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91.
Concentration–discharge (CQ) relationships are widely used to assess the link between hydrological and biogeochemical processes at the catchment scale. CQ 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 CQ 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 CQ relationships parameters during the high and low-flow events. The multi-objective calibration can be used for all forms of CQ relationships and avoids issues of under-representation of dilution processes characterized by high-discharge, low-concentration periods.  相似文献   
92.
An investigation of trace metal distributions in the Western Mediterranean Sea was carried out during the RRS Discovery cruise (July 1993) in which a transect from the Strait of Gibraltar to the Strait of Sicily was conducted. Organically complexed dissolved trace metals and their total concentrations were measured to investigate the end-members and to predict the environmental capacity of the Mediterranean for potential toxic metals. The distribution of trace metals can be accounted for by the mixing of several end-members and by some atmospheric inputs to the surface water. For Pb and Fe, the effects of the atmospheric inputs are more pronounced than for the other metals. Due to the rapid exchange of water masses, the Western Mediterranean may have the ability to assimilate the increased external inputs for some trace metals such as Cu, Cd, Ni and Zn. But the external inputs for Pb and Fe exceed the removal capacity of the Western Mediterranean and these elements may accumulate in the water column of the western basin. The C18 Sep-Pak technique and direct determination by DPASV were used to determine the amount of trace metal–organic complexes. The C18 Sep-Pak column isolates only a small fraction of trace metals except for Cu. The maximum hydrophobic fractions for the studied trace metals, except for Cd and Pb, which are not detectable, were found in the subsurface layer at all stations. This maximum may well be linked to picoplankton activity and the picoplankton, prochlorophytes may have an important role in the speciation of dissolved Cu as well as Synechococcus. These organic ligands for Cu were produced at the maximum of biological activity in the Western Mediterranean basin and seem to be accumulated at halocline level by Mediterranean hydrodynamic characteristics. However, direct determination by DPASV showed that the major part of Cu, Cd and Pb, complexed by organic materials, was not isolated by C18 Sep-Pak technique.  相似文献   
93.
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.
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.
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
  相似文献   
96.
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   
97.
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   
98.
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   
99.
A new locality of Messinian fossil fish has been found in the diatomite outcropping in the surroundings of the former “Ferme Giraud”, in the Murdjadjo Massif (near Oran, Algeria). It has yielded an oligospecific fish fauna, including five species indicative of a littoral marine environment that may have occurred in a gulf bottom. This was probably linked to a brackish lagoon, as indicated by the diatom flora.  相似文献   
100.
Swath bathymetric, sonar imagery and seismic reflection data collected during the SOPACMAPS cruise Leg 3 over segments of the Vitiaz Trench Lineament and adjacent areas provide new insights on the geometry and the stuctural evolution of this seismically inactive lineament. The Vitiaz Trench Lineament, although largely unknown, is one of the most important tectonic feature in the SW Pacific because it separates the Cretaceous crust of the Pacific Plate to the north from the Cenozoic lithosphere of the North Fiji and Lau Basins to the south. The lineament is considered to be the convergent plate boundary between the Pacific and Australian Plates during midde to late Tertiary time when the Vitiaz Arc was a continuous east-facing are from the Tonga to the Solomon Islands before the development of the North Fiji and Lau Basins. Progressive reversal and cessation of subduction from west to east in the Late Miocene-Lower Plioene have been also proposed. However, precise structures and age of initiation and cessation of deformation along the Vitiaz Trench Lineament are unknown.The lineament consists of the Vitiaz Trench and three discontinuous and elongated troughs (Alexa, Rotuma and Horne Troughs) which connect the Vitiaz Trench to the northern end of the Tonga Trench. Our survey of the Alexa and Rotuma Troughs reveals that the lineament is composed of a series of WNW-ESE and ENE-WSW trending segments in front of large volcanic massifs belonging to the Melanesian Border Plateau, a WNW trending volcanic belt of seamounts and ridges on Pacific crust. The Plateau and Pacific plate lying immediately north of the lineament have been affected by intense normal faulting, collapse, and volcanism as evidenced by a series of tilted blocks, grabens, horsts and ridges trending N 120° to N100° and N60°–70°. This tectonism includes several normal faulting episodes, the latest being very recent and possibly still active. The trend of the fault scarps and volcanic ridges parallels the different segments of the Vitiaz Trench Lineament, suggesting that tectonics and volcanism are related to crustal motion along the lineament.Although the superficial observed features are mainly extensional, they are interpreted as the result of shortening along the Vitiaz Trench Lineament. The fabric north of the lineament would result from subduction-induced normal faulting on the outer wall of the trench and the zig-zag geometry of the Vitiaz Trench Lineament might be due to collision of large volcanic edifices of the Melanesian Border Plateau with the trench, provoking trench segmentation along left-lateral ENE-WSW trending transform zones. The newly acquired bathymetric and seismic data suggest that crustal motion (tectonism associated with volcanism) continued up to recent times along the Vitiaz Trench Lineament and was active during the development of the North Fiji Basin.  相似文献   
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