The IWAS-ToolBox: Software coupling for an integrated water resources management   总被引：4，自引：4，他引：0  

Thomas Kalbacher  Jens-Olaf Delfs  Haibing Shao  Wenqing Wang  Marc Walther  Luis Samaniego  Christoph Schneider  Rohini Kumar  Andreas Musolff  Florian Centler  Feng Sun  Anke Hildebrandt  Rudolf Liedl  Dietrich Borchardt  Peter Krebs  Olaf Kolditz 《Environmental Earth Sciences》2012,65(5):1367-1380

Numerical modeling of interacting flow and transport processes between different hydrological compartments, such as the atmosphere/land surface/vegetation/soil/groundwater systems, is essential for understanding the comprehensive processes, especially if quantity and quality of water resources are in acute danger, like e.g. in semi-arid areas and regions with environmental contaminations. The computational models used for system and scenario analysis in the framework of an integrated water resources management are rapidly developing instruments. In particular, advances in computational mathematics have revolutionized the variety and the nature of the problems that can be addressed by environmental scientists and engineers. It is certainly true that for each hydro-compartment, there exists many excellent simulation codes, but traditionally their development has been isolated within the different disciplines. A new generation of coupled tools based on the profound scientific background is needed for integrated modeling of hydrosystems. The objective of the IWAS-ToolBox is to develop innovative methods to combine and extend existing modeling software to address coupled processes in the hydrosphere, especially for the analysis of hydrological systems in sensitive regions. This involves, e.g. the provision of models for the prediction of water availability, water quality and/or the ecological situation under changing natural and socio-economic boundary conditions such as climate change, land use or population growth in the future.  相似文献   

Suitability of Existing Numerical Model Codes and Thermodynamic Databases for the Prognosis of Calcite Dissolution Processes in Near-Surface Sediments Due to a CO2 Leakage Investigated by Column Experiments     

Christoph Haase  Andreas Dahmke  Markus Ebert  Dirk Schäfer  Frank Dethlefsen 《Aquatic Geochemistry》2014,20(6):639-661

Among the risks of CO₂ storage is the potential of CO₂ leakage into overlaying formations and near-surface potable aquifers. Through a leakage, the CO₂ can intrude into protected groundwater resources, which can lead to groundwater acidification followed by potential mobilisation of heavy metals and other trace metals through mineral dissolution or ion exchange processes. The prediction of pH buffer reactions in the formations overlaying a CO₂ storage site is essential for assessing the impact of CO₂ leakages in terms of trace metal mobilisation. For buffering the pH-value, calcite dissolution is one of the most important mechanisms. Although calcite dissolution has been studied for decades, experiments conducted under elevated CO₂ partial pressures are rare. Here, the first study for column experiments is presented applying CO₂ partial pressures from 6 to 43 bars and realising a near-natural flow regime. Geochemical calculations of calcite dissolution kinetics were conducted using PHREEQC together with different thermodynamic databases. Applying calcite surface areas, which were previously acquired by N₂-BET or calculated based on grain diameters, respectively, to the rate laws according to Plummer et al. (Am J Sci 278:179–216, doi:10.2475/ajs.278.2.179, 1978) or Palandri and Kharaka (US Geol Surv Open file Rep 2004–1068:71, 2004) in the numerical simulations led to an overestimation of the calcite dissolution rate by up to three orders of magnitude compared to the results of the column experiments. Only reduction of the calcite surface area in the simulations as a fitting procedure allowed reproducing the experimental results. A reason may be that the diffusion boundary layer (DBL), which depends on the groundwater flow velocity and develops at the calcite grain surface separating it from the bulk of the solution, has to be regarded: The DBL leads to a decrease in the calcite dissolution rate under natural laminar flow conditions compared to turbulent mixing in traditional batch experiments. However, varying the rate constants by three orders of magnitudes in a field scale PHREEQC model simulating a CO₂ leakage produced minor variations in the pH buffering through calcite dissolution. This justifies the use of equilibrium models when calculating the calcite dissolution in CO₂ leakage scenarios for porous aquifers and slow or moderate groundwater flow velocities. However, the selection of the thermodynamic database has an impact on the dissolved calcium concentration, leading to an uncertainty in the simulation results. The resulting uncertainty, which applies also to the calculated propagation of an aquifer zone depleted in calcite through dissolution, seems negligible for shallow aquifers of approximately 60 m depth, but amounts to 35 % of the calcium concentration for aquifers at a depth of approximately 400 m.  相似文献   

Generalized integer aperture estimation for partial GNSS ambiguity fixing     

Andreas Brack  Christoph Günther 《Journal of Geodesy》2014,88(5):479-490

In satellite navigation, the key to high precision is to make use of the carrier-phase measurements. The periodicity of the carrier-phase, however, leads to integer ambiguities. Often, resolving the full set of ambiguities cannot be accomplished for a given reliability constraint. In that case, it can be useful to resolve a subset of ambiguities. The selection of the subset should be based not only on the stochastic system model but also on the actual measurements from the tracking loops. This paper presents a solution to the problem of joint subset selection and ambiguity resolution. The proposed method can be interpreted as a generalized version of the class of integer aperture estimators. Two specific realizations of this new class of estimators are presented, based on different acceptance tests. Their computation requires only a single tree search, and can be efficiently implemented, e.g., in the framework of the well-known LAMBDA method. Numerical simulations with double difference measurements based on Galileo E1 signals are used to evaluate the performance of the introduced estimation schemes under a given reliability constraint. The results show a clear gain of partial fixing in terms of the probability of correct ambiguity resolution, leading to improved baseline estimates.  相似文献   

Web-based 4D visualization of marine geo-data using WebGL     

Bernd Resch  Ralf Wohlfahrt  Christoph Wosniok 《制图学和地理信息科学》2014,41(3):235-247

For marine logistics and maintenance of extensive and expensive marine engineering projects in the coastal zone, it is essential that institutions provide the public with relevant information in an easily understandable yet comprehensive manner over the web. A perennial challenge, however, has been the development of spatio-temporal (four-dimensional (4D)) geo-visualization algorithms to enable the integration of time-varying geo-information in map-based visualizations on the Internet. In this paper, we address the challenge of visualizing marine spatial data in web-based applications through a 4D visualization concept, focusing on usability criteria, performance parameters, the required implementation effort, and delivering a breath of spatial information that supports decision-making on multiple levels. We used Web Graphic Library (WebGL) to validate our concept through a prototypical implementation. In our technology evaluation, WebGL proved highly suitable for the development of interactive, responsive, efficient, and mobile web-based Geographic Information applications, including 2D, 3D, and 4D (spatiotemporal) content. During our research, we identified a number of open research questions, including mapping graphic variables to thematic expressivity, representation of the time dimension in 4D systems, generic temporal generalization, and integration of (pseudo-)photorealistic illustrations in web-based geo-visualization systems.  相似文献   

A High Order Perturbation Analysis of the Sitnikov Problem     

Johannes Hagel  Christoph Lhotka 《Celestial Mechanics and Dynamical Astronomy》2005,93(1-4):201-228

The Sitnikov problem is one of the most simple cases of the elliptic restricted three body system. A massless body oscillates along a line (z) perpendicular to a plane (x,y) in which two equally massive bodies, called primary masses, perform Keplerian orbits around their common barycentre with a given eccentricity e. The crossing point of the line of motion of the third mass with the plane is equal to the centre of gravity of the entire system. In spite of its simple geometrical structure, the system is nonlinear and explicitly time dependent. It is globally non integrable and therefore represents an interesting application for advanced perturbative methods. In the present work a high order perturbation approach to the problem was performed, by using symbolic algorithms written in Mathematica. Floquet theory was used to derive solutions of the linearized equation up to 17th order in e. In this way precise analytical expressions for the stability of the system were obtained. Then, applying the Courant and Snyder transformation to the nonlinear equation, algebraic solutions of seventh order in z and e were derived using the method of Poincaré–Lindstedt. The enormous amount of necessary computations were performed by extensive use of symbolic programming. We developed automated and highly modularized algorithms in order to master the problem of ordering an increasing number of algebraic terms originating from high order perturbation theory.  相似文献   

High order normal form construction near the elliptic orbit of the Sitnikov problem     

Sara Di Ruzza  Christoph Lhotka 《Celestial Mechanics and Dynamical Astronomy》2011,111(4):449-464

We consider the Sitnikov problem; from the equations of motion we derive the approximate Hamiltonian flow. Then, we introduce suitable action–angle variables in order to construct a high order normal form of the Hamiltonian. We introduce Birkhoff Cartesian coordinates near the elliptic orbit and we analyze the behavior of the remainder of the normal form. Finally, we derive a kind of local stability estimate in the vicinity of the periodic orbit for exponentially long times using the normal form up to 40th order in Cartesian coordinates.  相似文献   

Cosmogenic isotope (Cl) surface exposure dating of the Norber erratics, Yorkshire Dales: Further constraints on the timing of the LGM deglaciation in Britain     

Peter J. Vincent  Peter Wilson  Tom C. Lord  Christoph Schnabel 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(1):24-31

Cosmogenic isotope (³⁶Cl) surface exposure dating of four of the erratic boulders at Norber in the Yorkshire Dales National Park, northwest England, yielded mean ages of ∼22.2 ± 2.0 ka BP and ∼18.0 ± 1.6 ka BP for their emplacement. These two mean values derive from different ³⁶Cl production rates used for exposure age calculation. The ages are uncorrected for temporal variations in production rates and may underestimate the true ages by 5-7%. The former age, although implying early deglaciation for this area of the British ice sheet, is not incompatible with minimum deglaciation ages from other contexts and locations in northwest England. However, the latter age is more consistent with the same minimum deglaciation ages and geochronological evidence for ice-free conditions in parts of the northern sector of the Irish Sea. Within uncertainties, the younger of the mean ages from Norber may indicate that boulder emplacement was associated with North Atlantic Heinrich event 1. The limited spatial (downvalley) extent of the Norber boulders implies that at the time of their deposition the ice margin was coincident with the distal margin of the erratic train. Loss of ice cover at Norber was followed by persistent stadial conditions until the abrupt opening of the Lateglacial Interstadial when large carnivorous mammals colonised the area. The ³⁶Cl ages are between ∼3.0 ka and ∼13.0 ka older than previous estimates based on rates of limestone dissolution derived from the heights of pedestals beneath the erratics.  相似文献   

The biogeochemistry of sorbed methane in marine sediments     

Tobias F. Ertefai  Verena B. Heuer  Christoph Vogt  Jeffrey Seewald 《Geochimica et cosmochimica acta》2010,74(21):6033-6048

Sorption of volatile hydrocarbon gases (VHCs) to marine sediments is a recognized phenomenon that has been investigated in the context of petroleum exploration. However, little is known about the biogeochemistry of sorbed methane and higher VHCs in environments that are not influenced by thermogenic processes. This study evaluated two different extraction protocols for sorbed VHCs, used high pressure equipment to investigate the sorption of methane to pure clay mineral phases, and conducted a geochemical and mineralogical survey of sediment samples from different oceanographic settings and geochemical regimes that are not significantly influenced by thermogenic gas. Extraction of sediments under alkaline conditions yielded higher concentrations of sorbed methane than the established protocol for acidic extraction. Application of alkaline extraction in the environmental survey revealed the presence of substantial amounts of sorbed methane in 374 out of 411 samples (91%). Particularly high amounts, up to 2.1 mmol kg⁻¹ dry sediment, were recovered from methanogenic sediments. Carbon isotopic compositions of sorbed methane suggested substantial contributions from biogenic sources, both in sulfate-depleted and sulfate-reducing sediments. Carbon isotopic relationships between sorbed and dissolved methane indicate a coupling of the two pools. While our sorption experiments and extraction conditions point to an important role for clay minerals as sorbents, mineralogical analyses of marine sediments suggest that variations in mineral composition are not controlling variations in quantities of sorbed methane. We conclude that the distribution of sorbed methane in sediments is strongly influenced by in situ production.  相似文献   

Age constraints on faulting and fault reactivation: a multi-chronological approach   总被引：2，自引：0，他引：2  

Wolfgang Siebel  Horst P. Hann  Martin Danišík  Cosmas K. Shang  Christoph Berthold  Johann Rohrmüller  Klaus Wemmer  Noreen J. Evans 《International Journal of Earth Sciences》2010,99(6):1187-1197

Movement within the Earth’s upper crust is commonly accommodated by faults or shear zones, ranging in scale from micro-displacements to regional tectonic lineaments. Since faults are active on different time scales and can be repeatedly reactivated, their displacement chronology is difficult to reconstruct. This study represents a multi-geochronological approach to unravel the evolution of an intracontinental fault zone locality along the Danube Fault, central Europe. At the investigated fault locality, ancient motion has produced a cataclastic deformation zone in which the cataclastic material was subjected to hydrothermal alteration and K-feldspar was almost completely replaced by illite and other phyllosilicates. Five different geochronological techniques (zircon Pb-evaporation, K–Ar and Rb–Sr illite, apatite fission track and fluorite (U-Th)/He) have been applied to explore the temporal fault activity. The upper time limit for initiation of faulting is constrained by the crystallization age of the primary rock type (known as “Kristallgranit”) at 325 ± 7 Ma, whereas the K–Ar and Rb–Sr ages of two illite fractions <2 μm (266–255 Ma) are interpreted to date fluid infiltration events during the final stage of the cataclastic deformation period. During this time, the “Kristallgranit” was already at or near the Earth’s surface as indicated by the sedimentary record and thermal modelling results of apatite fission track data. (U–Th)/He thermochronology of two single fluorite grains from a fluorite–quartz vein within the fault zone yield Cretaceous ages that clearly postdate their Late-Variscan mineralization age. We propose that later reactivation of the fault caused loss of helium in the fluorites. This assertion is supported by geological evidence, i.e. offsets of Jurassic and Cretaceous sediments along the fault and apatite fission track thermal modelling results are consistent with the prevalence of elevated temperatures (50–80°C) in the fault zone during the Cretaceous.  相似文献   

Detecting thermal anomalies within the Molasse Basin, southern Germany     

Wolfram Rühaak  Volker Rath  Christoph Clauser 《Hydrogeology Journal》2010,18(8):1897-1915

The groundwater flow regime at great depth within the Molasse Basin (SW Germany) was studied. Data relevant for a flow model at 600–1,600 m depth are sparse in the western part of the basin. However, temperature measurements are available covering much of the area at a wide range of depths. Therefore, a thermal 3D steady-state model was set up with the aim of comparing modeled with observed subsurface temperatures. Stratigraphic information from many boreholes was also available, but only a few values of rock thermal conductivity and heat-production rate could be obtained. Some strong thermal residual anomalies were identified with respect to the purely conductive model, especially along fault zones, and within stratigraphic layers with high hydraulic conductivity. These anomalies can be explained by various advective heat-transport mechanisms, yet most explanations can be eliminated. The most plausible constellation explaining the major positive thermal anomalies of 10 Kelvin and more is a fault zone of E–W strike, intersected by an aquifer with flow parallel to the fault zone. This concept was investigated by using a simplified type model. In spite of some shortcomings, the method presented here can be used to identify temperature anomalies, and to identify possible explanations.  相似文献