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91.
José Manuel Tunqui Neira Vazken Andréassian Gaëlle Tallec Jean-Marie Mouchel 《水文研究》2021,35(11):e14428
Concentration–discharge ( ) relationships are widely used to assess the link between hydrological and biogeochemical processes at the catchment scale. relationships are mainly calibrated using mono-objective methods to represent, either concentrations or discharge-weighted concentrations (i.e., load). Based on its wide use in hydrological modelling, we test a multi-objective calibration for the relationship parameters, using both concentration and load, and compare it to a mono-objective calibration applied on either concentrations or load. This work is carried out on a high-frequency dataset (ORACLE-Orgeval Observatory, France). Our findings show that the multi-objective calibration yield a better representation of relationships parameters during the high and low-flow events. The multi-objective calibration can be used for all forms of relationships and avoids issues of under-representation of dilution processes characterized by high-discharge, low-concentration periods. 相似文献
92.
Laurie Biscara Thierry MulderPhilippe Martinez François BaudinHenri Etcheber Jean-Marie JouanneauThierry Garlan 《Marine and Petroleum Geology》2011,28(5):1061-1072
In order to define the nature and distribution of the organic matter (OM) preserved in the modern Ogooué deep sea turbidite system (Gabon), bulk geochemical techniques (Rock-Eval pyrolysis, elemental and isotopic analyses) and palynofacies were applied to three piston cores collected in the Cape Lopez Canyon and lobe and on the continental slope, north of the canyon.The hemipelagic sedimentation in the study area is characterized by high accumulations of well-preserved OM (∼2-3 wt. TOC %). Bulk geochemical and palynofacies analysis indicate both a marine and terrestrial origin of the OM. Contribution of the marine source is higher on the slope than in the canyon and lobe.OM accumulation in turbidites is strongly controlled by the combined influence of the Cape Lopez Canyon and littoral drift. In the canyon and lobe, turbidites show generally low TOC content (0.5 wt. %) and OM is oxidized. The origin of the OM is interpreted as both marine and terrestrial, with a higher contribution of continental source versus marine source. The low TOC contents are due to the large siliciclastic fraction transported by the littoral drift and diverted in the Cape Lopez Canyon during high energy processes (e.g. storms) which tend to dilute the OM in the turbidites. Transport by long-shore currents and/or turbiditic flows leads to oxidation of the OM.On the continental slope located north of the Cape Lopez Canyon, large amounts of OM are deposited in turbidites (up to 14 wt. %). The OM is predominantly derived from terrestrial land plants and has not been subjected to intense oxidation. These deposits are characterized by high hydrocarbon potential (up to 27 kg HC/t rock), indicating a good potential as gas-prone source rock. Because Cape Lopez Canyon captures a significant part of the sediment transported by the littoral drift, the siliciclastic sedimentary flux is reduced north of the canyon; OM is thus concentrated in the turbidites. Variation in TOC content within turbidite laminae can be explained by the burst and sweep deposition process affecting the boundary layer of the turbulent flow.This study confirms that gravity flows play a preponderant role in the accumulation and preservation of OM in deep water and that deep sea turbidite systems could be regarded as an environment where organic sedimentation occurs. 相似文献
93.
Mohamed Younes Ahmed Said Taibi Hanène Souli Jean-Marie Fleureau 《Geotechnical and Geological Engineering》2013,31(4):1335-1348
The use of electro-osmosis in geotechnical engineering has been considered since 1930. Its application has been tested in several sectors like the fight against rising damp in porous materials, the consolidation of soils as well as the remediation of the soils contaminated by oil and heavy metals, etc. The paper presents an experimental study of the electrokinetic phenomena resulting from the application of an electric field to argillaceous sandstones. The electroosmotic tests required the development of a completely new experimental device composed of a confining cell, of a system of measurement and control of the pH of the electrolyte near the electrodes, of a system of control and measurement of the voltage and current at the edges of the sample, and of a system of measurement of inlet (anodic) and outlet (cathodic) flows. Various boundary conditions are considered with and without control of pH. In addition, a micro structural modelling of the electrokinetic phenomena makes it possible to quantify the electro osmotic conductivity with a good agreement with experiments. 相似文献
94.
Brigitte Schmieder Nicole Mein Yuanyong Deng Cristiana Dumitrache Jean-Marie Malherbe Joachim Staiger E. E. Deluca 《Solar physics》2004,223(1-2):119-141
This paper is focused on the formation of two filaments in a complex center of decaying active regions (AR 8329 and AR 8326), located in the northern hemisphere. The observations were obtained in Hα by the Multi-channel Subtractive Double Pass spectrograph (MSDP mounted on the German telescope VTT in Tenerife) and EUV lines with TRACE (Transition Region And Corona Explorer). High Doppler shifts are found to be related to the ends of filament segments where canceling magnetic fields are also located (as seen on magnetograms from Big Bear Solar Observatory). At these locations, velocities along the line of sight, derived by using a cloud model method reach −20 km s−1, the segments of filaments merge and frequently a time-related sub-flare is observed by TRACE. The chirality of the filament segments has been determined by different methods: the segments of dextral chirality join together and form a long dextral filament, and a single filament of sinistral chirality forms end to end with the dextral filament but does not merge with it. Assuming a model of twisted flux tube for filament material, we suggest that the dextral filament has negative helicity and a relationship between its formation and the close by sunspot with the same sign of helicity. 相似文献
95.
Eric H. Oelkers Jacques Schott Jean-Marie Gauthier Teresa Herrero-Roncal 《Geochimica et cosmochimica acta》2008,72(20):4948-4961
Steady-state muscovite dissolution rates have been measured at temperatures from 60 to 201 °C and 1 ? pH ? 10.3 as a function of reactive solution K, Si, and Al concentration. The pegmatitic muscovite used in these experiments has a composition consistent with (Na0.09, K0.86)Fe0.05Al2.92Si3.05O10(OH1.95, F0.06). All experiments were performed in titanium mixed-flow reactors. All experiments were performed at far-from-equilibrium conditions with respect to muscovite. All reactive solutions were undersaturated with respect to secondary product phases other than for some experiments which were supersaturated with respect to bohemite and diaspore; steady-state dissolution was stoichiometric for all experiments that were undersaturated with respect to these phases.The variation of rates with reactive solution composition depends on the solution pH. At pH ? 7 rates were found to decrease significantly with increasing reactive fluid Al activity but be independent of aqueous SiO2 activity. pH < 7 rates measured in the present study from 60 to 175 °C are consistent with
96.
Aurélia Mouret Pierre Anschutz Pascal Lecroart Gwénaëlle Chaillou Christelle Hyacinthe Jonathan Deborde Frans J. Jorissen Bruno Deflandre Sabine Schmidt Jean-Marie Jouanneau 《Geo-Marine Letters》2009,29(3):133-149
Manganese is a major redox reactive element of benthic metabolism. We have built a database of existing knowledge on the benthic
geochemistry of Mn in the Bay of Biscay, in order to comprehensively assess the behaviour of Mn in a variety of environments
during early diagenesis. The database contains vertical profiles of particulate and dissolved Mn species of 59 cores collected
during 17 cruises between 1997 and 2006 at nine stations positioned between 140 and 4,800 m water depths. At all studied stations,
Mn species follow the conventional distribution, where Mn(III,IV) species are enriched in the oxic layer, and dissolved Mn
is present in the anoxic sediments. A minor part of Mn-oxides originates from sedimenting particles. The major part is of
diagenetic origin, and derives from the oxidation of upward-diffusing dissolved Mn(II). Mn-oxide inventories are higher at
the deeper stations than at the shallower ones. This difference cannot be attributed to different sources of sedimenting particles,
but it must depend on sedimentation rate and diagenetic processes. At depth, dissolved Mn(II) concentrations are constant.
This probably reflects equilibrium with an authigenic Mn(II) phase, which is the ultimate phase into which Mn is fossilized.
The Mn content of deeper anoxic sediments is similarly low in all the cores studied, associated with corresponding trends
of Mn content in sedimenting particles of the Bay of Biscay. Bioturbation, rather than redox oscillations, can convey Mn(III,IV)
species downwards into the anoxic sediments where they are reduced, associated with a peak of dissolved Mn. Because dissolved
Mn(II) is re-oxidized when it diffuses towards the oxic layer, the inventory of the diagenetic Mn(III,IV) phase remains at
steady state, especially at stations where the oxic layer is thick. It then becomes possible to calculate the residence time
of diagenetic Mn(III,IV) particles within the oxic layer, using the upward-directed flux of pore water Mn(II). By applying
this residence time to the accumulation of sediments within the oxic layer, we obtain the sediment mass accumulation rate.
The values calculated for the sediments of the Bay of Biscay fit well with accumulation rates obtained from radionuclides
or sediment traps. The method has also been validated with data collected in other marine sedimentary environments.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
97.
Christian Ruby Mustapha Abdelmoula Aurélien Renard Georges Ona-Nguema Jean-Marie R. Génin 《Geochimica et cosmochimica acta》2010,74(3):953-966
FeII-III hydroxycarbonate green rust GR(CO32−), FeII4 FeIII2 (OH)12 CO3·3H2O, is oxidized in aqueous solutions with varying reaction kinetics. Rapid oxidation with either H2O2 or dissolved oxygen under neutral and alkaline conditions leads to the formation of ferric oxyhydroxycarbonate GR(CO32−)∗, FeIII6 O12 H8 CO3·3H2O, via a solid-state reaction. By decreasing the flow of oxygen bubbled in the solution, goethite α-FeOOH forms by dissolution-precipitation mechanism whereas a mixture of non-stoichiometric magnetite Fe(3−x)O4 and goethite is observed for lower oxidation rates. The intermediate FeII-III oxyhydroxycarbonate of formula FeII6(1−x) FeIII6x O12 H2(7−3x) CO3·3H2O, i.e. GR(x)∗ for which x ? [1/3, 1], is the synthetic compound that is homologous to the fougerite mineral present in hydromorphic gleysol; in situ oxidation accounts for the variation of ferric molar fraction x = [FeIII]/{[FeII]+[FeIII]} observed in the field as a function of depth and season but limited to the range [1/3, 2/3]. The domain of stability for partially oxidized green rust is observed in the Eh-pH Pourbaix diagrams if thermodynamic properties of GR(x)∗ is compared with those of lepidocrocite, γ-FeOOH, and goethite, α-FeOOH. Electrochemical equilibrium between GR(x)∗ and FeII in solution corresponds to Eh-pH conditions close to those measured in the field. Therefore, the reductive dissolution of GR(x)∗ can explain the relatively large concentration of FeII measured in aqueous medium of hydromorphic soils containing fougerite. 相似文献
98.
Martine Mullet Sophie BoursiquotMustapha Abdelmoula Jean-Marie GéninJean-Jacques Ehrhardt 《Geochimica et cosmochimica acta》2002,66(5):829-836
Tetragonal FeS1−x mackinawite, has been synthesized by reacting metallic iron with a sodium sulfide solution and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), transmission Mössbauer spectroscopy (TMS) and X-ray photoelectron spectroscopy (XPS). Based on XRD and TEM analyses, synthetic mackinawite exhibits crystallization and is identical to the natural mineral. Unit cell parameters derived from XRD data are a = b = 0.3670 nm and c = 0.5049 nm. The bulk Fe:S ratio derived from the quantitative dispersive energy analysis is practically 1. XPS analyses, however, showed that mackinawite surface is composed of both Fe(II) and Fe(III) species bound to monosulfide. Accordingly, monosulfide is the dominant S species observed at the surface with lesser amount of polysulfides and elemental sulfur. TMS analysis revealed the presence of both Fe(II) and Fe(III) in the mackinawite structure, thus supporting the XPS analysis. We propose that the iron monosulfide phase synthesized by reacting metallic iron and dissolved sulfide is composed of Fe(II) and S(-II) atoms with the presence of a weathered thin layer covering the bulk material that consists of both Fe(II) and Fe(III) bound to S(-II) atoms and in a less extent of polysulfide and elemental sulfur. 相似文献
99.
Hossein Mehdizadeh Jean-Michel Liotard Jean-Marie Dautria 《Comptes Rendus Geoscience》2002,334(2):111-117
Lavas of the Quaternary Damavand volcano (Central Alborz, Northern Iran) have been analysed for major and trace elements. The shoshonitic character of this magmatic series is definitively confirmed and most samples correspond to banakites. The Nb, Ta and Ti negative anomalies observed in all lavas suggest that they derive from of a sub-continental lithosphere metasomatised in a subduction setting. Their variable trace element enrichments are explained both by mineral fractionation and by crustal contamination in a shallow magmatic chamber. To cite this article: H. Mehdizadeh et al., C. R. Geoscience 334 (2002) 111–117. 相似文献
100.
Élizabeth L. Simms Alvin E. Simms & Jean-Marie M. Dubois 《Geografiska Annaler: Series A, Physical Geography》1997,79(3):167-176
A method of analysis was developed to estimate wind-induced wave heights in the coastal zone. The analysis is based on a digital bathymetry model in raster format. The model uses wind characteristics such as direction, velocity, and fetch. In addition, underwater terrain slope magnitude and orientation, and water depth are used in the computation of the model to estimate wave heights. Two analyses are shown, taking into account waves built from short fetch wind and indefinite fetch wind. The analysis was applied to Hare Bay in northern Newfoundland. First, we take into account a northerly wind of 6.9 ms−1 where the fetch is 19 km or less. The estimated wave heights vary between 0 and 0.5 m. With the second application, we considered an indefinite ESE fetch wind of 17.8 ms−1 . In this case, the wave heights resulting from the application of the model vary between 0 and 11.8 m. We compared the modelling results based on ESE wind and the wave energy derived through visual analysis. Relationships were identified between the wave height classes and the wave energy categories. 相似文献