Thermal behavior of ferric selenite hydrates (Fe₂(SeO₃)₃·3H₂O,Fe₂(SeO₃)₃·5H₂O) and the water content in the natural ferric selenite mandarinoite     

Astrid Holzheid  Marina V. Charykova  Vladimir G. Krivovichev  Brendan Ledwig  Elena L. Fokina  Ksenia L. Poroshina  Natalia V. Platonova  Vladislav V. Gurzhiy 《Chemie der Erde / Geochemistry》2018,78(2):228-240

Any progress in our understanding of low-temperature mineral assemblages and of quantitative physico-chemical modeling of stability conditions of mineral phases, especially those containing toxic elements like selenium, strongly depends on the knowledge of structural and thermodynamic properties of coexisting mineral phases. Interrelation of crystal chemistry/structure and thermodynamic properties of selenium-containing minerals is not systematically studied so far and thus any essential generalization might be difficult, inaccurate or even impossible and erroneous. Disagreement even exists regarding the crystal chemistry of some natural and synthetic selenium-containing phases. Hence, a systematic study was performed by synthesizing ferric selenite hydrates and subsequent thermal analysis to examine the thermal stability of synthetic analogues of the natural hydrous ferric selenite mandarinoite and its dehydration and dissociation to unravel controversial issues regarding the crystal chemistry. Dehydration of synthesized analogues of mandarinoite starts at 56–87?°C and ends at 226–237?°C. The dehydration happens in two stages and two possible schemes of dehydration exist: (a) mandarinoite loses three molecules of water in the first stage of the dehydration (up to 180?°C) and the remaining two molecules of water will be lost in the second stage (>180?°C) or (b) four molecules of water will be lost in the first stage up to 180?°C and the last molecule of water will be lost at a temperature above 180?°C. Based on XRD measurements and thermal analyses we were able to deduce Fe₂(SeO₃)₃·(6-x)H₂O (x?=?0.0–1.0) as formula of the hydrous ferric selenite mandarinoite. The total amount of water apparently affects the crystallinity, and possibly the stability of crystals: the less the x value, the higher crystallinity could be expected.  相似文献   

Gradient-based Pareto optimal history matching for noisy data of multiple types     

Oleg Volkov  Vladislav Bukshtynov  Louis J. Durlofsky  Khalid Aziz 《Computational Geosciences》2018,22(6):1465-1485

The advantages of the simultaneous integration of production and time-lapse seismic data for history matching have been demonstrated in a number of previous studies. Production data provide accurate observations at particular spatial locations (wells), while seismic data enable global, though filtered/noisy, estimates of state variables. In this work, we present an efficient computational tool for bi-objective history matching, in which data misfits for both production and seismic measurements are minimized using an adjoint-gradient approach. This enables us to obtain a set of Pareto optimal solutions defining the optimal trade-off between production and seismic data misfits (which are, to some extent, conflicting). The impact of noise structure and noise level on Pareto optimal solutions is investigated in detail. We discuss the existence of the “best” trade-off solution, or least-conflicting posterior model, which corresponds to the history-matched model that is expected to provide the least-conflicting forecast of future reservoir performance. The overall framework is successfully applied in 2D and 3D compositional simulation problems to provide a single least-conflicting posterior model and, for the 2D case, multiple samples from the posterior distribution using the randomized maximum likelihood method.  相似文献   

A New Method for Low‐Temperature Decomposition of Chromites and Dichromium Trioxide using Bromic Acid Evaluated by Chromium Isotope Measurements     

Vladislav Chrastný  Jan Rohovec  Eva Čadková  Jan Pašava  Juraj Farkaš  Martin Novák 《Geostandards and Geoanalytical Research》2014,38(1):103-110

In recent years, routine application of the stable isotope determination of chromium (Cr) in environmental and health protection research has led to the search for simpler chromite decomposition techniques. As the range of Cr isotope abundance ratios in nature is very narrow, conventional chromite decomposition techniques are no longer suitable, due to the relatively high risk of contamination during laboratory procedures. We have developed a protocol for the decomposition of chromites based on oxidation by bromic acid at room temperature. The procedure takes 15 d and requires two doses of bromic acid during the reaction period (day 1 and 8), due to the limited stability of the reagent. Chromium extracted by alkaline oxidative fusion and by bromic acid decomposition yielded statistically indistinguishable δ⁵³Cr values, measured by multi‐collector inductively coupled plasma‐mass spectrometry following addition of a ⁵⁰Cr‐⁵⁴Cr double‐spike.  相似文献   

Boundaries of mantle–lithosphere domains in the Bohemian Massif as extinct exhumation channels for high-pressure rocks     

Vladislav Babuška  Jaroslava Plomerová 《Gondwana Research》2013,23(3):973-987

Five domains (microplates) have been recognized by seismic anisotropy in the mantle lithosphere of the Bohemian Massif. The mantle domains correspond to major crustal units and each of the domains bears a consistent fossil olivine fabric formed before their Variscan assembly. The present-day mantle fabric indicates that this process consisted of at least three oceanic subductions, each followed by an underthrusting of the continental lithosphere. The seismic anisotropy does not detect remnants of the oceanic subductions, but it can trace boundaries of the preserved continental domains subsequently underthrust along the paths of previous oceanic subductions. The most robust continent–continent collision was followed by westward underthrusting of the Brunovistulian mantle lithosphere, still detectable by seismic anisotropy more than 100 km beneath the Moldanubian mantle lithosphere. Major occurrences of the high-pressure/ultra high-pressure (HP–UHP) rocks follow the ENE and NNE oriented sutures and boundaries of the mantle–lithosphere domains mapped from three-dimensional modeling of body-wave anisotropy. The HP–UHP rocks are products of oceanic subductions and the following underthrusting of the continental crust and mantle lithosphere exhumed along the mantle boundaries. The close relation of the mantle sutures and occurrences of the HP–UHP rocks near the paleosubductions testifies for models interpreting the granulite–garnet peridotite association by oceanic/continental subduction/underthrusting followed by the exhumation of deep-seated rocks. Our findings support the bivergent subduction model of tectonic development of the central part of the Bohemian Massif. The inferences from seismic anisotropy image the Bohemian Massif as a mosaic of microplates with a rigid mantle lithosphere preserving a fossil olivine fabric. The collisional mantle boundaries, blurred by tectonometamorphic processes in easily deformed overlying crust, served as major exhumation channels of the HP–UHP rocks.  相似文献   

Lithogenic thallium behavior in soils with different land use     

Aleš Vaněk  Vladislav Chrastný  Martin Mihaljevič  Petr Drahota  Tomáš Grygar  Michael Komárek 《Journal of Geochemical Exploration》2009

In order to evaluate the effect of different land use on lithogenic Tl geochemistry, two forest and grassland soils developed on an identical Tl-rich substrate were examined. For this purpose a complex soil-plant investigation supplemented by mineralogical methods was performed. The modified BCR sequential extraction combined with X-ray diffraction analysis (XRD) and voltammetry of microparticles (VMP) were performed for a detailed insight on lithogenic Tl speciation and availability in both contrasting soils. It was revealed that soil forming processes like bioturbation and probably dust deposition may influence the increased input of lithogenic Tl into the forest floor. Thallium was predominantly bound within the residual fraction (up to 95%) corresponding to primary silicates (mainly orthoclase and muscovite) and probably secondary illite, which were detected by XRD in all studied horizons. Thus, stable silicates can be thought as the phases controlling the solubility of lithogenic Tl in both the forest and grassland soils. The highest portion (~ 5%) of “labile” Tl was found in the organic horizons of the forest soil indicating a distinct role of forest soil organic matter (SOM) on Tl mobilization and availability. Thallium adsorption was dominated by an identified non-crystalline Mn(III,IV) oxide detected by VMP proving thus its strong affinity for Mn oxides in mineral soils. On the contrary, Tl adsorption by more abundant Fe(III) oxides (goethite and ferrihydrite) was evaluated to be negligible. Organically bound Tl in the forest floor was found to be associated with primary SOM corresponding to the raw and partially decomposed litter of Norway spruce (Picea abies L.). Moreover, a relatively high Tl uptake was recorded by this species. In contrast, lithogenic Tl uptake by common grasses like red clover (Trifolium pratense L.) or timothy grass (Phleum pratense L.) seems to be very low.  相似文献   

Cell-vertex discretization of shallow water equations on mixed unstructured meshes     

S. Danilov  A. Androsov 《Ocean Dynamics》2015,65(1):33-47

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Calculation of energy of the barotropic-baroclinic interaction in the strait of Bab el Mandeb     

N. E. Vol’tsinger  A. A. Androsov 《Izvestiya Atmospheric and Oceanic Physics》2010,46(2):214-223

Equations for the kinetic, potential, and total energy in the curvilinear boundary-fitted coordinates are considered in the strait area and adjacent regions of the Red Sea and Gulf of Aden. The budgets of different forms of energy are presented, making it possible to assess the correctness of the formulation of the three-dimensional boundary-value problem, the accuracy of the calculation of the barotropic-baroclinic interaction in an energy norm, and the relationship between the components of energy balance. The energy fluxes in the boundary sections of the strait are estimated for the interaction of thermohaline currents with main tidal harmonics and with the total tide, as well as for the amplitude of fluctuations in boundary energy fluxes in a synodic month. The results illustrating the behavior of some dynamical characteristics and components of energy balance at vertical and horizontal sections of the strait are given.  相似文献   

On the circular Sitnikov problem: the alternation of stability and instability in the family of vertical motions     

Vladislav V. Sidorenko 《Celestial Mechanics and Dynamical Astronomy》2011,109(4):367-384

This paper is devoted to the special case of the restricted circular three-body problem, when the two primaries are of equal mass, while the third body of negligible mass performs oscillations along a straight line perpendicular to the plane of the primaries (so called periodic vertical motions). The main goal of the paper is to study the stability of these periodic motions in the linear approximation. A special attention is given to the alternation of stability and instability within the family of periodic vertical motions, whenever their amplitude is varied in a continuous monotone manner.  相似文献   

Surface Miners: Evaluation of the Production Rate and Cutting Performance Based on Rock Properties and Specific Energy     

Chiara Origliasso  Marilena Cardu  Vladislav Kecojevic 《Rock Mechanics and Rock Engineering》2014,47(2):757-770

The purpose of this research was to evaluate the production rate (PR) and cutting performance of surface miners (SM) based on rock properties and specific energy (SE). We use data from equipment manufacturers and experimental data in this study and propose a new method and equations to determine both the PR and the cutting speed of SM. The unconfined compressive strength (UCS) of the rock, its abrasivity, and the machine’s engine power are the three most important factors influencing the PR. Moreover, the cutting depth, UCS, and engine power have a significant impact on the cutting speed. We propose a new method and equations to determine the energy required to cut a volume unit and a surface unit, i.e., specific energy, and establish the relationship between SE, UCS, and PR. The results of this study can be used by surface miner operators to evaluate the applicability of the machines to a specific mine site.  相似文献   

Distribution of thallium and accompanying metals in tree rings of Scots pine (Pinus sylvestris L.) from a smelter-affected area     

Aleš Vaněk  Vladislav Chrastný  Leslaw Teper  Jerzy Cabala  Vít Penížek  Michael Komárek 《Journal of Geochemical Exploration》2011

Distribution of Tl, Zn, Cd, Pb, K, Ca, Mg and Mn and Pb isotopic composition in tree rings of Scots pine (Pinus sylvestris L.) from an area affected by primary Zn smelting (Olkusz, southern Poland) were investigated. Elevated concentrations of Tl (up to 0.8 mg kg⁻¹) in pine trees imply that conifers tend to accumulate this metal to some extent. A generally positive relationship between soil and tree-ring Tl levels was identified. The Tl patterns in stem wood did not correspond to changes in Tl deposition; the lateral translocation of Tl in the sapwood and its accumulation at the sapwood-heartwood boundary (i.e., in the inner sapwood) is suggested. It is probable that the specific behavior of Tl in trees results from its biogeochemical analogy with K. In contrast, tree-ring patterns of Zn and Cd significantly correlated with their deposition; nevertheless, a partial shift of these metals towards the stem center cannot be excluded. The isotopic composition of Pb (²⁰⁶Pb/²⁰⁷Pb ~ 1.172–1.184) in trees and underlying soils revealed the predominant influence of smelter emissions (²⁰⁶Pb/²⁰⁷Pb ~ 1.17) on Pb contamination. Analysis of main nutrients (Ca, Mg and Mn) in wood reflected environmental changes related to acid deposition.  相似文献