Magnetosheath Structure in an Anisotropic Plasma Model     

Bruno P. Besser  Mikhail I. Pudovkin  Valentina V. Lebedeva  Svetlana A. Zaitseva  Claudia-Veronika Meister 《Astrophysics and Space Science》2000,274(1-2):399-405

Variations of the magnetic field and plasma parameters across the Earth's magnetosheath are calculated for an anisotropic plasma in the Chew-Goldberger-Low approximation. Additionally, proton pitch-angle diffusion is taken into account as the energy transfer mechanism between the direction perpendicular and parallel to the magnetic field. We discuss the main characteristics of the magnetic barrier for different temperature relaxation times and their dependence on the interplanetary magnetic field orientation. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Low-temperature hydrothermal deposits in the rift zone of the Mid-Atlantic Ridge     

Yu. A. Bogdanov  I. V. Vikent’ev  A. Yu. Lein  O. Yu. Bogdanova  A. M. Sagalevich  A. V. Sivtsov 《Geology of Ore Deposits》2008,50(2):119-134

New data on the low-temperature hydrothermal deposits of the Snake Pit, TAG, Broken Spur, and Lucky Strike fields in the rift valley of the Mid-Atlantic Ridge (MAR) obtained during the 47th cruise of the R/V Akademik Mstislav Keldysh are reported. These deposits are related to focused and diffuse flows of hydrothermal solutions and the material precipitated from hydrothermal plumes. Electron microscopy study allowed us to identify protoferrihydrite, ferrihydrite, goethite, hematite, Mn-feroxyhyte, and Fe-vernadite. Fe-free vernadite, akaganeite, opal, nontronite, lepidocrocite, and jarosite occur in subordinate amounts. Bacteria-like forms made up of protoferrihydrite particles replaced with ferrihydrite, nontronite, and goethite along with particles of Fe-free vernadite and opal were found. The contents of major, minor, and noble metals were determined in samples with AAS, INAA, and the direct chromatographic method. Elevated PGE contents were established in the low-temperature hydrothermal deposits of the MAR for the first time. The highest PGE contents were detected in the inner zone of Fe-Mn crusts on the surface of a hydrothermal chimney in the Snake Pit field ((ppm) 0.13 Pd, 0.12 Rh, and 0.03 Pt, along with 16.5 Au, 642 Ag, and 355 Se) and in the Au-depleted crust on the surface of a sulfide ore fragment in the Lucky Strike field (0.12 ppm Pd and 0.04 ppm Rh along with 0.03 ppm Au, 683 ppm Se, and 1.5 wt % Ba).  相似文献   

Subgrade-reinforcement techniques for the dangerously deforming sections of railway lines in the north of the Russian Far East     

Alexey Piotrovich  Svetlana Zhdanova 《寒旱区科学》2017,9(3):197-204

This paper lists difficult railway construction conditions that are typical for the northern areas of the Russian Far East. Permafrost-bound issues of railway and highway construction and operation are described. Some of the authors'' developments for subgrade stabilization in the foregoing conditions are given as examples.  相似文献   

Authigenic gold formation in the cyanidation tailings of gold–arsenopyrite–quartz ore of Komsomolsk deposit (Kuznetski Alatau,Russia)     

Maksim V. Kirillov  Svetlana B. Bortnikova  Olga L. Gaskova 《Environmental Earth Sciences》2016,75(13):1050

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Expected geological and geomorphological risks along the Northern Sea Route     

S. L. Nikiforov  L. I. Lobkovskii  N. N. Dmitrevskii  R. A. Ananiev  N. O. Sorokhtin  A. V. Khortov  O. Yu. Bogdanova 《Doklady Earth Sciences》2016,466(1):75-77

Degradation of the underwater multiyear permafrost rocks (UMPR) together with intensification of thermal abrasion processes in the coasts are global risks on a planetary scale. Changes in the physical properties of sediments can occur after degradation of the UMPR and can lead to unpredictable consequences especially in the regions of technical development. Drifting ice bottom exaration (ice plucking of bottom sediments), which is increasing based on the data of recent expeditions, is no less dangerous. These processes are hazardous for practically all types of activity.  相似文献   

Pyrrhotite mineralization as a search criterion for sulfide deposits at sediment-covered spreading centers     

O. Yu. Bogdanova  A. Yu. Lein  O. M. Dara  E. G. Ozhogina  A. P. Lisitzin 《Doklady Earth Sciences》2016,470(1):928-932

Pyrrhotite ores forming the hydrothermal vents of the Hydrothermal Hills in the Southern Trough of the Guaymas depression were studied. A series of features pointing to the occurrence of surface and buried sulfide deposits of pyrrhotite mineralization was revealed: the presence of pyrrhotite associations to hydrocarbons of oil series; low concentrations of Cu, Zn, and Pb; the enrichment of sulfur of pyrrhotite and hydrogen sulfide of hydrothermal solutions in heavy ³⁴S isotope by 5–7%; and the heavy isotope composition of carbon in naphthoid compounds. The results obtained allow one to suggest searching for large sulfide deposits at active rifts of high spreading and sedimentation rates, i.e., at near-continental rifts of the humid zone of avalanche sedimentation.  相似文献   

Mobilization of metals from riverine suspended matter in seawater   总被引：1，自引：0，他引：1  

Vladimir M. Shulkin  Natalia N. Bogdanova 《Marine Chemistry》2003,83(3-4):157

Suspended matter from rivers in the Russian Far East was leached by seawater to assess the extent of Zn, Cd, Pb, and Cu release from the land-derived solids to estuarine and coastal waters. The concentration of solids in the leaching experiments was 0.25 g/l. The suspended matter used varied in metal content from background levels to heavily contaminated.The concentration of Zn, Cd, Pb, and Cu in the leaching solution after 1, 4, 24, 48, and 96 h was determined by anodic stripping voltammetry. Measurable Cd was transferred from river suspended matter to seawater with both background and elevated Cd concentrations, though the amount of Cd released was different. The increase in Zn and Pb in solution was observed only at the enriched concentration of metals in the suspended solids. The Cu transfer into solution was more pronounced from material with elevated Cu concentration, but the amount of degradable organic matter in the solid phase was more important.The losses of metals from the riverine solids varied from 60% to 80% of total concentration for Cd to negligible for Pb, independent of contamination. The Zn loss depended on the initial concentration in the solids and decreased from 11–16% for the heavily contaminated suspended matter to 3–8% for the moderately enriched ones and to negligible for the pristine solids. Cu loss varied from 1% to 30% of total content, with no clear dependence on concentration in the suspended matter.The significance of additional input of dissolved metals to estuarine and coastal waters from remobilization was assessed by comparison with the initial concentration of dissolved metals in river water. Such experiments could be used to assess the water quality impact of atmospheric fallout of contaminated solids and storm drainage from the urbanized areas, in addition to river suspended matter studies.  相似文献   

Fluxes of iron and manganese across the sediment–water interface under various redox conditions     

Svetlana V. Pakhomova  Per O.J. Hall  Mikhail Yu. Kononets  Alexander G. Rozanov  Anders Tengberg  Andrei V. Vershinin 《Marine Chemistry》2007

Fluxes of dissolved forms of iron and manganese across the sediment–water interface were studied in situ in the Gulf of Finland and the Vistula Lagoon (Baltic Sea), and in the Golubaya Bay (Black Sea) from 2001 to 2005. Fluxes were measured using chamber incubations, and sediment cores were collected and sliced to assess the porewater and solid phase metal distribution at different depths. Measured and calculated benthic fluxes of manganese and iron were directed out of sediment for all sites and were found to vary between 70–4450 and 5–1000 µmole m^− 2 day^− 1 for manganese and iron, respectively. The behavior of the studied metals at various redox conditions in the near-bottom water and in the sediment was the main focus in this study. Our results show the importance of bottom water redox conditions for iron fluxes. We measured no fluxes at oxic conditions, intermediate fluxes at anoxic conditions (up to 200 μmole m^− 2 day^− 1) and high fluxes at suboxic conditions (up to 1000 μmole m^− 2 day^− 1). Total dissolved iron fluxes were generally dominated by iron(II). Contribution of iron(III) to the total iron flux did not exceed 20%. Obtained fluxes of manganese at all studied regions showed a linear correlation (r² = 0.97) to its concentration in the porewater of the top sediment layer (0–5 mm) and did not depend on dissolved oxygen concentrations of bottom water. Organically complexed iron and manganese were in most cases not involved in the benthic exchange processes.  相似文献   

Advanced methods for correcting measured precipitation and results of their application in the polar regions of Russia and North America     

E. G. Bogdanova  B. M. Il’in  S. Yu. Gavrilova 《Russian Meteorology and Hydrology》2007,32(4):229-244

The WMO recommendations on solid precipitation correction, based on generalized results of precipitation gauge intercomparisons performed in 1985–1996, do not take into account systematic errors in precipitation measurements such as wind-induced at high winds and false precipitation blown by wind into the precipitation gauge during strong blizzards at low temperatures, typical of high latitudes. To eliminate these biases in solid precipitation measurements in the Arctic latitudes, special procedures are proposed for three different national methods of precipitation measurement in Russia, the United States (Alaska), and Canada. Differences in the correction methods in these countries are caused by differences in the design of instruments, observation technique, climate, and content of data archives for calculating the measurement errors. Results of application of the proposed procedures for precipitation correction in the Arctic regions of the above-mentioned countries are discussed. The results are compared against the maps of corrected precipitation in the world water budget and snow, ice resources atlases and in the Handbook for Climate of the USSR.  相似文献   

Variation in the number of days with heavy precipitation on the territory of Russia for the period of 1936–2000     

E. G. Bogdanova  S. Yu. Gavrilova  B. M. Il’in 《Russian Meteorology and Hydrology》2010,35(5):344-348

Time variations in the number of days with heavy precipitation based on data of 93 stations on the territory of Russia are analyzed. Time series of precipitation, corrected by the elimination of main systematic errors of their measurement at the level of their diurnal sums, are used, when computing. The diurnal precipitation sum, exceeding the average long-term diurnal precipitation maximum by three times, was taken as the threshold quantitative criterion, defining “the day with heavy precipitation” concept. This value varies within 10–15 mm/day on the territory of Russia. Extremums fluctuate from 5 to 40 mm/day. Absolute values of linear trends of the annual number of days with heavy precipitation are comparatively small, they fluctuate within ±4 days on the whole territory of Russia. In relative terms, these variations are rather significant, reaching ±40% and more of the corresponding average value for 65 years. The comparison of the spatial distribution of characteristics of linear trends of the annual number of days with heavy precipitation and annual precipitation sum indicates their close conformity.  相似文献