Reversible control of aqueous aluminum and silica during the irreversible evolution of natural waters     

Tomáš Pačes 《Geochimica et cosmochimica acta》1978,42(10):1487-1493

Primary aluminosilicates are transformed at low temperature into a sequence of metastable and thermodynamically stable secondary minerals by an irreversible process. The aqueous concentrations in the associated solution may continuously change during the process or they may be maintained constant through hydrodynamic or chemical steady-state mechanisms or through chemical equilibrium with a reversible metastable solid.Disequilibrium indices calculated for 152 natural waters and experimental solutions show that the solutions are unsaturated with amorphous aluminum hydroxide, microcrystalline gibbsite, amorphous silica and amorphous aluminosilicate, and they are supersaturated with gibbsite and kaolinite. The disequilibrium index for halloysite varies widely from unsaturation to supersaturation.Only the index for the reversible metastable cryptocrystalline aluminosilicate whose composition is pH dependent is very close to zero indicating saturation. The index varies in a narrow range. This, supported by electron micrographs and the results of X-ray fluorescence spectroscopy presented by other authors, suggests that this metastable solid, and not the secondary aluminosilicate minerals, controls the concentrations of alumina and silica in natural waters.  相似文献   

Hydrogeological and isotope mapping of the karstic River Savica in NW Slovenia     

Mihael Brenčič  Polona Vreča 《Environmental Earth Sciences》2016,75(8):651

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The response of mercury (Hg) transformation in soil to sulfur compounds and sulfur-rich biowaste application     

Jiřina Száková  Andrea Burešová  Lukáš Praus  Mercedes García-Sánchez  Zlata Holečková  Jiří Gabriel  Jiřina Sysalová  Rostislav Červenka  Josef Komárek  Slávka Grohová  Pavel Tlustoš 《Environmental Earth Sciences》2016,75(7):584

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Regional-scale screening of groundwater pollution risk induced by historical mining activities in Serbia     

Nebojša Atanacković  Veselin Dragišić  Vladimir Živanović  Sunčica Gardijan  Sava Magazinović 《Environmental Earth Sciences》2016,75(16):1152

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Weather and traffic accidents in the Czech Republic, 1979–2020     

Brázdil  Rudolf  Chromá  Kateřina  Zahradníček  Pavel  Dobrovolný  Petr  Dolák  Lukáš 《Theoretical and Applied Climatology》2022,149(1-2):153-167

Theoretical and Applied Climatology - Police records, kept in the form of yearbooks, enabled analysis of the possible relationships between traffic accidents and the weather in the Czech Republic...  相似文献   

Application of run-off model as a contribution to the torrential flood risk management in Topčiderska Reka watershed,Serbia     

Ana M. Petrović  Jelena Kovačević-Majkić  Marko V. Milošević 《Natural Hazards》2016,82(3):1743-1753

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Fluid-driven destabilization of REE-bearing accessory minerals in the granitic orthogneisses of North Veporic basement (Western Carpathians,Slovakia)     

M. Ondrejka  M. Putiš  P. Uher  I. Schmiedt  L. Pukančík  P. Konečný 《Mineralogy and Petrology》2016,110(5):561-580

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Inversion of travel times obtained during active seismic refraction experiments CELEBRATION 2000, ALP 2002 and SUDETES 2003     

B. Růžek  P. Hrubcová  M. Novotný  A. Špičák  O. Karousová 《Studia Geophysica et Geodaetica》2007,51(1):141-164

A series of kinematic inversions based on robust non-linear optimization approach were performed using travel time data from a series of seismic refraction experiments: CELEBRATION 2000, ALP 2002 and SUDETES 2003. These experiments were performed in Central Europe from 2000 to 2003. Data from 8 profiles (CEL09, CEL10, Alp01, S01, S02, S03, S04 and S05) were processed in this study. The goal of this work was to find seismic velocity models yielding travel times consistent with observed data. Optimum 2D inhomogeneous isotropic P-wave velocity models were computed. We have developed and used a specialized two-step inverse procedure. In the first “parametric” step, the velocity model contains interfaces whose shapes are defined by a number of parameters. The velocity along each interface is supposed to be constant but may be different along the upper and lower side of the interface. Linear vertical interpolation is used for points in between interfaces. All parameters are searched for using robust non-linear optimization (Differential Evolution algorithm). Rays are continuously traced by the bending technique. In the second “tomographic” step, small-scale velocity perturbations are introduced in a dense grid covering the currently obtained velocity model. Rays are fixed in this step. Final velocity models yield travel time residuals comparable to typical picking errors (RMS ∼ 0.1 s). As a result, depth-velocity cross-sections of P waves along all processed profiles are obtained. The depth range of the models is 35–50 km, the velocity varies in the range 3.5–8.2 km/s. Lowest velocities are detected in near-surface depth sections crossing sedimentary formations. The middle crust is generally more homogeneous and has typical P wave velocity around 6 km/s. Surprisingly the lower crust is less homogeneous and the computed velocity is in the range 6.5–7.5 km/s. The MOHO is detected in the depth ≈30–45 km.  相似文献   

Comparison of true-height electron density profiles derived by POLAN and NHPC methods     

P. Šauli  Z. Mošna  J. Boška  D. Kouba  J. Laštovička  D. Altadill 《Studia Geophysica et Geodaetica》2007,51(3):449-459

The changing state of the ionosphere is generally monitored by networks of vertical ionosondes that provide us with regular ionospheric sounding. Many ionospheric applications require determination of the true-height electron density profiles. Therefore, ionograms must be further inverted into real-height electron density profiles. The paper presents the comparison study of the true-height electron density profiles inverted from ionograms using two different methods POLAN (Titheridge, 1985) and NHPC (Huang and Reinish, 1996; Reinish et al., 2005), widely used by the ionospheric research community. Our results show significant systematic differences between electron density profiles calculated by these two inversion methods. pkn@ufa.cas.cz  相似文献   

Metal speciation and attenuation in stream waters and sediments contaminated by landfill leachate     

Vojtěch Ettler  Marek Matura  Martin Mihaljevič  Petr Bezdička 《Environmental Geology》2006,49(4):610-619

The degree of metal contamination (Zn, Pb, Cu, Ni, Cd) has been investigated in the vicinity of an old unmonitored municipal landfill in Prague, Czech Republic, where the leachate is directly drained into a surface stream. The water chemistry was coupled with investigation of the stream sediment (aqua regia extract, sequential extraction, voltammetry of microparticles) and newly formed products (SEM/EDS, XRD). The MINTEQA2 speciation-solubility calculation showed that the metals (Zn, Pb, Cu, Ni) are mainly present as carbonate complexes in leachate-polluted surface waters. These waters were oversaturated with respect to Fe(III) oxyhydroxides, calcite (CaCO₃) and other carbonate phases. Three metal attenuation mechanisms were identified in leachate-polluted surface waters: (i) spontaneous precipitation of metal-bearing calcite exhibiting significant concentrations of trace elements (Fe, Mn, Mg, Sr, Ba, Pb, Zn, Ni); (ii) binding to Fe(III) oxyhydroxides (mainly goethite, FeOOH) (Pb, Zn, Cu, Ni); and (iii) preferential bonding to sediment organic matter (Cu). These processes act as the key scavenging mechanisms and significantly decrease the metal concentrations in leachate-polluted water within 200 m from the direct leachate outflow into the stream. Under the near-neutral conditions governing the sediment/water interface in the landfill environment, metals are strongly bound in the stream sediment and remain relatively immobile.  相似文献