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排序方式: 共有261条查询结果,搜索用时 78 毫秒
1.
Josep M. Trigo‐Rodriguez Jordi Llorca Jiri Borovi
ka Juan Fabregat 《Meteoritics & planetary science》2003,38(8):1283-1294
Abstract— Relative chemical abundances of 13 meteoroids were determined by averaging the composition of the radiating gas along the fireball path that originated during their penetration into the Earth's atmosphere. Mg, Fe, Ni, Cr, Mn, and Co abundances, relative to Si, are similar to those reported for CI and CM carbonaceous chondrites and interplanetary dust particles. In contrast, relative abundances of Ca and Ti in meteor spectra indicate that these elements suffer incomplete evaporation processes. The chemical composition of all meteoroids studied in this work differs from that of 1P/Halley dust. 相似文献
2.
The passivation of calcite by acid mine water. Column experiments with ferric sulfate and ferric chloride solutions at pH 2 总被引:2,自引:1,他引:1
Josep M. Soler Marco Boi Jos Luis Mogolln Jordi Cama Carlos Ayora Peter S. Nico Nobumichi Tamura Martin Kunz 《Applied Geochemistry》2008,23(12):3579-3588
Column experiments, simulating the behavior of passive treatment systems for acid mine drainage, have been performed. Acid solutions (HCl or H2SO4, pH 2), with initial concentrations of Fe(III) ranging from 250 to 1500 mg L−1, were injected into column reactors packed with calcite grains at a constant flow rate. The composition of the solutions was monitored during the experiments. At the end of the experiments (passivation of the columns), the composition and structure of the solids were measured. The dissolution of calcite in the columns caused an increase in pH and the release of Ca into the solution, leading to the precipitation of gypsum and Fe–oxyhydroxysulfates (Fe(III)–SO4–H+ solutions) or Fe–oxyhydroxychlorides (Fe(III)–Cl–H+ solutions). The columns worked as an efficient barrier for some time, increasing the pH of the circulating solutions from 2 to 6–7 and removing its metal content. However, after some time (several weeks, depending on the conditions), the columns became chemically inert. The results showed that passivation time increased with decreasing anion and metal content of the solutions. Gypsum was the phase responsible for the passivation of calcite in the experiments with Fe(III)–SO4–H+ solutions. Schwertmannite and goethite appeared as the Fe(III) secondary phases in those experiments. Akaganeite was the phase responsible for the passivation of the system in the experiments with Fe(III)–Cl–H+ solutions. 相似文献
3.
The Simpevarp area is one of the alternative sites being considered for the deep geological disposal of high level radioactive waste in Sweden. In this paper, a coupled regional groundwater flow and reactive solute transport model of the Simpevarp area is presented that integrates current hydrogeological and hydrochemical data of the area. The model simulates the current hydrochemical pattern of the groundwater system in the area. To that aim, a conceptual hydrochemical model was developed in order to represent the dominant chemical processes. Groundwater flow conditions were reproduced by taking into account fluid-density-dependent groundwater flow and regional hydrogeologic boundary conditions. Reactive solute transport calculations were performed on the basis of the velocity field so obtained. The model was calibrated and sensitivity analyses were carried out in order to investigate the effects of heterogeneities of hydraulic conductivity in the subsurface medium. Results provided by the reactive transport model are in good agreement with much of the measured hydrochemical data. This paper emphasizes the appropriateness of the use of reactive solute transport models when water-rock interaction reactions are involved, and demonstrates what powerful tools they are for the interpretation of hydrogeological and hydrochemical data from site geological repository characterization programs, by providing a qualitative framework for data analysis and testing of conceptual assumptions in a process-oriented approach. 相似文献
4.
Optimizing interpolation of shoot density data from a Posidonia oceanica seagrass bed 总被引:1,自引:0,他引:1
Michele Scardi Lorenzo A. Chessa Eugenio Fresi Antonio Pais & Simone Serra 《Marine Ecology》2006,27(4):339-349
A case study on the optimization of Posidonia oceanica density interpolation, using a data set from a large meadow at Porto Conte Bay (NW Sardinia, Italy), is presented. Ordinary point kriging, cokriging and a weighted average based on inverse square distance were used to interpolate density data measured in 36 sampling stations. The results obtained from different methods were then compared by means of a leave‐one‐out cross‐validation procedure. The scale at which interpolation was carried out was defined on the basis of the Hausdorff dimension of the variogram. Optimizing spatial scale and data points search strategy allowed obtaining more accurate density estimates independently of the interpolation method. 相似文献
5.
D. Rouan N. Epchtein M. De Muizon F. Lacombe P. Puget D. Tiphene F. Boulanger X. Desert G. Guyot L. D'Hendecourt J -M. Lamarre A. Leger F. Pajot J -L. Puget E. Caux M. Giard G. Serra C. Cesarsky L. Vigroux A. Omont 《Astrophysics and Space Science》1994,217(1-2):41-44
Proposed to both the French and the European Space Agency as one possible small mission, SPICE is a project for a dedicated small satellite for a near-IR spectroscopic all-sky survey. The instrument would cover the spectral range 1.8 - 3.6µm, possibly extended to 1.8 - 7µm, at a resolution of 100, with pixels of 1 arc-min. The excellent sensitivity (0.02 MJy sr-1) results from: i) the quasi-zero level of background due to the efficient passive cooling of the whole experiment; ii) the use of large format arrays; iii) the non-stop observing mode (drift-scanning). The spectral domain, complementing the one of ISO, partially opaque from the ground, is specially rich in spectral features tracing stars and all components of the Interstellar Medium (molecular, atomic and ionized gas, dust). With a cooling below 80 K of the focal instrument, then it becomes possible to consider doubling the spectral domain and to cover the whole 1.8 - 7µm range. 相似文献
6.
C. Bartolini A. Bonifazi F. D'antona F. Fusi Pecci L. Oculi A. Piccioni R. Serra 《Astrophysics and Space Science》1982,83(1-2):287-310
The evolutionary status of hydrogen-poor stars is analyzed.Photoelectric observations of six objects are reported as a first step of a long-term project devoted to search for variability of a large sample of hydrogen-poor stars.The observed stars show phenomena of microvariability with an amplitude of the order of 0m. 1 or less.Two extreme helium stars have been examined: a period in the range of 0d.162-0d.164 has been found for BD+ 1002179, andP=0d.1079962 for BD+1303324.The mass-losing O subdwarf (sdO) BD+370 443 presents short-term fluctuations with a time-scale of several minutes and long-term variations on a scale of months. The standard sdO BD+750325 is probably non-variable, although light variations of very small amplitude (m0.03) with a time-scale of about 1 hr might be present. The high gravity sdO BD+2504655, which is very close to the white dwarf stage, also presents variability on a time-scale of about 13 minutes, and might be an analog of the recently discovered pulsating sdO, or hot white dwarf, PG 1159-035.The variability of the intermediate helium star HD 37776 is finally confirmed. 相似文献
7.
By use of known published values forT
eff, logg, andM
v, a check on our procedure for determining the physical parameters of A v-type stars from Strömgren photometry has been performed. External errors for our calculated physical parameters have been obtained.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
8.
Gilles Levresse Jordi Tritlla Janet Villareal Eduardo Gonzalez-Partida 《Journal of Geochemical Exploration》2006,89(1-3):205
Fluorite deposits are widespread in northern Mexico and those deposits have traditionally been categorized as exclusively hydrothermal–magmatic in origin. Recently, two different fluorite-bearing type models have been proposed for the Northern Mexican deposits: (1) MVT-like deposits formed from basinal brines mobilized during the Laramide Orogeny (La Encantada deposit, Gonzalez-Partida et al., [Gonzalez-Partida, E., Carrillo-Chavez, A., Grimmer, J.O.W., Pironon, J., 2002. Petroleum-rich fluid inclusions in fluorite, Purisima mine, Coahuila, Mexico. International Geological Review 44 (8), 751–763.]; Tritlla et al., [Tritlla, J., Gonzalez-Partida, E., Levresse, G., Banks, D., Pironon, J., 2004. Fluorite deposits at Encantada-Buenavista, Mexico: products of Mississippi Valley type processes — a reply. Ore Geology Reviews 25, 329–332.]); and (2) fluorite-bearing skarns in close contact with rhyolite intrusives (Levinson, [Levinson, A.A., 1962. Beryllium–fluorine mineralization at Aguachile Mountain, Coahuila, Mexico. American Mineralogist 47, 67–75.]). The El Pilote fluorite deposit falls into the second category, and is the only known example of a magmatic-related fluorite deposit in the area. The fluorite trace-element patterns from both the El Pilote skarn and La Encantada MVT deposits display comparable and very low relative abundances as well as comparable chondrite-normalized REE patterns; this would suggest that the skarn F-source comes from the remobilization of a MVT fluorite manto. 相似文献
9.
10.
Audrey GalvéAlfred Hirn Jiang MeiJosep Gallart Béatrice de VoogdJean-Claude Lépine Jordi DiazWang Youxue Qian Hui 《Earth and Planetary Science Letters》2002,203(1):35-43
New wide-angle reflection and refraction seismic data provide constraints on the structure of the upper lithosphere, and test models of its evolution to raise the northeastern part of the Tibetan Plateau. Amplitudes observed for reflections from the crust-mantle boundary are sufficiently large to suggest that there is no significant partial melt in the deep crust. The data show an increase of the crustal thickness between terranes from north of the Kun Lun Fault into the Qang Tang of central Tibet, and a contrast among their intracrustal images and compositions. In the north, P and S velocities are consistent with a dominantly felsic composition and show that only the upper crust thickened. South of the Kun Lun Fault a thicker crust made of two layers could result from the superposition of the originally thin crust of the Bayan Har terrane on the lower part of the crust of the domain to the north, which upper crust it shoved and thickened. Different modes of crustal thickening, either by thickening of individual layers or superpositions and imbrication among them appear to work jointly to raise the topography. 相似文献