THE DETERMINATION OF FLUORINE BY PROTON INDUCED GAMMA RAY EMISSION SPECTROMETRY (PIGE) IN EIGHTEEN CHINESE STANDARD REFERENCE SAMPLES OF STREAM SEDIMENTS, SOILS AND ROCKS: GSD 9-12, GSS 1-8 AND GSR 1-6     

Iwan ROELANDTS  Guy ROBAYE  Panagiotis ALOUPOGIANNIS  Georges WEBER  Jeanne-Marie DELBROUCK-HABARU 《Geostandards and Geoanalytical Research》1987,11(1):79-80

Eighteen new Chinese standard reference samples (including stream sediments, soils and rocks) have been analysed by an automated proton induced gamma ray emission (PIGE) method for fluorine. Results of determinations are reported and are generally in good agreement with the "usable values" previously published.  相似文献   

Tensor structure applied to the least-squares method,revisited     

Georges BLAHA 《Journal of Geodesy》1984,58(1):1-30

The geometrical approach to the least-squares, based on differential geometry with tensor structure and notations, describes the adjustment theory in a simple and plausible manner. The development relies heavily on orthonormal space and surface vectors, and on the extrinsic properties of surfaces linking the two kinds of vectors. In order to relate geometry to adjustments, the geometrical concepts are extended to an n-dimensional space and u- or r-dimensional surfaces, where n is the number of observations, u is the number of parameters in the parametric method and r is the number of conditions in the condition method, with n=u+r. Connection is made to Hilbert spaces by demonstrating that the tensor approach to the least-squares is a classical case of the Hilbert-space approach.  相似文献   

A simple method of magnetic declination fluctuation correction for long single-streamer positioning in a seismic survey     

Victor Martin  Mark S. Noble  Georges Pascal 《Geophysical Prospecting》2004,52(4):351-358

In single‐streamer acquisition, the use of acoustic transducers to constrain the receiver positions is not possible, thus implying the use of compass birds to gather information on the streamer location. The compasses are, however, sensitive to the declination of the local magnetic field of the earth, and local fluctuations not accounted for can degrade the accuracy of reconstructed positions. In order to correct these small‐scale fluctuations, we propose a simple deterministic method to calculate a spatial correction to apply to the compasses that enhances the positioning accuracy. The local compass declination is calculated after a first reconstruction on the whole survey area. This method was applied with success to navigation data from a 3D survey offshore Japan, and the positioning accuracy was improved to the level of the DGPS accuracy.  相似文献   

Precise radiocarbon dating of Late-Glacial cooling in mid-latitude South America     

Irka Hajdas  Georges BonaniPatricio I Moreno  Daniel Ariztegui 《Quaternary Research》2003,59(1):70-78

Variability of atmospheric ¹⁴C content often complicates radiocarbon-based chronologies; however, specific features such as periods of constant ¹⁴C age or steep changes in radiocarbon ages can be useful stratigraphic markers. The Younger Dryas event in the Northern Hemisphere is one of those periods, showing conspicuous ¹⁴C wiggles. Although the origin of those variations is not fully understood, we can make practical use of them and determine: (i) whether the Younger Dryas was global in extent; if so, (ii) were the initial cooling and the final warming synchronous worldwide; and (iii) what are the implications of these similarities/differences? Here we report high-resolution AMS ¹⁴C chronologies from the mid-latitudes of South America that pinpoint a cool episode between 11,400 and 10,200¹⁴C yr B.P. The onset of the final cool episode of the Late Glacial in the southern mid-latitudes, i.e., the Huelmo/Mascardi Cold Reversal, preceded the onset of the Younger Dryas cold event by ∼550 calendar years. Both events ended during a radiocarbon-age plateau at ∼10,200¹⁴C yr B.P. Thus, the Huelmo/Mascardi Cold Reversal encompasses the Younger Dryas, as well as a couple of short-term cool/warm oscillations that immediately preceded its onset in the North Atlantic region.  相似文献   

L'ı̂le de la Dominique, à l'origine des avalanches de débris les plus volumineuses de l'arc des Petites AntillesThe Island of Dominica,site for the generation of the most voluminous debris avalanches in the Lesser Antilles Arc     

Anne Le Friant  Georges Boudon  Jean-Christophe Komorowski  Christine Deplus 《Comptes Rendus Geoscience》2002,334(4):235-243

Results from recent fieldwork and the Aguadomar marine survey in the Lesser Antilles clearly indicate that the volcanic field of southern Dominica has experienced three major edifice collapse events. This led to formation of the most voluminous debris avalanches known in the Caribbean Arc. Submarine hummocky morphology with plurikilometric megablocks is characteristic of debris avalanche deposits. We propose that steep slopes on the western Caribbean side of the island and intense hydrothermal alteration lead to recurrent large-scale edifice collapses. Therefore islands in the Lesser Antilles face a non-negligible risk from generation of tsunamis associated with potential future edifice collapse. To cite this article: A. Le Friant et al., C. R. Geoscience 334 (2002) 235–243.  相似文献   

La biodiversité végétale des gisements d'âge Jurassique supérieur–Crétacé inférieur de Merbah El Asfer (Sud-Tunisien)     

Georges Barale  Mohamed Ouaja 《Cretaceous Research》2002,23(6):707

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Evaluation of TCE and MTBE in situ Biodegradation: Integrating Stable Isotope, Metabolic Intermediate, and Microbial Lines of Evidence     

Jennifer R. McKelvie  Sarah K. Hirschorn  Georges Lacrampe-Couloume  Jon Lindstrom  Joan Braddock  Kevin Finneran  Don Trego  Barbara Sherwood Lollar 《Ground Water Monitoring & Remediation》2007,27(4):63-73

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Suspended sediment and dissolved load budgets of two Amazonian rivers from the Guiana Shield: Maroni River at Langa Tabiki and Oyapock River at Saut Maripa (French Guiana)     

Francis Sondag  Jean Loup Guyot  Jean Sbastien Moquet  Alain Laraque  Georges Adele  Grard Cochonneau  Jean Claude Doudou  Christelle Lagane  Philippe Vauchel 《水文研究》2010,24(11):1433-1445

This study presents the data collected within the framework of an Observatory of Research in Environment on the Amazonian Basin—the ORE HYBAM. It relates to the dissolved and solid loads of the two main rivers of French Guiana, the Maroni and Oyapock rivers, running on the Guiana Shield and draining respectively 64 230 and 24 630 km². The low coefficient of variation of the average annual flows of the two rivers indicates an inter‐annual hydrological stability probably related to the immediate vicinity of the Atlantic Ocean. The sedimentary load is mainly composed of quartz and kaolinite. The total suspended solid (TSS) concentrations are among the world's lowest values; they range from 1 to 130 mg l⁻¹ during the hydrological cycle, with averages of 22 and 12 mg l⁻¹, for the Maroni and Oyapock rivers, respectively. The seasonal variability of these values is significantly higher than that of hydrologic flows, but without simple relationship with the discharge. Water chemical composition of the two rivers indicates a very weak mineralization, very similar to that found in the Amazonian rivers running on the Brazilian and Guianese shields, and in the Congo River and its tributaries in the Central African Shield. Seasonal variations are observed in both basins; they correspond to higher concentrations during low water stage (from October to February) and to more diluted water during the flood, from April to July. A signature enriched in Cl⁻ is present at the Saut Maripa station on the Oyapock River indicating a more marked influence of the trade winds in this basin. The computation of atmospheric contributions to ions budget indicated a weak contribution for Ca²⁺ and Mg²⁺, which originates mainly from water‐rock interactions in both stations, while more than half of Na⁺ is derived from atmospheric inputs. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Effects of waves on the initiation of headland-associated sandbanks     

Nicolas Guillou  Georges Chapalain 《Continental Shelf Research》2011,31(11):1202-1213

Linear sandbanks appear in the lee of coastal headlands where the hydrodynamics are dominated by strong tidal currents and the seabed is characterized by an abundance of sands. They may develop as symmetrical sandbanks on either sides of the headland or as an unique banner bank. The present study numerically investigates the combined effects of waves and tide on the initial development of headland-associated sandbanks. A morphological model based on the coupling of the wave propagation module SWAN (Simulating WAves Nearshore) with the three-dimensional circulation module COHERENS (COupled Hydrodynamical-Ecological model for REgioNal and Shelf seas) is applied to an idealized Gaussian shaped headland for waves conditions varying in heights and directions at the offshore boundary. The coupling considers the effects of the interactions between the wave and current bottom boundary layers, namely the enhanced levels of turbulence near the bottom and the increase of the total bottom shear stress. Waves substantially modify the initial development of sandbanks formed by suspension narrowing their width and reorienting them along the side of the headland. They weakly impact the morphogenesis of sandbanks by bedload favoring on a short-time scale the growth of symmetric circular-shaped features and a central depositional spit prolonging the headland tip. Waves of transverse directions toward the tip of the headland contribute to the initiation by suspension of a well-developed feature in the headland side of low energy limiting the seabed evolution in the exposed area.  相似文献   

Molecular-level modes of As binding to Fe(III) (oxyhydr)oxides precipitated by the anaerobic nitrate-reducing Fe(II)-oxidizing Acidovorax sp. strain BoFeN1     

Claudia Hohmann  Georges Ona-Nguema  Gordon E. Brown Jr.  Andreas Kappler 《Geochimica et cosmochimica acta》2011,75(17):4699-4712

Sorption of contaminants such as arsenic (As) to natural Fe(III) (oxyhydr)oxides is very common and has been demonstrated to occur during abiotic and biotic Fe(II) oxidation. The molecular mechanism of adsorption- and co-precipitation of As has been studied extensively for synthetic Fe(III) (oxyhydr)oxide minerals but is less documented for biogenic ones. In the present study, we used Fe and As K-edge X-ray Absorption Near Edge Structure (XANES), extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, Mössbauer spectroscopy, XRD, and TEM in order to investigate the interactions of As(V) and As(III) with biogenic Fe(III) (oxyhydr)oxide minerals formed by the nitrate-reducing Fe(II)-oxidizing bacterium Acidovorax sp. strain BoFeN1. The present results show the As immobilization potential of strain BoFeN1 as well as the influence of As(III) and As(V) on biogenic Fe(III) (oxyhydr)oxide formation. In the absence of As, and at low As loading (As:Fe ≤ 0.008 mol/mol), goethite (Gt) formed exclusively. In contrast, at higher As/Fe ratios (As:Fe = 0.020-0.067), a ferrihydrite (Fh) phase also formed, and its relative amount systematically increased with increasing As:Fe ratio, this effect being stronger for As(V) than for As(III). Therefore, we conclude that the presence of As influences the type of biogenic Fe(III) (oxyhydr)oxide minerals formed during microbial Fe(II) oxidation. Arsenic-K-edge EXAFS analysis of biogenic As-Fe-mineral co-precipitates indicates that both As(V) and As(III) form inner-sphere surface complexes at the surface of the biogenic Fe(III) (oxyhydr)oxides. Differences observed between As-surface complexes in BoFeN1-produced Fe(III) (oxyhydr)oxide samples and in abiotic model compounds suggest that associated organic exopolymers in our biogenic samples may compete with As oxoanions for sorption on Fe(III) (oxyhydr)oxides surfaces. In addition HRTEM-EDXS analysis suggests that As(V) preferentially binds to poorly crystalline phases, such as ferrihydrite, while As(III) did not show any preferential association regarding Fh or Gt.  相似文献