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1.
Haibing Shao Svitlana V. Dmytrieva Olaf Kolditz Dmitrii A. Kulik Wilfried Pfingsten Georg Kosakowski 《Applied Geochemistry》2009
The numerical simulation of reactive mass transport processes in complex geochemical environments is an important tool for the performance assessment of future waste repositories. A new combination of the multi-component mass transport code GeoSys/RockFlow and the Gibbs Energy Minimization (GEM) equilibrium solver GEM-Selektor is used to calculate the accurate equilibrium of multiple non-ideal solid solutions which are important for the immobilization of radionuclides such as Ra. The coupled code is verified by a widely used benchmark of dissolution–precipitation in a calcite–dolomite system. A more complex application shown in this paper is the transport of Ra in the near-field of a nuclear waste repository. Depending on the initial inventories of Sr, Ba and sulfate, non-ideal sulfate and carbonate solid solutions can fix mobile Ra cations. Due to the complex geochemical interactions, the reactive transport simulations can describe the migration of Ra in a much more realistic way than using the traditional linear KD approach only. 相似文献
2.
Frank Beyrich Jens-Peter Leps Matthias Mauder Jens Bange Thomas Foken Sven Huneke Horst Lohse Andreas Lüdi Wouter M. L. Meijninger Dmitrii Mironov Ulrich Weisensee Peter Zittel 《Boundary-Layer Meteorology》2006,121(1):33-65
Micrometeorological measurements (including eddy-covariance measurements of the surface fluxes of sensible and latent heat) were performed during the LITFASS-2003 experiment at 13 field sites over different types of land use (forest, lake, grassland, various agricultural crops) in a 20 × 20 km2 area around the Meteorological Observatory Lindenberg (MOL) of the German Meteorological Service (Deutscher Wetterdienst, DWD). Significant differences in the energy fluxes could be found between the major land surface types (forest, farmland, water), but also between the different agricultural crops (cereals, rape, maize). Flux ratios between the different surfaces changed during the course of the experiment as a result of increased water temperature of the lake, changing soil moisture, and of the vegetation development at the farmland sites. The measurements over grass performed at the boundary-layer field site Falkenberg of the MOL were shown to be quite representative for the farmland part of the area. Measurements from the 13 sites were composed into a time series of the area-averaged surface flux by taking into account the data quality of the single flux values from the different sites and the relative occurrence of each surface type in the area. Such composite fluxes could be determined for about 80% of the whole measurement time during the LITFASS-2003 experiment. Comparison of these aggregated surface fluxes with area-averaged fluxes from long-range scintillometer measurements and from airborne measurements showed good agreement. 相似文献
3.
A multi-limit formulation for the equilibrium depth of a stably stratified boundary layer 总被引：1，自引：0，他引：1
Currently no expression for the equilibrium depth of the turbulent stably-stratified boundary layer is available that accounts
for the combined effects of rotation, surface buoyancy flux and static stability in the free flow. Various expressions proposed
to date are reviewed in the light of what is meant by the stable boundary layer. Two major definitions are thoroughly discussed.
The first emphasises turbulence and specifies the boundary layer as a continuously and vigorously turbulent layer adjacent
to the surface. The second specifies the boundary layer in terms of the mean velocity profile, e.g. by the proximity of the
actual velocity to the geostrophic velocity. It is shown that the expressions based on the second definition are relevant
to the Ekman layer and portray the depth of the turbulence in the intermediate regimes, when the effects of static stability
and rotation essentially interfere. Limiting asymptotic regimes dominated by either stratification or rotation are examined
using the energy considerations. As a result, a simple equation for the depth of the equilibrium stable boundary layer is
developed. It is valid throughout the range of stability conditions and remains in force in the limits of a perfectly neutral
layer subjected to rotation and a rotation-free boundary layer dominated by surface buoyancy flux or stable density stratification
at its outer edge. Dimensionless coefficients are estimated using data from observations and large-eddy simulations. Well-known
and widely used formulae proposed earlier by Zilitinkevich and by Pollard, Rhines and Thompson are shown to be characteristic
of the above interference regimes, when the effects of rotation and static stability (due to either surface buoyancy flux,
or stratification at the outer edge of the boundary layer) are roughly equally important. 相似文献
4.
The natural early-diagenetic environment ``anoxicporewater – authigenic mineral phases' has beencharacterized in sediment of the Gotland Deep,Baltic Sea, by a closed-system model. Occurrence ofcarbonate precipitates as thin almost pure whitelaminae was considered as a natural experiment forlong-term equilibration between these phases andporewater. Plots of distribution coefficientsindicate that metastable equilibrium exists betweenporewater and the authigenic Ca-rich rhodochrositephases below 7 cm depth. A thermodynamic model ofporewater geochemistry at in situ P = 25 barand T = 5 °C was developed using the Gibbsenergy minimization (GEM) approach. The values of isobaric-isothermal potentials of Mn, Ca, Fe, Mg,Sr, Ba, C, and O, calculated from the porewatercomposition, were used in a new ``dual thermodynamic'calculation approach to estimate solid activitycoefficients of the end-members in the non-idealsolid solution (Mn, Ca, Mg, Sr, Ba, Fe)CO3,i.e., at full major and minor multi-componentcomplexity. The regular Margules interactionparameters for the composing binaries estimated bythis model were Mn-Ca = 1.9 ± 0.5,Mn-Mg = 0.6,Ca-Mg = 3.7,Mn-Fe = 0.2,Ca-Fe = 2.8,Mn-Sr = 9.7,Ca-Sr = 2.15,Mn-Ba = 4.0,Ca-Ba = 1.4,validating the theoretical predictions given byLippmann in his pioneering 1980's paper. Thestrictly thermodynamic equilibrium model is not onlyable to match both the measured porewater andcarbonate solid-solution composition, but also topredict that the porewater pH, pe, alkalinity, anddissolved Mn, Fe, and S concentrations arecontrolled by the authigenic mineral bufferingassemblage mackinawite-greigite-rhodochrosite. Ourmodel is only compatible with the idea of ACRformation with typical composition (XMnbetween 70–75%) in the topmost sediment layerwhich, however, needs a major source ofMnaq
II. This is provided by reduction ofparticulate Mn oxides precipitated in significantamounts in the water column upon major inflow eventsin the Baltic Sea. The model enables also to set upscenarios of changing environmental conditions, e.g.,to predict the non-linear response of the carbonatesolid-solution composition to changes in Mn loading,alkalinity and salinity of the sediment-watersystem. The results suggest that the major andespecially minor element contents (Sr, Mg, Ba) inauthigenic carbonates can be applied as anenvironmental paleoproxy. 相似文献
5.
Boundary-Layer Meteorology - 相似文献
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7.
DmitriiV.Sevastyanov NadezhdaI.Dorofeyk 《山地科学学报》2005,2(1):86-90
Mongolia-extensive inside-continental country,with an area of more than 1,5oo,ooo km^2. There are some mountain areas - Hangai and Hantai in the North, and Mongolian Altai in the West, and Gobi Altai - in the Center of the country. 相似文献
8.
Experimental shock metamorphism of terrestrial basalts: Agglutinate-like particle formation,petrology, and magnetism 
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下载免费PDF全文 Dmitrii D. Badyukov Natalia S. Bezaeva Pierre Rochette Jérôme Gattacceca Joshua M. Feinberg Myriam Kars Ramon Egli Jouko Raitala Dilyara M. Kuzina 《Meteoritics & planetary science》2018,53(1):131-150
Hypervelocity impacts occur on bodies throughout our solar system, and play an important role in altering the mineralogy, texture, and magnetic properties in target rocks at nanometer to planetary scales. Here we present the results of hypervelocity impact experiments conducted using a two-stage light-gas gun with 5 mm spherical copper projectiles accelerated toward basalt targets with ~6 km s−1 impact velocities. Four different types of magnetite- and titanomagnetite-bearing basalts were used as targets for seven independent experiments. These laboratory impacts resulted in the formation of agglutinate-like particles similar in texture to lunar agglutinates, which are an important fraction of lunar soil. Materials recovered from the impacts were examined using a suite of complementary techniques, including optical and scanning electron microscopy, micro-Raman spectroscopy, and high- and low-temperature magnetometry, to investigate the texture, chemistry, and magnetic properties of newly formed agglutinate-like particles and were compared to unshocked basaltic parent materials. The use of Cu-projectiles, rather than Fe- and Ni-projectiles, avoids magnetic contamination in the final shock products and enables a clearer view of the magnetic properties of impact-generated agglutinates. Agglutinate-like particles show shock features, such as melting and planar deformation features, and demonstrate shock-induced magnetic hardening (two- to seven-fold increases in the coercivity of remanence Bcr compared to the initial target materials) and decreases in low-field magnetic susceptibility and saturation magnetization. 相似文献
9.
Ferdinand F. Hingerl Georg Kosakowski Thomas Wagner Dmitrii A. Kulik Thomas Driesner 《Computational Geosciences》2014,18(2):227-242
GEMSFIT, a parallelized open-source tool for fitting thermodynamic activity models has been developed. It is the first open-source implementation of a generic geochemical-thermodynamic fitting tool coupled to a chemical equilibrium solver which uses the direct Gibbs energy minimization (GEM) approach. This enables speciation-based fitting of complex solution systems such as solid solutions and mixed solvents. The extendable framework of GEMSFIT provides a generic interface for fitting geochemical activity models at varying system compositions, temperatures and pressures. GEMSFIT provides the most common tools for statistical analysis which allow thorough evaluation of the fitted parameters. The program can receive input of measured data from a PostgreSQL database server or exported spreadsheets. The fitting tool allows for bound, linear, and nonlinear (in)equality-constrained minimization of weighted squared residuals of highly nonlinear systems over a wide temperature and pressure interval only limited by user-supplied thermodynamic data. Results from parameter regression as well as from statistical analysis can be visualized and directly printed to various graphical formats. Efficient use of the code is facilitated by a graphical user interface which assists in setting up GEMSFIT input files. The usage and resulting output of GEMSFIT is demonstrated by results from parameter regression of the extended universal quasichemical aqueous activity model for geothermal brines. 相似文献
10.
Dmitrii A. Kulik Thomas Wagner Svitlana V. Dmytrieva Georg Kosakowski Ferdinand F. Hingerl Konstantin V. Chudnenko Urs R. Berner 《Computational Geosciences》2013,17(1):1-24
Reactive mass transport (RMT) simulation is a powerful numerical tool to advance our understanding of complex geochemical processes and their feedbacks in relevant subsurface systems. Thermodynamic equilibrium defines the baseline for solubility, chemical kinetics, and RMT in general. Efficient RMT simulations can be based on the operator-splitting approach, where the solver of chemical equilibria is called by the mass transport part for each control volume whose composition, temperature, or pressure has changed. Modeling of complex natural systems requires consideration of multiphase–multicomponent geochemical models that include nonideal solutions (aqueous electrolytes, fluids, gases, solid solutions, and melts). Direct Gibbs energy minimization (GEM) methods have numerous advantages for the realistic geochemical modeling of such fluid–rock systems. Substantial improvements and extensions to the revised GEM interior point method algorithm based on Karpov’s convex programming approach are described, as implemented in the GEMS3K C/C+?+ code, which is also the numerical kernel of GEM-Selektor v.3 package (http://gems.web.psi.ch). GEMS3K is presented in the context of the essential criteria of chemical plausibility, robustness of results, mass balance accuracy, numerical stability, speed, and portability to high-performance computing systems. The stand-alone GEMS3K code can treat very complex chemical systems with many nonideal solution phases accurately. It is fast, delivering chemically plausible and accurate results with the same or better mass balance precision as that of conventional speciation codes. GEMS3K is already used in several coupled RMT codes (e.g., OpenGeoSys-GEMS) capable of high-performance computing. 相似文献