Microbial dechlorination of dioxins in estuarine enrichment cultures: effects of respiratory conditions and priming compound on community structure and dechlorination patterns     

Shiang Fu Q  Barkovskii AL  Adriaens P 《Marine environmental research》2005,59(3):177-195

The effect of respiratory conditions and priming compound on dechlorination patterns of heptachlorodibenzo-p-dioxins (HpCDD) was investigated using estuarine sediment-eluted cultures in the presence and absence of 20 mM sulfate, and 0.2 microM 2-bromodibenzo-p-dioxin (2-BrDD) as a priming compound. Electron balance calculations based on fatty acid turnover, hydrogen production, and electron acceptor depletion/methane formation indicated that whereas fermentative processes dominated in sulfate-free incubations, sulfate-reduction was predominant in the sulfate-amended incubations. The dechlorination of 1,2,3,4,6,7,8-HpCDD exhibited the following trends: (i) the relative yields of product formation did not exceed 30% and the presence of 2-BrDD increased the yield by up to 10%; (ii) sulfidogenic conditions resulted in a lower 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) formation, and the presence of 2-BrDD decreased the formation of 2,3,7,8-TCDD by additional 4-5-fold; (iii) the presence of 2-BrDD effected a predominance in lateral (2,3,7,8 positions) over peri (1,4,6,9 positions)-dechlorination. Denaturing gradient gel electrophoresis (DGGE) banding patterns indicated significant shifts of microbial community structure in response to terminal electron accepting processes as well as to the presence of the priming compound. The latter resulted in a similar community structure independent of dioxin spike, indicating that subsets of populations in the sediment are capable of exploiting the new niche provided by the priming compound.  相似文献   

Analysis of seawater and different highly saline natural waters by capillary zone electrophoresis     

Andrei R. Timerbaev  Keiichi Fukushi 《Marine Chemistry》2003,82(3-4):221-238

Innovative applications of capillary zone electrophoresis (CZE) to the determination of inorganic ions in environmental aquatic samples of high salinity and, particularly, in seawater are reviewed. Emphasis is placed on advanced approaches utilized for securing separation performance from being degraded by the presence of matrix salts and for simultaneous separation of ions different in natural abundance. Also covered are methodologies of present or possible use to evolve the method's practical utility to trace-level ions. Surveyed procedures are tabulated for the purpose of facilitating the method selection or further development. In addition, brief background information on basic methodological principles of CZE in inorganic ion analysis is given for a better orientation of those intending or just beginning to put CZE to work. Finally, possible future research trends and developments of CZE in the area are briefly discussed.  相似文献   

Fluxes of iron and manganese across the sediment–water interface under various redox conditions     

Svetlana V. Pakhomova  Per O.J. Hall  Mikhail Yu. Kononets  Alexander G. Rozanov  Anders Tengberg  Andrei V. Vershinin 《Marine Chemistry》2007

Fluxes of dissolved forms of iron and manganese across the sediment–water interface were studied in situ in the Gulf of Finland and the Vistula Lagoon (Baltic Sea), and in the Golubaya Bay (Black Sea) from 2001 to 2005. Fluxes were measured using chamber incubations, and sediment cores were collected and sliced to assess the porewater and solid phase metal distribution at different depths. Measured and calculated benthic fluxes of manganese and iron were directed out of sediment for all sites and were found to vary between 70–4450 and 5–1000 µmole m^− 2 day^− 1 for manganese and iron, respectively. The behavior of the studied metals at various redox conditions in the near-bottom water and in the sediment was the main focus in this study. Our results show the importance of bottom water redox conditions for iron fluxes. We measured no fluxes at oxic conditions, intermediate fluxes at anoxic conditions (up to 200 μmole m^− 2 day^− 1) and high fluxes at suboxic conditions (up to 1000 μmole m^− 2 day^− 1). Total dissolved iron fluxes were generally dominated by iron(II). Contribution of iron(III) to the total iron flux did not exceed 20%. Obtained fluxes of manganese at all studied regions showed a linear correlation (r² = 0.97) to its concentration in the porewater of the top sediment layer (0–5 mm) and did not depend on dissolved oxygen concentrations of bottom water. Organically complexed iron and manganese were in most cases not involved in the benthic exchange processes.  相似文献   

Woolly rhino discovery in the lower Kolyma River     

Gennady G. Boeskorov  Peter A. Lazarev  Andrei V. Sher  Sergei P. Davydov  Nadezhda T. Bakulina  Marina V. Shchelchkova  Jonas Binladen  Eske Willerslev  Bernard Buigues  Alexey N. Tikhonov 《Quaternary Science Reviews》2011,30(17-18):2262-2272

A nearly complete frozen mummy of a woolly rhinoceros (Coelodonta antiquitatis Blum., 1799) was discovered in a gold mine on the lower reaches of the Kolyma River, north–eastern Siberia. This is the first find of the whole body of woolly rhino in permafrost. A large part of the mummified body was preserved, including the left part of the body, covered by skin, including skin of the head and ear, fore and hind legs. The skull with 2 horns and the lower jaw were also preserved. Most of the internal organs were lost, except the intestines, stomach, and their contents. A rib fragment from this individual was dated by AMS-radiocarbon method to 39,140 ± 390 years BP (OxA-18755). Spore and pollen analyses of the stomach contents indicate that grasses and sagebrushes formed the main part of the diet of C. antiquitatis in this region of Arctic Siberia.  相似文献   

Modelling chemo‐hydro‐mechanical behaviour of unsaturated clays: a feasibility study     

Z. Liu  N. Boukpeti  X. Li  F. Collin  J.‐P. Radu  T. Hueckel  R. Charlier 《国际地质力学数值与分析法杂志》2005,29(9):919-940

Effective capabilities of combined chemo‐elasto‐plastic and unsaturated soil models to simulate chemo‐hydro‐mechanical (CHM) behaviour of clays are examined in numerical simulations through selected boundary value problems. The objective is to investigate the feasibility of approaching such complex material behaviour numerically by combining two existing models. The chemo‐mechanical effects are described using the concept of chemical softening consisting of reduction of the pre‐consolidation pressure proposed originally by Hueckel (Can. Geotech. J. 1992; 29 :1071–1086; Int. J. Numer. Anal. Methods Geomech. 1997; 21 :43–72). An additional chemical softening mechanism is considered, consisting in a decrease of cohesion with an increase in contaminant concentration. The influence of partial saturation on the constitutive behaviour is modelled following Barcelona basic model (BBM) formulation (Géotech. 1990; 40 (3):405–430; Can. Geotech. J. 1992; 29 :1013–1032). The equilibrium equations combined with the CHM constitutive relations, and the governing equations for flow of fluids and contaminant transport, are solved numerically using finite element. The emphasis is laid on understanding the role that the individual chemical effects such as chemo‐elastic swelling, or chemo‐plastic consolidation, or finally, chemical loss of cohesion have in the overall response of the soil mass. The numerical problems analysed concern the chemical effects in response to wetting of a clay specimen with an organic liquid in rigid wall consolidometer, during biaxial loading up to failure, and in response to fresh water influx during tunnel excavation in swelling clay. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Compact jets as probes for sub-parsec scale regions in AGN     

Andrei Lobanov 《Astrophysics and Space Science》2007,311(1-3):263-267

Compact relativistic jets in active galactic nuclei offer an effective tool for investigating the physics of nuclear regions in galaxies. The emission properties, dynamics, and evolution of jets in AGN are closely connected to the characteristics of the central supermassive black hole, accretion disk and broad-line region in active galaxies. Recent results from studies of the nuclear regions in several active galaxies with prominent outflows are reviewed in this contribution.  相似文献   

Population-level genotyping of coat colour polymorphism in woolly mammoth (Mammuthus primigenius)     

Claire Workman  Love Dalen  Sergey Vartanyan  Beth Shapiro  Pavel Kosintsev  Andrei Sher  Anders Gotherstrom  Ian Barnes 《Quaternary Science Reviews》2011,30(17-18):2304-2308

Patterns in the spatial or temporal distribution of genotypes may be indicative of natural selection. Previous work on the woolly mammoth melanocortin-1 receptor (Mc1r) gene identified three polymorphic positions that suggest Pleistocene populations may have harboured both light- and dark-haired mammoths (Rompler et al., 2006, 313: 62). Here, we extend this work and present the first population-level analysis of a functional gene in an extinct species. We genotyped the Mc1r gene in 47 woolly mammoth samples excavated from sites across the central portion of the woolly mammoths’ former range to examine the extent of variation of this polymorphism through time and across space. Only one individual was found to be heterozygous, indicating that the frequency of the ‘light’ mutant allele was very low. We conclude that light-coloured woolly mammoths would have been very rare, and may even have been non-existent if the ‘light’ mutant allele was strongly selected against in its homozygotic form. With the increasing availability of large-scale sequencing technologies, population-level datasets capable of identifying local adaptation will become increasingly attainable.  相似文献   

Comparison between VELACS numerical ‘class A’ predictions and centrifuge experimental soil test results     

Radu Popescu  Jean H. Prevost 《Soil Dynamics and Earthquake Engineering》1995,14(2)

The numerical ‘class A’ predictions performed within the framework of the VELACS Project are compared to the experimental results recorded in the centrifuge experiments. The comparisons are made in terms of: (1) the root mean square error of the predictions with respect to the mean of the experimental results; and (2) the size of a confidence interval centered at the predicted value which contains the estimated true value of the experimental results with a 75% probability. An assessment of the capability of various groups of constitutive soil models to predict excess pore pressures induced by dynamic loading is also presented.  相似文献   

Isoseismal map of the Vrancea earthquake of March 4, 1977     

G. Radu  V. Krník  G. Polonic  D. Prochzkov  Z. Schenkov 《Tectonophysics》1979,53(3-4)

The iaoseismal map of the intermediate Vrancea earthquake of March 4, 1977 was compiled using the contributions from many European countries within the shaken area. Characteristic features of the macroseiamic field are discussed. Mean radii of isoseismals and intensity attenuation are determined.  相似文献   

Dynamics of nonlinear porous media with applications to soil liquefaction   总被引：2，自引：0，他引：2  

Radu Popescu  Jean H. Prevost  George Deodatis  Pradipta Chakrabortty 《Soil Dynamics and Earthquake Engineering》2006,26(6-7):648-665

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