Physico-chemical and biological sediment properties determining erosion resistance of contaminated riverine sediments – Temporal and vertical pattern at the Lauffen reservoir/River Neckar, Germany     

Sabine Ulrike Gerbersdorf  Thomas Jancke  Bernhard Westrich 《Limnologica》2005,35(3):132-144

In order to contribute to a reliable, easy-to-handle and economically viable erosion risk assessment of contaminated riverine sites, the present study aims to implement master-variables best characterising the sediment stability. Thus, a wide range of sediment properties was related to the critical shear stress for mass erosion, determined in the SETEG (Stroemungskanal zur Ermittlung der tiefenabhaengigen Erosionsstabilitaet von Gewaessersedimenten) pressurised channel, with special emphasis on vertical and temporal gradients in the Lauffen reservoir on the River Neckar. Over the course of 1 year, positive impacts of some macrofauna species and benthic diatoms on the sediment stability were detected for the sediment surface (0.5 cm). However, a high seasonal variability of biological parameters caused varying relations with erosion resistance in the upper sediment layers as shown for the colloidal carbohydrates. Considering only deeper sediment layers (5–35 cm), a more general pattern could be revealed with correlations between the critical shear stress and single sediment properties such as depth, grain size, total organic carbon (TOC), cation exchange coefficient (CEC), carbohydrates and proteins. Firstly, the influence of physico-chemical and biological properties on erosion resistance became evident, even over depths at 0–35 cm. Secondly, inter-particle forces are most important for erosion resistance. These are enhanced in fine-grained sediment layers, offering high binding capacities but also strengthened by polymeric substances permeating the void space and coating particles. These covariance patterns of sedimentological and biological parameters are addressed by multivariate statistical tests (principal component analysis), resulting in a higher magnitude of the correlation coefficient between critical shear stress and the master-variables in main component II (polymeric substances, grain size, TOC, CEC; R=0.77) compared to single correlations.  相似文献   

Thermal effects in partially saturated soils: a constitutive model   总被引：1，自引：0，他引：1  

Gabriella Bolzon  Bernhard A. Schrefler 《国际地质力学数值与分析法杂志》2005,29(9):861-877

The present paper is centred on the assessment of an elastic–plastic model for partially saturated soils, earlier proposed by the authors, for its predictive capability with respect to temperature changes, on the light of available experimental results. The model is cast within a constitutive framework that uses Bishop's stress and suction as main variables governing the volumetric response of the material. Some enhancement to the original temperature‐independent formulation is proposed. In particular, functions describing the yield surface and the compressibility modulus are modified to account for the shrinking of the elastic domain and for the increase of irreversible volumetric strain with heating. Some examples illustrate the main features of the present proposal. Comparison with some experimental results is also included. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Gas systems in the Kuche Depression of the Tarim Basin: Source rock distributions, generation kinetics and gas accumulation history   总被引：2，自引：0，他引：2  

Wenzhi Zhao  Shuichang Zhang  Feiyu Wang  Bernhard Cramer  Jianping Chen  Yongge Sun  Baomin Zhang  Mengjun Zhao 《Organic Geochemistry》2005,36(12):1583

Six petroleum source beds have been developed in the Kuche Depression (also known as “Kuqa Depression”) of the Tarim Basin, including three lacustrine source rocks (Middle and Upper Triassic Kelamayi and Huangshanjie formations, and Middle Jurassic Qiakemake Formation) and three coal measures (Upper Triassic Taliqike Formation, Lower Jurassic Yangxia Formation, and Middle Jurassic Kezilenuer Formation). While type I–II organic matter occurs in the Middle Jurassic Qiakemake Formation (J₂q), other source beds contain dominantly type III organic matter. Gas generation rates and stable carbon isotopic kinetics of methane generation from representative source rocks collected in the Kuche Depression were measured and calculated using an on-line dry and open pyrolysis system. Combined with hydrocarbon generation history modelling, the formation and evolution processes of the Jurassic–Triassic highly efficient gas kitchens were established. High sedimentation rate in the Neogene and the fast deposition of the Kuche Formation within the Pliocene (5 Ma) in particular have led to the rapid increase in Mesozoic source rock maturity, resulting in significant dry gas generation. The extremely high gas generation rates from source kitchens have apparently expedited the formation of highly efficient gas accumulations in the Kuche Depression. Because different Mesozoic source rocks occur in different structural belts, the presence of both lacustrine and coaly gas kitchens during the Cenozoic time can be identified in the Kuche Depression. As shown by the chemical and stable carbon isotope compositions of the discovered gases, the formation of the giant gas pools in the Kela 2, Dina 2, Yaha and Wucan 1 have involved very different geological processes due to the difference in their gas source kitchens.  相似文献   

Reductive Degradation of Polychlorinated Phenols by Pd/C‐Formate: An Ecoefficient Remediation Method for Aqueous Chlorinated Phenols     

Rainer Hartung  Dieter Lenoir  Bernhard Henkelmann  Sigurd Schulte‐Hostede  Karl‐Werner Schramm 《洁净——土壤、空气、水》2007,35(3):235-238

A new catalytic dehydrohalogenation method for chlorinated phenols is described, which can be used to break down chlorinated pollutants in wastewater. It uses a system of Pd‐C as catalyst with sodium formate as reducing agent. This economic method is easy to perform with a complete degradation of the pollutant within 12 to 30 h at room temperature. The ecoefficieny of the procedure is compared with eleven alternative methods showing the special advantages of the method.  相似文献   

Seasonal Recharge and Replenishment of Sulfate Associated with Biodegradation of a Hydrocarbon Plume     

Dale R. Van Stempvoort  James Armstrong  Bernhard Mayer 《Ground Water Monitoring & Remediation》2007,27(4):110-121

  相似文献   

A Simplified, Accurate and Fast Method for Lithium Isotope Analysis of Rocks and Fluids, and δ⁷Li Values of Seawater and Rock Reference Materials     

Martin Rosner  Lary Ball  Bernhard Peucker-Ehrenbrink  Jerzy Blusztajn  Wolfgang Bach  Jörg Erzinger 《Geostandards and Geoanalytical Research》2007,31(2):77-88

We report a new approach to conduct fast and accurate lithium isotope ratio measurements by MC-ICP mass spectrometry after wet chemical sample preparation. In contrast to most previously published methods our MC-ICP-MS set-up did not use a desolvating system to achieve appropriate ion beam intensities and, therefore, was less affected by matrix-induced shifts of the instrumental mass bias. As the total lithium background and build-up in the sample introduction system was low, previous sample residues could be washed out by an extended uptake of the new sample. Elimination of a nitric acid rinse step increased the sample throughput by a factor of two and allowed the instrumental mass bias drift to be tracked more precisely. δ⁷Li values of powdered silicate rock reference materials and seawater obtained in this study revealed good accuracy and an overall analytical uncertainty of typically 0.5‰ (2s). On the basis of a comparison between our lithium isotope data and compiled literature data, we recommend preliminary average δ⁷Li values for seawater (+30.8‰) and several silicate rock reference materials (BHVO-1: +5.0‰; JA-1: +5.6‰; JB-2: +4.8‰). The compilation of published δ⁷Li values for seawater suggests that the observed large lithium isotope differences are due to inter-method and/or interlaboratory bias. Most recently published δ⁷Li values for seawater show little variation and confirm a constant lithium isotope composition (at the sub ‰ level) of seawater in well mixed ocean basins.  相似文献   

World deep-sea container shipping: by Roy Pearson and John Fossey Gower,Aldershot, UK, 1983, 288 pp     

Bernhard J. Abrahamsson 《Marine Policy》1984,8(3):287-288

  相似文献   

Studying the City Plume of Berlin on 20 July 1998 with Three Different Modelling Approaches     

Andreas Becker  Bernhard Scherer  Michael Memmesheimer  Heiner Geiß 《Journal of Atmospheric Chemistry》2002,42(1):41-70

In this paper we try to identify and describe the specifics of the Berlin city plume characterised by a zone of enhanced photochemical activity downwind of the urban area, where the major emissions of ozone precursors (NO_x and VOC) take place. Two Eulerian CTM systems (EURAD and REM3/CALGRID) and one Euler–Lagrangian model (LaMM5) are applied to thearea of Berlin/Brandenburg to investigate the processes involved in the evolution of the Berlin plume inherent to the models. The study focuses on 20 July 1998,the first special observation period (SOP) during BERLIOZ. The examination includes (1) the role of turbulence and transport and the role of mass flux to the surface during the evolution of the plume, (2) the import situation of the ground based measurement sites, (3)the terms of the ozone budget equation and their contribution to precursor distribution and ozone formation, (4) the substructures of the plume defined by its chemical regimes. Main results show that the complex meteorological conditions during this SOP with considerable turbulent transports demand an Euler–Lagrangian approach to determine the source receptor relationshipsfor the ground based measurement sites. These relations reveal that only a minor part (5%) of the air approaching Pabstthum and the more downwind (north-western) stations origins from Berlin and that the mutual transport between all sites was limited. The latter result afflicts the joint interpretation of data from different stations because the presumption to measure the same air mass is violated in many cases for this SOP. The CTM results reveal that the local net production of ozone within the plume was controlled by transport ad chemical processes both owning the same importance but tending to counteract each other. At this SOP far distance sources of ozone precursors originating from the Bohemian basin did not interfere the Berlin city plume although they generally have the potential to do so.  相似文献   

A new approach to detect the contact of two‐dimensional elliptical particles     

Algis Diugys  Bernhard Peters 《国际地质力学数值与分析法杂志》2001,25(15):1487-1500

The objective of this paper is to introduce a new algorithm to calculate analytically the overlap of two‐dimensional ellipses. The algorithm may be applied for the direct numerical simulation of granular material dynamics by the discrete element method (DEM). The stability of the algorithm is analysed. Moreover, optimization for possible iterative methods is dealt with. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Spherically symmetric cosmological perturbations in the de Donder gauge (II)     

Mark Israelit  Bernhard Rose  Heinz Dehnen 《Astrophysics and Space Science》1994,219(2):171-181

In the framework of a previously developed procedure the evolution of small spherically symmetric perturbations in a homogeneous R-W-F universe is analyzed. It turns out that the evolution tendency is mainly predicted by the state of the cosmic background. In the radiation dominated period the universe does not stimulate growing processes, a perturbation will be in a frozen state or it will diffuse. It is found that a dust dominated universe stimulates the perturbation masses to grow. The rate of this cosmic affected growing process is proportional to (R)^–1/2 (R being the scale factor). Consequently almost all galaxies were formed at the beginning of the dust dominated era.  相似文献