Ra as an isotopic tracer. This methodology can be considered highly suitable for the determination of these nuclides when very low absolute limits of detection need to be achieved. The 226Ra determination can be performed at any time after the isolation of the radium isotopes from the analyzed samples while the 228Ra determination needs to be carried out at least six months later through the measurement of one of its grand-daughters. The method has been validated by its application to samples with known concentrations of these Ra nuclides, and by comparison with other radiometric methods.  相似文献   

4.
As part of monitoring the exposure of the Ghanaian public to natural radioactivity, radioactivity concentrations in titanium enamel frits use for coating, spraying and decorating steel bowls were investigated. Samples collected from Ghana Utensil Manufacturing Company in Ghana were analyzed using γ-ray spectrometry with a high purity germanium detector. The samples were found to contain an average absorbed dose rate of 509.38 nGy h−1, while an average annual effective dose was calculated to be 2.50 mSv.  相似文献   

5.
Concentrations of 238U, 232Th, 226Ra, 40K and 137Cs are measured in collected soil samples from various locations in the Thrace region of Turkey. The activity concentrations range from 12.82 to 101.75 Bq kg?1 d.w. (dry weight) for 238U, from 5.16 to 73.34 Bq kg?1 d.w. for 232Th, from 185.54 to 5399 Bq kg?1 d.w. for 40K and from 11.42 to 90.73 Bq kg?1 d.w. for 226Ra. In addition to naturally occurring radionuclides, 137Cs activity concentration is determined between 3.05 and 46.78 Bq kg?1 d.w. for soil samples. Determination of the radiological hazard is achieved through calculations of the external terrestrial gamma dose rate in air (nGy h?1) and annual effective dose rate (mSv year?1) and the results are compared with the similar works in different countries.  相似文献   

6.
The measurement of fission product cesium isotopes 135Cs and 137Cs at low femtogram (fg) 10−15 levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for 135Cs was 2 fg/mL (0.1 μBq/mL) and for 137Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.  相似文献   

7.
The radioactivity concentrations of 238U, 226Ra, 232Th and 40K in soil samples around Tarapur vary from 11.5 ± 2.6 to 50.3 ± 6.6, 14.9 ± 0.6 to 40.5 ± 1.2, 18.1 ± 0.4 to 75.0 ± 1.5 and 130.1 ± 1.6 to 295.1 ± 2.6 Bq/Kg respectively. The measured activity concentrations for 238U and 226Ra were compared and found in good agreement with the Indian as well as world average. The average 232Th and 40K concentrations in Tarapur were lower than the Indian average value.  相似文献   

8.
Recently, the Institute for Reference Materials and Measurements (IRMM) has assumed responsibility for organizing regular measurement comparisons among those laboratories which provide radioactivity monitoring data from their country to authorities of the European Commission (EC) under various EC legislation articles. The most recent exercise under this International Comparison Scheme for Radioactivity Environmental Monitoring (ICS-REM) in measuring the 137Cs, 40K and the 90Sr activity concentration in milk powder is presented here. The complete cycle of the comparison is described, including the establishment of reference values traceable to SI units, the demonstration of the homogeneity of the distributed samples, the treatment and measurement of samples in the participating laboratories, and the evaluation of the results.  相似文献   

9.
Distribution of 40K and 137Cs in tissues of the Citrus aurantifolia was measured by gamma spectrometry. A simple theoretical model is also proposed to describe the temporal evolution of 40K activity concentration in such tropical woody fruit species. This model exhibits close agreement with the 40K experimental results, in the leaf growing and fruit ripening processes of lemon trees.  相似文献   

10.
Radioactive decay rates are to a large extent believed to be independent of the chemical environment. This is the physics basis implicitly assumed in applications such as radioisotope dating. While this statement is a good approximation for most radioactive decays, there are cases where a slight variation of 0.5% or more can be observed, as in the electron capture type of decay. There are renewed interests in possible decay-rate changes with external parameters such as temperature, with controversy as to the phenomenon’s authenticity. In this paper, we study the variation of radioactivity counts that significantly change (up to 50% or more) with temperature. We carefully studied the characteristics of the change and found that the presence of a gaseous decay daughter can pose a serious challenge to a bona fide account of the intrinsic nuclear decay rate. After a careful solution to rate equations of the relevant isotopes under our experimental conditions, we found that most of the radioactivity change could be accounted for by the diffusion and loss of gaseous daughters under the heat, without a supposed change in the intrinsic nuclear decay rate. We hence demonstrate that an accurate determination of the decay constant has to consider the possible diffusion of volatile components in the decay chain. This is especially important in cases involving significant temperature change.  相似文献   

11.
Journal of Radioanalytical and Nuclear Chemistry - The aim of this study is to investigate the activity concentrations of 226Ra, 232Th, 40K and 137Cs in soil samples from Seydisehir and Beysehir...  相似文献   

12.
Plant uptake of radiocesium (137Cs) was investigated in consideration of the relationships with naturally existing 133Cs and potassium (K). We first determined plant-unavailable fraction of 137Cs in soil by batch sorption and sequential extraction methods with a radiotracer. Then, using the data obtained from the batch sorption and extraction methods, we clarified the relationships of plant-available and plant-unavailable fractions between 137Cs, 133Cs, and K in soil. Additionally, 137Cs concentrations in crop were estimated using 137Cs in soil and several factors, i.e. fixation ratio of 137Cs in soil, cation exchange capacity, and K concentration in crop. The results implied that the fixation ratio of 137Cs in soil was a very important key to understanding 137Cs plant uptake.  相似文献   

13.
The adsorption of Cs on clayey materials such as bentonite and Na-montmorillonite was studied in various electrolytic conditions (concentration and composition), various solid to liquid ratios and various pH conditions. The results obtained for these different conditions were modeled considering an exchange model associated to the surface complexation concept. Then, the same approach was considered to model the sorption of Rb, which have the same chemical behavior than Cs. Experiments were carried out for various electrolyte, pH, and Rb concentrations. The stoichiometries corresponding to the sorption of Rb on bentonite and montmorillonite were then deduced from the experimental results.  相似文献   

14.
Summary Transfer of 226Ra, 85Sr and 137Cs from cow and sheep milk to various Syrian dairy products has been evaluated. Dairy products include Kashkivan cheese, braided cheese, Haloom cheese, Sircassian cheese, liquid cheese, native cheese, cottage, thick yogurt, butter and milk cream. The results showed that the percentage of 226Ra, 85Sr and 137Cs transferred from cow milk to milk cream (Pt=food processing retention factor′processing efficiency′100%) has reached 32%, 16% and 7%, respectively. Butter and liquid cheese were found to have the lowest percentage of transferred 226Ra, 85Sr and 137Cs. Most of the obtained Pt values of the studied radionuclides in thick yogurt were relatively low in spite of the high processing efficiencies of thick yogurt. Moreover, the transfer, Pt, of the studied radionuclides from cow milk to the prepared cheese was higher than those values determined for sheep milk. This is due to differences in chemical compositions of each type of milk. On the other hand, the treatment of Native cheese, most commonly consumed cheese in Syria, with different concentrations of NaCl solutions showed that 137Cs was completely removed from cheese soaking in 5% NaCl solution (soaking time of 48 hours), while 40% of 226Ra and 80% of 85Sr were also decontaminated using 0-2.5% NaCl solutions and soaking time of 48 hours. Based on the obtained results, industrialization processes of the dairy products that resulted the removal of radionuclides have been identified.</p> </p>  相似文献   

15.
The phosphate rocks used for the production of phosphate fertilizers present in their composition radionuclides of the U and Th series. During the chemical attack, the radionuclides are distributed to final products and phosphogypsum. A sequential radiochemical procedure was implemented to determine the content of radionuclides alpha emitters in samples of fertilizers and phosphogypsum produced in Brazil. The results obtained show that the levels of radioactivity present in the fertilizers are of the same order of magnitude on those found in the phosphogypsum, reaching values up to 1158 and 457 Bq kg−1, for the U and Th series, respectively.  相似文献   

16.
Inventories and fluxes of 210Pb, 228Ra and 226Ra were determined in sediment cores collected at nine stations covering of the southern South China Sea and Malacca Straits with the thickness of water column between 42 and 83 m depth. The inventories of 210Pb, 228Ra and 226Ra were calculated range from 0.15–2.55 Bq cm−2, 0.05–0.40 Bq cm−2 and 6.83–83.63 Bq cm−2, meanwhile the fluxes ranged from 0.005–0.079 Bq cm−2 yr−1, 0.009–0.048 Bq cm−2 yr−1 and 0.003–0.037 Bq cm−2 yr−1, respectively. The results show that the highest inventories and fluxes for 210Pb, 228Ra and 226Ra were found at station WC 01 and EC 05. Because there are additional sources of 210Pb, 228Ra and 226Ra, where water transport will brings more dissolved isotopes, influence of the transportation and deposition of suspended particles, fast rate of regeneration and greater production of those radionuclides and others.  相似文献   

17.
Cesium-137 distribution in several rivers, lakes and their sediments was investigated with HPGe detectors to elucidate the source of this isotope in some fresh waters from Kashiwazaki-Kariwa area, Niigata, Japan. It was suggested that there exists a place abundant in fallout radionuclides in the east side of a mountain which is located by the coast. Great westerly monsoon will contribute significantly to this phenomenon, which seems to be characteristic of mountains along the Sea of Japan.  相似文献   

18.
More than one hundred undisturbed soil samples from Northern Venezuela and the islands of Margarita and Los Roques have been analyzed for137Cs,40K,238U and232Th by -ray spectroscopy. The specimens were taken from between 5–10 cm below the earth's surface. Thus, they are valid not only for the137Cs deposition studies but also for the estimation of the natural -ray dose from primordial radionuclides that form the terrestrial component. The concentration of40K was directly determined from its 1461 keV -ray, while those of137Cs,238U and232Th were performed using a -ray from one of their daughter radionuclides: the 661 keV -ray of137mBa for137Cs, the 1760 keV -ray of214Bi for238U and the 2620 keV -ray of208Tl for232Th. Finally, the concentration values were compared with those of global estimates.  相似文献   

19.
The analysis of 226Ra in natural waters can be tedious and time-consuming. For the determination and differentiation of activities of 226Ra and 222Rn in drinking water by γ-ray spectrometry a simple and fast method is presented. Activities of 226Ra > 0.5 Bq L−1 can be determined according to stabilization of the sample without further procedures. For a more sensitive detection sample volumes of up to 5 litres are applicable by a rapid precipitation procedure without large expenditure. Further laborious enrichment methods are not necessary. Thus, detection limits of 0.1 Bq L−1 can be obtained when using sample volumes of 5 litres. Therefore the method is suitable for the monitoring of radioactivity in drinking water samples in accordance with the legal guidance of the European Union.  相似文献   

20.
Summary The amount and dislocation of the gamma-radionuclides (artificial cesium and natural potassium) in the Haplic podsol profiles of the Tatra Mountains have been described. These soils belong to the group of penetrable formations what is a result of their texture. They provide a good example of percolation and sorption possibilities of the radionuclides within the soil profile. The highest concentration of radionuclides has been detected in raw humus and spodic (illuvial humus-iron) layers, at the surface.  相似文献   

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