Small droplets from a large meteorite     

Rainer Wieler 《Meteoritics & planetary science》1995,30(3):242-243

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High resolution analysis of uranium and thorium concentration as well as U-series isotope distributions in a Neanderthal tooth from Payre (Ardèche, France) using laser ablation ICP-MS     

Rainer Grün  Maxime Aubert  Marie-Hélène Moncel 《Geochimica et cosmochimica acta》2008,72(21):5278-5290

We have mapped U (²³⁸U) and Th (²³²Th) elemental concentrations as well as U-series isotope distributions in a Neanderthal tooth from the Middle Palaeolithic site of Payre using laser ablation ICP-MS. The U-concentrations in an enamel section varied between 1 and 1500 ppb. The U-concentration maps show that U-migration through the external enamel surface is minute, the bulk of the uranium having migrated internally via the dentine into the enamel. The uranium migration and uptake is critically dependent on the mineralogical structure of the enamel. Increased U-concentrations are observed along lineaments, some of which are associated with cracks, and others may be related to intra-prismatic zones or structural weaknesses reaching from the dentine into the enamel. The uranium concentrations in the dentine vary between about 25,000 and 45,000 ppb. Our systematic mapping of U-concentration and U-series isotopes provides insight into the time domain of U-accumulation. Most of the uranium was accumulated in an early stage of burial, with some much later overprints. None of the uranium concentration and U-series profiles across the root of the tooth complied with a single stage diffusion-adsorption (D-A) model that is used for quality control in U-series dating of bones and teeth. Nevertheless, in the domains that yielded the oldest apparent U-series age estimates, U-leaching could be excluded. This means that the oldest apparent U-series ages of around 200 ka represent a minimum age for this Neanderthal specimen. This is in good agreement with independent age assessments (200-230 ka) for the archaeological layer, in which it was found.The Th elemental concentrations in the dental tissues were generally low (between about 1 and 20 ppb), and show little relationship with the nature of the tissue.  相似文献   

Corrosion-induced gas generation in a nuclear waste repository: Reactive geochemistry and multiphase flow effects   总被引：1，自引：0，他引：1  

Tianfu Xu  Rainer Senger  Stefan Finsterle 《Applied Geochemistry》2008,23(12):3423-3433

Corrosion of steel canisters, stored in a repository for spent fuel and high-level nuclear wastes, leads to the generation and accumulation of H₂ gas in the backfilled emplacement tunnels, which may significantly affect long-term repository safety. Previous studies have used H₂ generation rates based on the volume of the waste or canister material and the stoichiometry of the corrosion reaction. However, Fe corrosion and H₂ generation rates vary with time, depending on factors such as amount of Fe, water availability, water contact area and aqueous and solid chemistry. To account for these factors and feedback mechanisms, a chemistry model was developed related to Fe corrosion, coupled with two-phase (liquid and gas) flow phenomena that are driven by gas-pressure buildup associated with H₂ generation and water consumption. Results indicate that by dynamically calculating H₂ generation rates based on a simple model of corrosion chemistry, and by coupling this corrosion reaction with two-phase flow processes, the degree and extent of gas-pressure buildup could be much smaller compared to a model that neglects the coupling between flow and reactive transport mechanisms. By considering the feedback of corrosion chemistry, the gas pressure increases initially at the canister, but later decreases and eventually returns to a stabilized pressure that is slightly higher than the background pressure. The current study focuses on corrosion under anaerobic conditions for which the coupled hydrogeochemical model was used to examine the role of selected physical parameters on H₂ gas generation and corresponding pressure buildup in a nuclear waste repository. The developed model can be applied to evaluate the effect of water and mineral chemistry of the buffer and host rock on the corrosion reaction for future site-specific studies.  相似文献   

Metal extractability in acidic and neutral mine tailings from the Cartagena-La Unión Mining District (SE Spain)     

Héctor M. Conesa  Brett H. Robinson  Rainer Schulin  Bernd Nowack 《Applied Geochemistry》2008

Mine tailings are ubiquitous in the landscapes of mined areas. Metal solubilities were compared in two chemically distinct mine tailings from the old Mining District of Cartagena-La Unión (SE Spain). One of the tailings was acidic (pH 3.0) with 5400 mg/kg Zn, 1900 mg/kg As and 7000 mg/kg Pb. The other was neutral (pH 7.4) with 9100 mg/kg Zn, 5200 mg/kg Pb and 350 mg/kg As. In samples from the acidic tailings, more than 15% of the Zn and 55% of the Cd were extractable with 0.1 M NaNO₃, and distilled water. In the neutral tailings, using the same reagents, less than 1% of the metals were extractable. A sequential extraction procedure revealed that the sum of the residual and the Fe oxide fractions of Cu, Zn and Pb comprised 80–95% in the acidic tailings and 70–90% in the neutral tailings. The acidic mine tailings had a higher metal solubility, resulting in more metal leaching in the short-term, but also a higher fraction of inert metal. In contrast, in the neutral tailings, the metals were evenly distributed between, oxides and the residual fraction. This implies lower metal mobility in the short-term, but that metal mobility may increase in the long-term. When applied to mine tailings, sequential extractions may provide misleading results because the strong cation exchange capacity of some extractants may induce pH changes and thereby significantly change metal solubility.  相似文献   

Calculations of the seasonal loadings of North Sea sediments with persistent aromatic organochlorines     

Dipl. Ing. Dr. Rainer Knickmeyer  Staatl. gepr. Lebensmittelchem. Oliver Landgraff  Prof. Dr. Hans Steinhart 《Ocean Dynamics》1990,43(6):289-309

The content and distribution of ΣPCB (as the sum of 24 individual components), HCB and p,p′-DDE was determined in sediments taken from the North Sea during two seasons. The mass-balance of aromatic organochlorine compounds in the upper 2 cm of sediments is calculated and dicussed in relation to pollutant dispersal.  相似文献   

Study of inorganic ligand-chromium(III)-surface ternary complexes by ESR spectroscopy     

Laurent Charlet  Rainer Karthein 《Aquatic Sciences - Research Across Boundaries》1990,52(1):93-102

Cr(III) sorbed at the solid/water interface of latex and hectorite was studied by ESR spectroscopy in the presence of different inorganic ligands. The ESR spectra of the surface obtained in the presence of selenite, phosphate and fluoride can be explained in terms of ternary surface complex formation. This is contrasted by the behaviour of sulfate and selenate ions which were found to have no effect on the ligand field of Cr(III), either in the adsorbed state or in solution.  相似文献   

Physical conditions in eruptive prominences at several solar radii     

Rainer M. E. Illing  R. Grant Athay 《Solar physics》1986,105(1):173-190

SMM data from the Corograph/Polarimeter experiment giving intensities of H and continuum emission in eight erupting prominences are analyzed to obtain the physical conditions in the regions of H emission. Since the H intensity depends upon three unknowns whereas only two independent observations are available, it is necessary to assume one additional condition in order to obtain unique solutions. Solutions are chosen that give the maximum expansion of the prominence volume as reflected by minimum values of the electron density. These solutions correspond closely with those giving the best agreement between the gas pressure in the prominence and the ambient coronal pressure. Electron densities are found to be of the order of 10⁸ cm^-3 at temperatures near 2 × 10⁴ K.The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation.  相似文献   

Clay mineral distribution in surface sediments of the South Atlantic: sources, transport, and relation to oceanography   总被引：2，自引：0，他引：2  

Rainer Petschick  Gerhard Kuhn  Franz Gingele 《Marine Geology》1996,130(3-4):203-229

Surface samples, mostly from abyssal sediments of the South Atlantic, from parts of the equatorial Atlantic, and of the Antarctic Ocean, were investigated for clay content and clay mineral composition. Maps of relative clay mineral content were compiled, which improve previous maps by showing more details, especially at high latitudes. Large-scale relations regarding the origin and transport paths of detrital clay are revealed. High smectite concentrations are observed in abyssal regions, primarily derived from southernmost South America and from minor sources in Southwest Africa. Near submarine volcanoes of the Antarctic Ocean (South Sandwich, Bouvet Island) smectite contents exhibit distinct maxima, which is ascribed to the weathering of altered basalts and volcanic glasses. The illite distribution can be subdivided into five major zones including two maxima revealing both South African and Antarctic sources. A particularly high amount of Mg- and Fe-rich illites are observed close to East Antarctica. They are derived from biotite-bearing crystalline rocks and transported to the west by the East Antarctic Coastal Current. Chiorite and well-crystallized dioctaedral illite are typical minerals enriched within the Subantarctic and Polarfrontal-Zone but of minor importance off East Antarctica. Kaolinite dominates the clay mineral assemblage at low latitudes, where the continental source rocks (West Africa, Brazil) are mainly affected by intensive chemical weathering. Surprisingly, a slight increase of kaolinite is observed in the Enderby Basin and near the Filchner-Ronne Ice shelf.

The investigated area can be subdivided into ten, large-scale clay facies zones with characteristic possible source regions and transport paths. Clay mineral assemblages of the largest part of the South Atlantic, especially of the western basins are dominated by chlorite and illite derived from the Antarctic Peninsula and southernmost South America and supported by advection within the Circumantarctic Deep Water flow. In contrast, the East Antarctic provinces are relatively small. Assemblages of the eastern basins north of 30°S are strongly influenced by African sources, controlled by weathering regimes on land and by a complex interaction of wind, river and deep ocean transport. The strong gradient in clay mineral composition at the Brazilian slope indicate a relatively low contribution of tropically derived assemblages to the western basins.  相似文献   

Biosiliceous particle flux in the Southern Ocean     

Andrea Abelmann  Rainer Gersonde 《Marine Chemistry》1991,35(1-4)

The flux of diatom valves and radiolarian shells obtained during short-term and annual sediment trap experiments at seven localities in the Atlantic sector of the Antarctic Ocean (in the Drake Passage, Bransfield Strait, Powell Basin, NW and SE Weddell Sea and the Polar Front north of Bouvet Island) is summarized and discussed. The deployment of time-series sediment traps provided annual flux records between 1983 and 1990. The biosiliceous particle flux is characterized by significant seasonal and interannual variations. Flux pulses, accounting for 70–95% of the total annual flux, occur during austral summer, with a duration ranging between about 2 and 9 weeks. The annual values of vertical diatom and radiolarian flux range between 0.26 × 10⁹ and more than 26 × 10⁹ valves m⁻² and between 0.21 × 10⁴ and 70 × 10⁴ shells m⁻², respectively. Interannual differences in the particle flux range over a factor of 10. Grazers play an important role in controlling the quantity, timing and pattern of the vertical biosiliceous particle flux.The flux pattern of diatoms and radiolarians is similar at most of the sites investigated and shows a close relationship between the production of siliceous phytoplankton and proto-zooplankton. At some sites, however, the radiolarian flux pattern indicates probably phytoplankton production which is not documented by direct signals in the trap record.During their transfer through the water column to the ocean floor, the composition of the biosiliceous particles is altered mechanically (breakdown by grazing Zooplankton) and by dissolution, which significantly affects especially diatoms and phaeodarians in the upper portion of the water column and at the sediment-water interface.Significant lateral transport of suspended biosiliceous particles was observed in the bottom water layer in regions adjacent to shelf areas (Bransfield Strait), and in the vicinity of topographic elevations (Maud Rise), indicating considerable redistribution of biogenic silica in these regions.  相似文献   

Book Review of Advances in Nonlinear Dynamos,by Antonio Ferriz-Mas and Manuel Núñez,The Fluid Mechanics of Astrophysics and Geophysics,Vol. 9, Series Editors A.M. Soward and M. Ghil,Taylor and Francis,London, New York, 2003, IX + 384 pp., £80.00, hardback (ISBN 0-415-28788-X)     

Rainer Hollerbach 《地球物理与天体物理流体动力学》2013,107(5):419-420

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