Experimental study of arsenic speciation in vapor phase to 500°C: implications for As transport and fractionation in low-density crustal fluids and volcanic gases     

Gleb S PokrovskiDenis Testemale  Jean-Louis HazemannAndrew Y.u Bychkov  Galina V Golikova 《Geochimica et cosmochimica acta》2002,66(19):3453-3480

The stoichiometry and stability of arsenic gaseous complexes were determined in the system As-H₂O ± NaCl ± HCl ± H₂S at temperatures up to 500°C and pressures up to 600 bar, from both measurements of As^(III) and As^(V) vapor-liquid and vapor-solid partitioning, and X-ray absorption fine structure (XAFS) spectroscopic study of As^(III)-bearing aqueous fluids. Vapor-aqueous solution partitioning for As^(III) was measured from 250 to 450°C at the saturated vapor pressure of the system (P_sat) with a special titanium reactor that allows in situ sampling of the vapor phase. The values of partition coefficients for arsenious acid (H₃AsO₃) between an aqueous solution (pure H₂O) and its saturated vapor (K = mAs_vapor /mAs_liquid) were found to be independent of As^(III) solution concentrations (up to ∼1 to 2 mol As/kg) and equal to 0.012 ± 0.003, 0.063 ± 0.023, and 0.145 ± 0.020 at 250, 300, and 350°C, respectively. These results are interpreted by the formation, in the vapor phase, of As(OH)₃(gas), similar to the aqueous As hydroxide complex dominant in the liquid phase. Arsenic chloride or sulfide gaseous complexes were found to be negligible in the presence of HCl or H₂S (up to ∼0.5 mol/kg of vapor). XAFS spectroscopic measurements carried out on As^(III)-H₂O (±NaCl) solutions up to 500°C demonstrate that the As(OH)₃ complex dominates As speciation both in dense H₂O-NaCl fluids and low-density supercritical vapor. Vapor-liquid partition coefficients for As^(III) measured in the H₂O-NaCl system up to 450°C are consistent with the As speciation derived from these spectroscopic measurements and can be described by a simple relationship as a function of the vapor-to-liquid density ratio and temperature. Arsenic^(III) partitioning between vapor and As-concentrated solutions (>2 mol As/kg) or As₂O₃ solid is consistent with the formation, in the vapor phase, of both As₄O₆ and As(OH)₃. Arsenic^(V) (arsenic acid, H₃AsO₄) vapor-liquid partitioning at 350°C for dilute aqueous solution was interpreted by the formation of AsO(OH)₃ in the vapor phase.The results obtained were combined with the corresponding properties for the aqueous As(III) hydroxide species to generate As(OH)₃(gas) thermodynamic parameters. Equilibrium calculations carried out by using these data indicate that As(OH)₃(gas) is by far the most dominant As complex in both volcanic gases and boiling hydrothermal systems. This species is likely to be responsible for the preferential partition of arsenic into the vapor phase as observed in fluid inclusions from high-temperature (400 to 700°C) Au-Cu (-Sn, -W) magmatic-hydrothermal ore deposits. The results of this study imply that hydrolysis and hydration could be also important for other metals and metalloids in the H₂O-vapor phase. These processes should be taken into account to accurately model element fractionation and chemical equilibria during magma degassing and fluid boiling.  相似文献   

A word about the teacher     

Galina N.Dryomova  Olga V.Eretnova  Tatyana S.Polushina 《天文和天体物理学研究(英文版)》2019,(3):35-46

This is a memorial report on the biography and scientific heritage of M.A. Svechnikov — an outstanding scientist and teacher, the founder of the Ural school of close binary stars and the author of the classification scheme for eclipsing variable stars.  相似文献   

Role of the Rossiter-McLaughlin effect in the study of close binaries     

Galina N.Dryomova  Vladimir V.Dryomov 《天文和天体物理学研究(英文版)》2019,(3):21-30

This paper is devoted to binary stars belonging to the class of eclipsing-variable systems.Photometric and spectroscopic analysis of eclipses allows us to determine geometric parameters of the orbit and physical characteristics of stellar components as well as inclinations of stellar equators to the orbital plane. Estimations of inclinations can be obtained from measurement of the Rossiter-McLaughlin effect, which is discussed using examples of some eccentric binaries with an anomalous apsidal effect. Our task is to find the complete spectrum of solutions of the equation of apsidal motion, depending on the inclinations of the polar axes of the components to the orbital one for these systems, based on their individual spectroscopic and photometric observational data. The matrix of solutions allows us to select those pairs of polar inclinations that provide agreement with the observational apsidal period.  相似文献   

Cenozoic history of the Bering Sea and its northwestern margin     

Vadim Chekhovich  Dmitry Kovalenko  & Galina Ledneva 《Island Arc》1999,8(2):168-180

Tectonic reconstructions based on the geodynamic analysis of geologic, paleomagnetic, structural and kinematic data of Cenozoic age from the western Bering Sea region are proposed in the present paper. The most active tectonic and magmatic processes took place in the Komandorsky segment of the Bering Sea, exemplified by the Late Cretaceous–Early Eocene Olutorsky Arc and Eocene–Oligocene Govena–Karaginsky Arc, which was built on the structures of the Olutorsky Arc. A model of the complex collision of these two arcs with the paleocontinental margin, which considers rotations of the geological blocks from the various structural zones of the western margin of the Bering Sea in the horizontal plane (paleomagnetic data), was proposed by the authors. According to this model the collision of the flanks of the Olutorsky and Govena–Karaginsky arcs took place in the Eocene, before the collision of the central parts in the Miocene.  相似文献   

Winter distribution of euphausiids (Euphausiacea) in the Barents Sea (2000–2005)     

Natalia G. Zhukova  Valentina N. Nesterova  Irina P. Prokopchuk  Galina B. Rudneva 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):1959

The purpose of the study is to analyze the state of the Barents Sea euphausiids populations in the warm period (2000–2005) based on the study of their structure dynamics and distribution under the influence of abiotic and biotic factors. For estimation of their aggregations in the bottom layer, the traditional method was used with the help of the modified egg net (0.2 m² opening area, 564 μm mesh size). The net is used for collecting euphausiids in the autumn–winter period when their activity is reduced, which results in high-catch efficiency. The findings confirmed the major formation patterns of the euphausiids species composition associated with climate change in the Arctic basin. As before, in the warm years, one can see a clear-cut differentiation of space distribution of the dominant euphausiids Thysanoessa genus with localization of the more thermophilic Thysanoessa inermis in the north-west Barents Sea and Thysanoessa raschii in the east. The major euphausiids aggregations are formed of these species. In 2004, the first data of euphausiids distribution in the northern Barents Sea (77–79°N) were obtained, and demonstrated extremely high concentrations of T. inermis in this area, with the biomass as high as 1.7–2.4 g m⁻² in terms of dry weight. These data have improved our knowledge of the distribution and euphausiids abundance during periods of elevated sea-water temperatures in the Barents Sea. The oceanic Atlantic species were found to increase in abundance due to elevated advection to the Barents Sea during the study period. Thus, after nearly a 30-year-long absence of the moderate subtropical Nematoscelis megalops in the Barents Sea, they were found again in 2003–2005. However in comparison with 1960, the north-east border of its distribution considerably shifted to 73°50′N 50°22′E. The portion of Meganyctiphanes norvegica also varied considerably—from 10% to 20% of the total euphausiids population in the warm 1950s–1960s almost to complete disappearing in 1970–1990s. The peak of this species’ occurrence (18–26%) took place in the beginning of warm period (1999–2000) after a succession of cold years. The subsequent reduction of the relative abundance of M. norvegica to 7% might have been mostly caused by fish predation during a period of low population densities of capelin. This high predation pressure may therefore have been mediated both by other pelagic fishes (i.e. herring, blue whiting, polar cod) but also by demersal fishes such as cod and haddock. Similar sharp fluctuations in the capelin stock (the major consumer of euphausiids) created marked perturbations in the food web in the Barents Sea in the middle 1980s and the early 1990s.  相似文献   

Model intercomparison study to investigate a dense contaminant plume in a complex hydrogeologic system     

Mark D. Williams  Charles R. Cole  Michael G. Foley  Galina A. Zinina  Alexander I. Zinin  Nelly A. Vasil'kova  Lilia M. Samsonova 《Environmental Geology》2002,42(2-3):199-213

  相似文献   

Ab initio calculations of 6‐ and 7‐carbon meteoritic amino acids and their diastereomers     

Galina M. CHABAN  Sandra PIZZARELLO 《Meteoritics & planetary science》2010,45(6):1053-1060

Abstract– To better explain the unusual distribution and relative abundances of several 6‐ and 7‐carbon amino acids found in meteorites, their thermodynamic properties were studied using accurate ab initio techniques. In addition to optimized structures and relative energies, vibrational frequency and thermochemical analysis of different diastereomers were performed at temperatures relevant to conditions of synthesis of these amino acids in meteorites. The results of calculations were compared with the measured content of the amino acids in the Murchison meteorite. The distribution of several longer chain amino acids in meteorites seems to point to at least some thermodynamic control in their formation. For diastereomeric compounds, on the other hand, the comparison suggests that their synthetic conditions, or those of their precursors, were far from thermodynamic equilibrium.  相似文献   

The Cretaceous of the East Asian continental margin: Stratigraphy,paleogeography, and paleoclimate     

Galina L. Kirillova 《Island Arc》2011,20(1):57-77

Lithostratigraphic correlation of a 6–10‐km‐thick Aptian–Maastrichtian terrigenous sequence of the East Asian continental margin and Sakhalin and Hokkaido Islands has revealed the existence of a single marine basin. This basin was populated by mixed Tethyan–Boreal fauna and sloped eastward until the Middle Cenomanian. Intense volcanic and tectonic processes caused the uplift of the continental margin in the mid‐Albian to Cenomanian and eastward migration of the shoreline. Paleobotanical studies have discovered a number of climatic changes. Relatively warm conditions existed in the Aptian, changing to cooler conditions in the Early Albian. The maximum warming occurred from the Late Albian to Cenomanian when large‐leaved flowering plants dominated the population. In the Late Cretaceous, the East Asian volcanic belt created a mountain edifice up to 3000 m high, which controlled longitudinal climatic and floral zonation. This control was more efficient than the latitudinal control. A wide development of flowering Platanaceae flora in the Turonian points to a relative cooling. The floral assemblage shows a temperate climate from the Early Coniacian onwards, with an optimum in the Campanian that is consistent with global transgression. As a result of the warm climate, the early Maastrichtian is characterized by highly diverse biota. Furthermore, in the middle Maastrichtian floral and faunal diversity decreased and the seasonal prevalence increased. Cooling occurred in the latest Maastrichtian. Five periods of coal accumulation are recognized throughout the Late Cenomanian to Late Maastrichtian. Shelf, deltaic, and slope turbidite facies of the continental margin contain organic carbon ranging from 0.3% to 2.2%, which together with direct evidence for oil and gas, are believed to be prolific for hydrocarbon exploration.  相似文献   

The radioastronomical “time machine” effect can help the solution of the gamma ray bursts mystery     

Galina V. Lipunova  Ivan E. Panchenko  Vladimir M. Lipunov 《New Astronomy》1997,2(6):555-558

The possible low-frequency radio emission from the progenitors of gamma ray bursts can experience a delay from tens of seconds to hours on the way to the observer due to the dispersion in galactic and extragalactic plasma, and thus reach the observer as a radio afterglow of the burst. This opens a unique possibility (peculiar “time machine”) of seeing what happened at that place before the catastrophe.  相似文献   

Precursory groundwater level changes in the period of activation of the weak intraplate seismic activity on the NE margin of the Bohemian Massif (central Europe) in 2005     

Vladimír Stejskal  Ladislav Kašpárek  Galina N. Kopylova  Alexei A. Lyubushin  Lumír Skalský 《Studia Geophysica et Geodaetica》2009,53(2):215-238

tWe analyse continuous measurements of groundwater level in two deep wells VS-3 and V-28 at the experimental hydro-meteorological station situated on the NE margin of the Bohemian Massif, central Europe, characterized by the weak intraplate seismic activity. The aim of our study is to examine the relationships between changes in the groundwater level and earthquake occurrence. Based on the tidal and barometric response of the water level, we estimated selected elastic parameters of the observed aquifers: the shear modulus G, the Skempton ratio B, the drained matrix compressibility β and the undrained compressibility β_u. Using these parameters and assuming the homogeneous poroelastic material, we derived the sensitivity of the wells to the crustal volume strain. During the observation period from November 1998 to December 2005 we detected in the VS-3 well two pre-seismic steps, related to August 10, 2005 (M = 2.4) and October 25, 2005 (M = 3.3) earthquakes. Amplitudes of the recorded precursory changes (+6 cm and +15 cm) are several times higher than the values predicted from the theoretical precursory crustal strain and the strain sensitivity of the well. Therefore, we presume that the observed pre-seismic water level steps can be attributed to heterogeneity of poroelastic material. We consequently propose the hypothesis of the origin of precursory events based on the presumption of a sensitive site, at which the well is situated.  相似文献