Results 1 - 10 of 3996
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[en] This work provides new insights into the presence of 239Pu, 240Pu, 241Pu, and 236U in the Southern Hemisphere through the study of peat bog cores from marshlands in Madagascar (19°S). 210Pb, 238Pu and 239+240Pu activities were characterized by alpha spectrometry in previous studies. Here, Pu from alpha-spectrometry discs corresponding to 10 peat-bog cores (85 samples) was reassessed for the aim of completing its isotopic composition (239Pu, 240Pu, and 241Pu) by Accelerator Mass Spectrometry. In addition, 236U was studied in a single core exhibiting unusually low 240Pu/239Pu ratios. Integrated 240Pu/239Pu atom ratios in the single cores ranged above and below the (0–30°S) fallout average ratio, 0.173±0.027, from 0.126±0.003 to 0.206±0.002, without a regional pattern, thereby demonstrating the heterogeneous distribution of the 239Pu and 240Pu signal. However, such a variability was not observed for 241Pu/239Pu, ranging from (6± 1) · 10−4 to (11 ± 1) · 10−4 and consistently below the (0–30°S) fallout ratio of (9.7± 0.3) · 10−4 (2012). The integrated 236U/239Pu atom ratio in the studied core, 0.147 ± 0.005, was also significantly lower than the values reported for the global fallout in the Northern Hemisphere, in the 0.20–0.23 range. Our results point out to stratospheric fallout as the main source of both 236U and 241Pu at the studied site, whereas 239Pu and 240Pu signals show the influence of tropospheric.
[en] Specific activity of 137Cs, 40K, and 210Pb radionuclides in fifteen selected medicinal herbs from three locations in Central Serbia (two mountains, Kopaonik and Zlatar, and a valley, Sokobanja) was measured using two semiconductor HPGe spectrometer systems. The obtained values are in intervals (<0.3 ÷ 9.7) Bq/kg, (<0.2 ÷ 24.7) Bq/kg, and (<0.2 ÷ 5.7) Bq/kg for 137Cs; in intervals (125 ÷ 1100) Bq/kg, (104 ÷ 872) Bq/kg, and (103 ÷ 954) Bq/kg for 40K, and in intervals (3.6 ÷ 49.0) Bq/kg, (3.9 ÷ 57.9) Bq/kg, and (2.8 ÷ 103) Bq/kg for 210Pb, for herbs from Kopaonik, Sokobanja and Zlatar, respectively. The highest activity measured in individual herbs was: 24.7 Bq/kg for 137Cs (Sokobanja valley), 1100 Bq/kg for 40K (Mt. Kopaonik) and 103 Bq/kg for 210Pb (Mt. Zlatar). The corresponding individual annual effective doses due to ingestion calculated from the measured activity concentrations, of the radionuclides are: in intervals (<1.7 ÷ 82.9) nSv, (<1.4 ÷ 211) nSv, and (<1.1 ÷ 48.7) nSv for 137Cs; in intervals (0.76 ÷ 4.5) μSv, (0.64 ÷ 4.4) μSv, and (0.63 ÷ 4.9) μSv for 40K, and in intervals (1.1 ÷ 18.2) μSv, (1.3 ÷ 21.6) μSv, (0.9 ÷ 38.3) μSv for 210Pb, respectively. The specific activity concentration values of 137Cs and 40K obtained for the investigated herbs are similar to the literature data, while no information was found in literature about specific activity concentration of 210Pb. The all values obtained for individual annual effective dose due to ingestion are less than 100 μSv, which means that the daily use of 200 mL of herbal infusion during a year made from the investigated herbs does not represent a radiological risk for health. However, a high individual annual effective dose of ingestion of 210Pb obtained for some herbs indicate that their consumption in larger amounts 2–3 cups of infusion daily over a year could make the dose to exceed the recommended level, and points to necessity for extensive investigation of 210Pb activity concentration worldwide. © 2019 Elsevier B.V.
[en] Soil ingestion as a source of radiocaesium contamination to ruminants was studied by measuring the transfer coefficient to sheep milk. Eight lactating ewes, housed in individual metabolism cages, were used. Fifty grams per day of heavily contaminated sandy topsoil, collected in 1990 from the Chernobyl area, were administered orally to the animals for a period of 1 week. The daily dose intake in 137Cs was 1835 Bq day−1. During this contamination period, daily milk production and excreta output were measured. The ewes were monitored for an additional 7 day decontamination period, while they fed on uncontaminated feed. Transfer coefficients were obtained through a best fit (minimum χ2) of the data to predictions of a linear compartment model. The values obtained were fm = (2.6 ± 0.7) × 10−2 and fu = (5 ± 2) × 10−2 days kg−1 for radiocaesium transport to milk and urine, respectively. These results suggest that soil ingestion can be a major source of radiocontamination for sheep and other free-grazing ruminants. Comparison of our results with soil-to-milk transfer coefficient values derived in two recent independent experiments suggests that there might be a strong dependence of radiocaesium availability on soil composition. (author)
[en] The results of a 5-year investigation on the radioactive contamination of mushrooms are presented. More than 400 samples of various mushrooms species have been examined for γ-emitters. Some samples have also been analysed for strontium-90 and plutonium isotope content. Maps of caesium-137, caesium-134 and potassium-40 activities, based on the measurements of 278 samples of Xerocomus badius collected in 1991 throughout Poland are presented. The highest measured activity of caesium-137 was 157 kBq/kg dry mass (Xerocomus badius). A dosimetric interpretation of the observed contamination levels is proposed
[en] The sampling procedures in connection with a very sensitive analytical method are described. Results from different areas in Austria are presented and an interpretion of the results is attempted. Some findings are in accordance with measurements from other substances, some are not. The differences most probably depend on several factors like soil type, precipitation, migration of strontium-90, concentration of stable strontium and calcium. No significant rise in the concentration could be found after 1986 thus in accordance with other measurements of strontium-90 contamination after the Chernobyl accident
[en] This paper gives an overview of pre- and post-Chernobyl technical approaches to decontamination of terrestrial environments in the territories of the former USSR with special emphasis on the effectiveness of mechanical and physical countermeasure techniques. Descriptions of these techniques (removal of vegetation, removal of soil and ploughing) is preceded by a short summary describing various characteristics of the fallout deposited on the areas around the Chernobyl NPP and the radionuclide distribution and migration in soils, which helps to place the techniques described in context. Management of radioactive wastes resulting from decontamination operations conducted on a large scale, such as those related to the Chernobyl accident, appears to be the most complex problem and has been given particular attention in this paper. Four of the projects most relevant to this particular aspect are discussed. They include the development of new methods for the decontamination of soil based on deep ploughing, studies of the potential of geo-electrochemical decontamination of soil, research and development on prevention of radionuclide migration with infiltration run-off from soil by placing a sorbing layer under the contaminated layer of soil and the ‘Vector’ project to build a facility for treatment and disposal of radioactive wastes generated by various decontamination procedures
[en] A powerful analytical method for simultaneous determination of 63 pharmaceuticals and some metabolites in aqueous samples has been developed. The list of compounds amenable to the methods includes different therapeutic classes belonging to antibiotics, stimulants, antidepressants,mucolytics, and antiparasites. The method involves concentration and clean up by an offline solid phase extraction SPE followed by liquid chromatography coupled to tandemmass spectrometry (LC-ESI-MS/MS). The recovery of the target compounds from water samples was most efficient onWaters Oasis HLB SPE cartridge, while acetonitrile/water (60/40)was shown to be the most suitable solvent for desorbing the compounds from SPE. In addition, acidification of samples prior to SPE was optimized to enhance the recovery of the compounds. In terms of method validation, the recoveries of analytes ranged from 68% to 134%. Repeatability and intermediate precision were b11% and 14%, respectively. The method detection limits ranged from 2.3 ng L-1 to 94.3 ng L-1. An optimized method was applied in a monitoring program to study the occurrence of pharmaceuticals to more than hundred samples collected from rivers, lakes, fountains, and wells overall Lebanon from April to June 2016. Caffeine, erythromycin and its degradation forms,were themost frequently detected compounds at levels reaching N10,000 ng L-1 and 2000 ng L-1, respectively. Moreover, bacterial analysis showed that the samples were contaminated by Escherichia coli (23%), intestinal Enterococcus (48%) and Pseudomonas aeruginosa (27%). Therefore, in order to evaluate if a correlation exists between finding antibiotics in water samples and the development of resistant-bacteria, an antimicrobial susceptibility test was conducted to the identified isolates using disk diffusion method. Multiple-antibiotic-resistant. (author)
[en] The feasibility and efficiency of agrotechnical countermeasures are discussed, which may be applied before and during the deposition of radioactive fallout. As preventive measures in case of an impending radioactive contamination, different suggestions are made, such as, harvesting as quick and as many mature crops as possible, covering vegetables grown out of doors and perhaps fruit crops with impermeable foils, as well as covering open feed and food stores, thus entirely preventing contamination of these crops. Grazing ruminants may be stalled or driven into makeshift enclosures to prevent them from grazing during and after deposition. The feasibility of these measures is mostly time dependent, but also confined by the available capacity of foils, machinery and manpower. At the beginning of dry and wet deposition the advantages in limiting deposition on crops or the grazing of contaminated pastures by domestic animals must be weighed against the cost, including occupational hazard of the farmer working outside. Further measures which could be applied during and/or shortly after deposition are preventing domestic animals from drinking rainwater or other surface water resources. In some circumstances it may even be appropriate to ban the use ocontaminated water for spray or sprinkler irrigation of vegetables and other crops. It is finally stressed that the essential prerequisite to these measures is an efficient early warning system which should operate on an international scale
[en] After the Chernobyl nuclear reactor accident in April 1986, 137Cs was found to be one of the most abundant radionuclides released and the forest ecosystem was one of the most contaminated environments. Long-term management of the forests to minimize the radiation dose to man requires understanding of the cycles of the 137Cs and the other radionuclides which were also deposited. Thus, the health physicists responsible for remediation programs in the contaminated zones must have information on the long-term behaviour of the deposited radioactivity. The similarity between the chemical properties of Cs and K and the fact that K has been studied previously as a nutrient in forest productivity may provide an analogue to evaluate the long-term mechanism of the deposited radioactivity. One of the goals of this study is to describe the global cycle of K in forests related to the 137Cs contaminant. The first results of an experimental program to measure the deposition of 137Cs in the several forest compartments is presented, together with the complementary K results. These data provide information which is necessary to construct a useable model describing the 137Cs-transfer after atmospheric contamination of a woodland ecosystem
[en] A long term-low level exposure (LLE) experiment was conducted on rats to determine the metabolic patterns for realistic dietary levels of cadmium. Male rats fed with 61 ppb of cadmium ad libitum, 50 labelled with 109Cd radiotracer as cadmium chloride via drinking mineral water and 11 unlabelled via food for 2 years. The diet was characterized in its metal content by neutron activation analysis to obtain the total dietary intake of different elements. The kidney was found to be the tissue with the major concentration of cadmium which accumulated continuously during the experiment. The variation of the accumulation pattern of Cd concentration in the liver and intestine indicated an initial rapid increase of Cd during the first 100 days. After this period an apparent equilibrium was attained in both these tissues until the end of the study. The intracellular distribution of cadmium in kidneys, liver, intestine and pancreas were similar, the cytosol fractions containing about 80% of the cellular cadmium. Dialysis experiments indicated that significant amounts of cadmium were able to be associated with cellular organelles, the mitochondria representing the most important organelle capable of binding cadmium. The cytoplasmatic Cd-profiles obtained at various stages of the experiment showed that the metal was only bound to a low-molecular-weight component, cadmium-binding protein (CdBP), which represents the specific cellular-binding component for cadmium under the long term-low level exposure (LLE) conditions. No significant variations in the concentrations of the elements in different organs were observed in animals supplemented with 109Cd in respect to 109Cd untreated controls. (Auth.)