Results 1 - 10 of 7427
Results 1 - 10 of 7427. Search took: 0.027 seconds
|Sort by: date | relevance|
[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] 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] 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] 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] Transfer coefficients for radiocaesium transport from a sheep's diet to blood, muscle, lung, liver, kidney, spleen heart, brain, rumen, intestines and fat were measured in a controlled experiment involving 50 adult ewes. The animals were fed dry grass and wheat, both contaminated with Chernobyl fallout debris, for a period of 60 days. During this period half of the animals were killed at regular intervals and samples of their blood and tissues were measured for radiocaesium concentration. The rest of the animals were returned to uncontaminated food and were monitored for radiocaesium concentration through periodic slaughtering for an additional 60 days. Transfer coefficients were extracted from the plateau reached at the end of the contamination phase. The data were also analyzed by means of a recently proposed linear multiple compartment model and transport rate parameters for each compartment were extracted. Transfer coefficients computed through the model's transport rate parameters show remarkable agreement with the experimentally obtained values. (author)
[en] In 1986 a large number of farms in the Chernobyl-affected area in the county of Västernorrland in northern Sweden were investigated for radiocaesium transfer to grass and cereal grain. The soil surface layer (0-5 cm) in 1986 and the crop products in 1986-1996 were analysed. The aim was to study the impact of soil and crop rotation on sensitivity of 137Cs transfer in a short and long term perspective. In the fallout year 1986 the transfer to grass was usually much higher than to cereal grain. In this year the transfer to grass was usually much higher in the first cut rather than the second cut. The reduction in transfer with year was large but variable with site and with crop sequence. Ploughing was effective in decreasing the transfer of 137Cs to crops. On arable sites in 1986 the transfer to cereal straw was larger at late stem elongation (LSE) than at the maturing stage. Unexpectedly, there was no clear relationship between transfer of 137Cs to the crops and any of the soil characteristics. In 1986 the transfer of 131I to grass and cereals was also investigated on some of the farms. The results are compared with the transfer of 137Cs, 2 months after the Chernobyl fallout
[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] 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