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L.K. Levchuk 《Russian Geology and Geophysics》2009,50(6):562-571
The paper presents data on Callovian foraminiferal assemblages from several wells in two localities of the West Siberian plain (Shaim oil and gas district, northwestern West Siberia, and Mykhpai field, central West Siberia). The assemblages are compared and studied in terms of space and time changes of their stratigraphy, which can make basis for a more detailed zonal subdivision as more data become available. The taxonomic compositions of the assemblages are summarized in tables for specific wells to highlight their geographic variations. 相似文献
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Virginie Chapon Laurie Piette Marie-Hélène Vesvres Frédéric Coppin Claire Le Marrec Richard Christen Nicolas Theodorakopoulos Laureline Février Sviatoslav Levchuk Arnaud Martin-Garin Catherine Berthomieu Claire Sergeant 《Applied Geochemistry》2012
The diversity of bacterial communities exposed to radioactive contamination in Chernobyl soils was examined by a combination of molecular and culture-based approaches. A set of six radioactive soil samples, exhibiting high levels of 137Cs contamination, were collected from the T22 trench. Three samples were also collected in nearby soils with low contamination. Complex bacterial community structures were observed in both highly and weakly contaminated samples, using a molecular approach targeting the 16S rRNA gene. However, the presence of specific populations within samples from highly contaminated soils could not be revealed by statistical analysis of the DGGE profiles. More than 200 culturable isolates, representative of dominant morphotypes, were grouped into 83 Operational Taxonomic Units (OTUs) and affiliated to Firmicutes, Actinobacteria, Alpha-, Beta-, Gamma-Proteobacteria and Bacteroïdetes. No specific pattern linked to contamination was observed for these culturable bacteria. The results show that both highly and weakly contaminated soils host a wide diversity of bacteria, suggesting that long term exposure to radionuclides does not lead to the extinction of bacterial diversity. 相似文献
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The application of modern techniques such as infra-red absorption, mass and emission spectrometry, thin-layer chromatography and neutron activation analysis have been critically tested as a means for the identification of the geological localities of amber and other fossil resins. Thin-layer chromatography and emission spectrometry do not appear to reveal significant results. However, infra-red and mass spectrometry allow the identification of succinite, which may be geologically located in the vast area between the Black Sea, Carpathian Mountains, South Baltic, Sweden, Denmark, and Great Britain. 相似文献
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D. Bugai V. Kashparov L. Dewiére Yu. Khomutinin S. Levchuk V. Yoschenko 《Environmental Geology》2005,47(6):869-881
Several radiometric and geophysical methods were applied to characterize the subsurface geometry and radioactivity distribution (especially 137Cs) in a trench with low-level wastes at the Chernobyl site. While surface dose rate measurements and electromagnetic soil conductivity survey produced uninterpretable fields of signals, the ground penetrating radar appeared to be an efficient method for characterization of the subsurface geometry of the waste burial. It was established that the trench had the following dimensions: the length was 70 m; average width 6–8 m, and depth 2–2.5 m. Data on 137Cs distribution in the trench were obtained by means of a borehole gamma-logging technique. The total inventory of 137Cs was estimated at 600±200 GBq. Geostatistical analysis using the semivariogram function has shown regular spatial correlation patterns for the logarithm-transformed 137Cs activity of waste material. The correlation length along the trench was 17 m, while across the trench, and in the vertical direction, it was 4 m. The observed correlation patterns supposedly were caused by the method used to dispose the contaminated topsoil: the bulldozing in the direction perpendicular to a trench axis. Obtained results may be useful for selecting a characterization method and for optimization of sampling strategies for similar waste sites. 相似文献
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Field experiments and laboratory studies were performed to investigate migration processes of plutonium isotopes from a near-surface radioactive waste trench to the underlying sandy aquifer at the Red Forest waste dump in the Chernobyl zone. The objectives of these experiments were to characterize the spatial distribution and possible migration mechanisms of plutonium in the aquifer. During 2002–2007 experimental investigations were carried out and spatial distributions of plutonium isotopes (239,240Pu, 238Pu), 90Sr and major ions in the aquifer in the direction of the groundwater flow were obtained. Specific activities of radionuclides in groundwater depended on the location of the piezometer and varied in the range of 1–360 mBq kg−1 for 239,240Pu, 0.5–180 mBq kg−1 for 238Pu and n–n·104 Bq kg−1 for 90Sr. It was found that the spatial features of the distributions of plutonium and strontium specific activities in the upper eolian aquifer were similar, i.e. there was a correlation between the positions of the activity maxima of the radionuclides. The Pu isotopes plume in the aquifer spreads about 15 m downstream of the radionuclides source. Characterization of the initial radionuclide composition of the waste showed that all plutonium in the aquifer originated from the trench. The ratio of plutonium isotopes (239,240Pu/238Pu) at the sampling time was the same in waste material and in groundwater samples. In situ ultrafiltration of several groundwater samples was carried out. The size fractionation data obtained suggest that a significant part of plutonium (50–98%) in the groundwater sampled close to the source from the upper part of the aquifer is associated with a very low molecular weight fraction (<1 kDa). 相似文献
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