An experimental study of Cobalt (II) complexation in Cl and H₂S-bearing hydrothermal solutions     

Art.A. Migdisov  D. Zezin  A.E. Williams-Jones 《Geochimica et cosmochimica acta》2011,75(14):4065-5495

The speciation of cobalt (II) in Cl⁻ and H₂S-bearing solutions was investigated spectrophotometrically at temperatures of 200, 250, and 300 °C and a pressure of 100 bars, and by measuring the solubility of cobaltpentlandite at temperatures of 120-300 °C and variable pressures of H₂S. From the results of these experiments, it is evident that CoHS⁺ and predominate in the solutions except at 150 °C, for which the dominant chloride complex is CoCl₃⁻. The logarithms of the stability constant for CoHS⁺ show moderate variation with temperature, decreasing from 6.24 at 120 °C to 5.84 at 200 °C, and increasing to 6.52 at 300 °C. Formation constants for chloride species increase smoothly with temperature and at 300°C their logarithms reach 8.33 for , 6.44 for CoCl₃⁻, 4.94 to 5.36 for , and 2.42 for CoCl⁺. Calculations based on the composition of a model hydrothermal fluid (Ksp-Mu-Qz, KCl = 0.25 m, NaCl = 0.75 m, ΣS = 0.3 m) suggest that at temperatures ?200 °C, cobalt occurs dominantly as CoHS⁺, whereas at higher temperatures the dominant species is .  相似文献   

GAIA and Population II Visual Binaries     

Antanas Bartkevičcius  Artūras Gudas 《Astrophysics and Space Science》2002,280(1-2):125-128

The results of a kinematical population classification of 497 Hipparcos orbital binaries are discussed. Less than 10% of the stars from the sample belong to the thick disk. Only seven stars have halo kinematics. There are no direct dynamical mass determinations for extreme halo stars. Some suggestions, concerning Population II visual binaries for which ground-based astrometric observations in combination with GAIA data will be useful in the future for the better determination of orbits for long period Population II binaries, are offered. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Simulating large-scale circulation in seas and oceans     

V.?B.?ZalesnyEmail author  V.?O.?Ivchenko 《Izvestiya Atmospheric and Oceanic Physics》2015,51(3):259-271

The problem of simulating ocean general circulation is considered using an approach developed by G.I. Marchuk. Most attention is focused on problems associated with the application of multi-component-splitting and adjoint-equation methods and with the parameterization of turbulent-exchange processes. The statement of the problem, an algorithm of its solution, and the results of the four-dimensional temperature and salinity data assimilation in a model of World Ocean hydrodynamics are discussed. This algorithm yields qualitatively reliable results, and its main features are modularity, usability, and the possibility of using efficient implicit schemes.  相似文献   

Preface     

Jörg Büchner  Ian Axford  Eckart Marsch  Vytenis Vasyliūnas 《Astrophysics and Space Science》1998,261(1-4):9-10

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A pattern recognition approach to geophysical inversion using neural nets   总被引：3，自引：0，他引：3  

Art Raiche 《Geophysical Journal International》1991,105(3):629-648

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The climate change impact on the water balance of the Curonian Lagoon     

D. Jakimavičius  J. Kriaučiūnienė 《Water Resources》2013,40(2):120-132

The Curonian Lagoon is the biggest fresh water basin in Lithuania influenced by the exchange of the fresh Nemunas and other smaller rivers’ water and saline water of the Baltic Sea. The lagoon ecosystem is influenced by fresh, brackish and brackish water masses. A long-term water balance of the Curonian Lagoon was calculated for the period of 1960–2009. The sum river inflow is 21.784 km³/year, precipitation—1.199 km³/year, evaporation—1.007 km³/year, inflow of brackish water from the Baltic Sea to the Curonian Lagoon—6.171 km³/year, and fresh water runoff from the Curonian Lagoon to the Baltic Sea—27.642 km³/year. The lagoon water balance elements have been influenced by climate change. The water balance forecasting has been performed for the period of 2011–2100. The climate change impact on the water balance of the Lagoon has been evaluated using Global Climate Models (ECHAM5 and HadCM3), greenhouse gas emission scenarios (A2, A1B and B1), and hydrological modelling by Hydrologiska Byrans Vattenbalansavdelning (HBV) software. One scenario was selected for the prediction of the Baltic Sea water level. Considerable changes of the Curonian Lagoon water balance are forecasted in the 21st century. Increase of weather temperature and changes in precipitation will influence the elements of water balance of the Curonian Lagoon. In the period of 2011–2100, the river inflow and outflow from the Baltic Sea into the Lagoon will decrease respectively by 20.4 and 16.6% in comparison with the baseline period (1961–1990). The amount of precipitation and evaporation will increase respectively by 3.8 and 25.1%, while inflow from the Baltic Sea into the Curonian Lagoon will increase up to 39.7% in comparison with the baseline period.  相似文献   

Découverte des roches à affinité ophiolitique dans la chaîne panafricaine au Cameroun : les talcschistes de Ngoung, Lamal Pougue et Bibodi Lamal     

Charles Nkoumbou  Clment Yonta Goune  Frdric Villiras  Daniel Njopwouo  Jacques Yvon  Georges Emmanuel Ekodeck  Flix Tchoua 《Comptes Rendus Geoscience》2006,338(16):1167-1175

Outcrops of talc schists extending over >1 km have been discovered within the garnet- and muscovite-bearing mica schist of the Pan-African belt near Yaoundé (Cameroon). Mineralogical studies show that a metamorphism of the upper greenschist facies was prolonged by hydrothermal reactions. This latter led to the transformation of hornblendites into talc schists. Chemically, talc schists and relicts of hornblendite remind ultrabasic rocks, and REE patterns point to E-MORB and peridotite. It is thus suggested that the talc schists and relicts of hornblendite may correspond to slices of a dismembered Pan-African ophiolite set. To cite this article: C. Nkoumbou et al., C. R. Geoscience 338 (2006).  相似文献   

Chemical weathering rates of a soil chronosequence on granitic alluvium: III. Hydrochemical evolution and contemporary solute fluxes and rates     

Art F. White  Marjorie S. Schulz  Davison V. Vivit  Alex E. Blum  David A. Stonestrom  Jennifer W. Harden 《Geochimica et cosmochimica acta》2005,69(8):1975-1996

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Sediment Budget in Klaipeda Strait     

Gailiušis  B.  Kriaučiūniene  Yu.  Kriaučiūnas  R. 《Water Resources》2003,30(4):379-386

Transport and accumulation of non-cohesive and suspended load in Klaipeda Strait are analyzed. The budget of non-cohesive and suspended load is calculated for the Klaipeda Seaport area under different hydrological conditions. A method is proposed for the forecasting of sedimentation dynamics under anthropogenic changes in the hydrological and morphometric characteristics of the strait caused by the expansion of the Klaipeda Seaport.  相似文献   

A spectrophotometric study of neodymium(III) complexation in chloride solutions     

Art A MigdisovA.E Williams-Jones 《Geochimica et cosmochimica acta》2002,66(24):4311-4323

The formation constants of neodymium complexes in chloride solutions have been determined spectrophotometrically at temperatures of 25 to 250°C and a pressure of 50 bars. The simple ion, Nd³⁺, is dominant at 25°C, whereas NdCl²⁺ and NdCl₂⁺ are the dominant species at elevated temperatures. Equilibrium constants were calculated for the following reactions:Nd³⁺ + Cl⁻ = NdCl²⁺ β₁,Nd³⁺ + 2 · Cl⁻ = NdCl⁺₂ β₂.The values of β₁ were found to be identical within experimental error to the values reported by Gammons et al. (1996) but substantially different from those proposed by Stepanchikova and Kolonin (1999). The values of β₂ obtained in this study agree relatively well with those of Gammons et al. (1996); differences are greatest at intermediate temperature and reach a maximum of one half an order of magnitude at 200°C.Theoretical estimates of β₁ and β₂ by Haas et al. (1995) using the revised Helgeson-Kirkham-Flowers (HKF) equation of state predict lower stability of NdCl²⁺ and NdCl₂⁺ at temperatures above 150°C than determined in this study. A new fit to the HKF equation of state is therefore proposed, which yields values for β₁ and β₂ similar to those obtained experimentally.Using the formation constants reported in this study, we predict that typical seafloor hydrothermal vent fluids will contain a maximum concentration of Nd of ∼2 ppb. This value is several orders of magnitude lower than would be required to explain the levels of Nd mobility commonly reported for seafloor hydrothermal systems and suggests that other ligands may be more important than Cl in transporting rare earth elements in the Earth’s crust.  相似文献