Experimental system to displace radioisotopes from upper to deeper soil layers: chemical research.
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BACKGROUND: Radioisotopes are introduced into the environment following nuclear power plant accidents or nuclear weapons tests. The immobility of these radioactive elements in uppermost soil layers represents a problem for human health, since they can easily be incorporated in the food chain. Preventing their assimilation by plants may be a first step towards the total recovery of contaminated areas. METHODS: The possibility of displacing radionuclides from the most superficial soil layers and their subsequent stabilisation at lower levels were investigated in laboratory trials. An experimental system reproducing the environmental conditions of contaminated areas was designed in plastic columns. A radiopolluted soil sample was treated with solutions containing ions normally used in fertilisation (NO3-, NH4+, PO4--- and K+). RESULTS: Contaminated soils treated with an acid solution of ions NO3-, PO4--- and K+, undergo a reduction of radioactivity up to 35%, after a series of washes which simulate one year's rainfall. The capacity of the deepest soil layers to immobilize the radionuclides percolated from the superficial layers was also confirmed. CONCLUSION: The migration of radionuclides towards deeper soil layers, following chemical treatments, and their subsequent stabilization reduces bioavailability in the uppermost soil horizon, preventing at the same time their transfer into the water-bearing stratum. (+info)
Efflux of lipid from macrophages after induction of lipid accumulation by chylomicron remnants.
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The fate of cholesterol and triacylglycerol taken up and accumulated by macrophages after exposure to chylomicron remnants was investigated using macrophages derived from the human monocyte cell line THP-1 and chylomicron remnant-like particles containing human apolipoprotein (apo) E (CRLPs) as the experimental model. In THP-1 macrophages lipid loaded with CRLPs and incubated with various cholesterol acceptors for 24 h, the mass of cholesterol and cholesteryl ester found in the cells was not changed by HDL, HDL3 or lipid-free ApoA-I, although it was decreased by 38% by ApoA-I-phosphatidylcholine vesicles (ApoA-I-PC). After loading of the macrophages with [3H]cholesterol-labelled CRLPs, only about 5% of the label was effluxed in 24 h in the absence of cholesterol acceptors, and this increased to about 10% with ApoA-I or PC only, and to about 30% with apoA-I-PC. In similar experiments with [3H]triolein, only about 4% of the labelled triacylglycerol taken up by the cells was released into the medium in 24 h, and a large (>60%) and consistent proportion of the intracellular radioactivity remained associated with the triacylglycerol throughout this period. These results suggest that cholesterol and triacylglycerol derived from chylomicron remnants are not readily cleared from macrophages, and this is likely to contribute to the atherogenicity of the remnant lipoproteins. (+info)
Disposition of 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE153) and its interaction with other polybrominated diphenyl ethers (PBDEs) in rodents.
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The disposition of the 14C-labelled polybrominated diphenyl ether (PBDE) 2,2',4,4',5,5'-hexaBDE (BDE153) was investigated in rodents following single and multiple doses and in a mixture with radiolabelled 2,2',4,4'-tetraBDE (BDE47) and 2,2',4,4',5-pentaBDE (BDE99). In single exposure studies there was little or no effect of dose on BDE153 disposition in male rats in the range 1-100 micromol kg-1. No major sex or species differences in the in vivo fate of BDE153 were detected. BDE153 was absorbed in rats or mice following gavage by approximately 70%; retained in tissues; and poorly metabolized and slowly excreted. Mixture studies indicated that, relative to each other, more BDE47 was distributed to adipose tissue, more BDE153 accumulated in the liver, and BDE99 was metabolized to the greatest extent. BDE153 was probably retained in the liver due to minimal metabolism and elimination after 'first-pass' distribution to the tissue following gavage. (+info)
Recalculation of data on 32P activity induced in sulfur in Hiroshima.
(12/60)
Historical data for 32P activity induced in sulfur by fast neutrons have been corrected for decay with a recent half-life value of 32P and recalculated with an experimentally determined efficiency ratio of the electroscope for beta rays from 32P and natural uranium used as a standard. Most samples would have been pure enough so that no correction for the weight of sulfur has been made. The possibility of interference with 32P activity measurements due to induced activity of other elements in the samples could also be excluded. The revised data show little difference from the original ones except for one sample which contained much impurity. Uncertainty of the data was also discussed. (+info)
Studies of radioactivity produced by the Hiroshima atomic bomb: 1. Neutron-induced radioactivity measurements for dose evaluation.
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This review summarizes measurements made of 152Eu and 60Co radioactivity induced by neutron radiation from the Hiroshima atomic bomb (A-bomb) with the goal of estimating the neutron dose released by the bomb. Prior to these measurements, A-bomb-irradiated specimens such as rocks and pieces of concrete, which had not been shielded were collected. The specific radioactivity obtained (in bequerels per gram of Eu or Co) were compared with those calculated from DS86 neutrons. Findings of usefulness of 152Eu data within 700 m ground range are reported and systematic differences between measured activities and calculations are discussed. The 152Eu data were also useful for the discussion of circular asymmetry, and there was no asymmetry within the experimental errors. This review also covers the similar difference found in 32P data, which were measured immediately after the A-bomb, along with the other 152Eu and 60Co data. The need for more measurements of 152Eu activity in samples farther away from the hypocenter in order to verify the DS86 calculations is also discussed. (+info)
Studies of radioactivity produced by the Hiroshima atomic bomb: 2. Measurements of fallout radioactivity.
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Three studies of fallout measurements were reviewed for the discussion of possible radioactivity intake from the Hiroshima atomic bomb. The first study discussed correlations between enriched 234U and 137Cs specific activities from the measurement of soil samples collected in the "black rain" area. The second study measured 137Cs activity on the rock and roof tile samples collected in the hypocenter area immediately after the explosion. Some of the rock and roof tile samples collected near the hypocenter had a small but detectable amount of 137Cs activity. However, it has been determined that 137Cs exposure, for example, was negligible compared with DS86 dose estimates, since these activity levels were low. The third study detected 90Sr activity in some of the specimens of human bones exhumed on Ninoshima Island. This study compared the difference in activity between the bone head and shaft, with higher activities obtained in the bone head. This fact suggests a short intake period for this activity, however, the levels of 90Sr contamination were too low to allow a discussion of the exposure risks. (+info)
A review of forty-five years study of Hiroshima and Nagasaki atomic bomb survivors. Residual radioactivity in neutron-exposed objects and residual alpha radioactivity in black rain areas.
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The residual Eu-142 radioactivity due to the atomic bomb explosion in 1945 was first found in 1976 by in-situ high resolution gamma-ray spectrometry at Hiroshima. Since then, various studies on this nuclide have continued not only in Hiroshima but also in Nagasaki and they have contributed to the reevaluation of the neutron dose due to the A-bombing. By radiochemical separation methods and alpha-ray spectrometry, rather high levels of plutonium were found in the surface soil and in the bottom sediment of water reservoir which were collected at "Black rain area" in Nagasaki. The U-234/U-238 activity ratios for the uranium leached with 0.1 HNO3 from the surface of soil samples were found to be relatively higher for the samples which were collected at "Black rain area" in Hiroshima. (+info)
Residual neutron-induced radionuclides in samples exposed to the nuclear explosion over Hiroshima: comparison of the measured values with calculated values.
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Residual radionuclides induced by neutrons from the Hiroshima atomic bomb have been measured at Kanazawa University for 14 years. The results of 152Eu, 154Eu and 60Co are reviewed in this paper. Where appropriate, an attempt is made to provide our new data with the aim of reinterpreting our published data. From the comparison of the measured values with the calculated values by DS86 methodology, we may point out here: (1) that close agreement was found between measured and calculated values for the specific radioactivity of 152Eu in the samples exposed at ground ranges between 320 m and 720 m; (2) that the calculated/measured ratios for the specific radioactivity of 152Eu were, however, larger than unity in the vicinity of ground zero and smaller than unity at locations more than 1000 m apart from ground zero; (3) that, in the vicinity of ground zero, epithermal neutron fluence evaluated from a set of measured specific radioactivities of 152Eu, 154Eu and 60Co showed a close agreement with the calculated result, whereas thermal neutron fluence evaluated in the same way was different from the calculated result; and (4) that the depth distribution of the specific radioactivity of 152Eu in a wall sample which was exposed at the location 320m from ground zero approximately agreed with the calculated result. (+info)