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11.
Origin of groundwater salinity and hydrogeochemical processes in a confined coastal aquifer: Case of the Rhône delta (Southern France) 总被引：1，自引：0，他引：1
Veronique de Montety Olivier Radakovitch Christine Vallet-Coulomb Bernard Blavoux Daniel Hermitte Vincent Valles 《Applied Geochemistry》2008,23(8):2337-2349
The Rhône delta, South of France (Camargue, 750 km2) is a coastal saline wetland located along the Mediterranean Sea. The confined aquifer of this delta shows high values of electrical conductivity rising from the north (4 mS/cm) to the shoreline (58 mS/cm). This work aims to identify the origin of groundwater salinity and the geochemical processes occurring in this coastal confined aquifer according to the degree of salinity. A natural tracing approach is considered using monthly sampling in 8 piezometers for chemical and isotopic analyses (18O, 2H, 13CTDIC). Ionic and isotopic ratios demonstrate that strong salinities are due to a simple mixing between Mediterranean seawater and freshwater; seawater contribution reaches up to 98% at 8 km from the shoreline. Seawater intrusion induces a particular groundwater chemistry which varies with the degree of seawater contribution: (1) In the less saline part of the aquifer (seawater contribution <20%), the intrusion induces an increase of Na+ in groundwater leading to Ca2+/Na+ exchange processes. The δ13CTDIC analyses show that matrix exchange processes most likely occur for the less saline samples. (2) In the saline part of the aquifer (seawater contribution >20%), the intrusion induces SO4 reduction which is confirmed by highly depleted δ13CTDIC values (up to −19‰). The δ13CTDIC also reveals that methanogenesis processes may occur in the most reductive part of the aquifer. Due to SO4 reduction, the intrusion induces a shift in carbonate equilibrium leading to supersaturation with respect to dolomite and/or magnesian calcite. Thus carbonate precipitation may occur in the area strongly influenced by seawater. 相似文献
12.
Veronique Louvel Jérôme Dyment Jean-Claude Sibuet 《Geophysical Journal International》1997,128(1):188-196
The deep seismic reflection profile Western Approaches Margin (WAM) cuts across the Goban Spur continental margin, located southwest of Ireland- This non-volcanic margin is characterized by a few tilted blocks parallel to the margin. A volcanic sill has been emplaced on the westernmost tilted block. The shape of the eastern part of this sill is known from seismic data, but neither seismic nor gravity data allow a precise determination of the extent and shape of the volcanic body at depth. Forward modelling and inversion of magnetic data constrain the shape of this volcanic sill and the location of the ocean-continent transition. The volcanic body thickens towards the ocean, and seems to be in direct contact with the oceanic crust. In the contact zone, the volcanic body and the oceanic magnetic layer display approximately the same thickness. The oceanic magnetic layer is anomalously thick immediately west of the volcanic body, and gradually thins to reach more typical values 40 km further to the west. The volcanic sill would therefore represent the very first formation of oceanic crust, just before or at the continental break-up. The ocean-continent transition is limited to a zone 15 km wide. The continental magnetic layer seems to thin gradually oceanwards, as does the continental crust, but no simple relation is observed between their respective thinnings. 相似文献
13.
干涉SAR中地球形状与去平地效应的关系 总被引：2，自引：1，他引：2
从分析合成孔径雷达干涉处理过程中的水平地形效应入手，通过分析地形差异所导致的相位变化，得出了对于不同轨道参数的卫星去水平地形效应时地球形状的影响是不同的结论。并从理论上证明对于ERS-1和2卫星数据可以不必考虑地球形状，即可以默认大地是水平的。 相似文献
14.
Juan Rofes Sophie Cersoy Antoine Zazzo Aurelien Royer Pierre-Yves Nicod Veronique Laroulandie Mathieu Langlais Yvan Pailler Celine Leandri Franck Leandri Matthieu Lebon Anne Tresset 《第四纪科学杂志》2020,35(4):505-513
Frequently preserved in archaeological and palaeontological sites, the tiny size of small-mammal remains favours percolations into underlying layers along stratigraphic sequences. This is one of the various post-depositional processes that may affect the integrity of the original deposits and therefore the subsequent scientific interpretations. Recent developments in sample preparation offer the possibility of detecting intrusive episodes through the absolute dating of minute amounts of bone (down to 10 mg), meaning that isolated elements (such as mandibles in this case) are sufficient to obtain reliable radiocarbon dates if collagen is moderately to well preserved. The radiocarbon dates obtained here for small-mammal bones (recovered from pre-Bølling to recent deposits) and their comparison with previous dates obtained from other sources (large-mammal bones, charcoal, botanical samples, etc.), with different protocols and instruments, illustrate the potential of small-mammal dating to reveal (and eventually contribute a solution to) stratigraphical issues in different archaeological contexts. 相似文献
15.
The purpose of this research is to propose a laboratory method based on attrition and sieving for the treatment of runoff water sediments in the aim of developing a pilot unit. The attrition process serves to remove fine particles and pollutants from the surface of coarse stormwater sediment particles. In all cases, the efficiency of pollutant removal is dependent upon various parameters, including cutoff threshold, residence time, solid density, temperature and impeller speed. This article presents the optimization of these various parameters along with method efficiency; for this work, several sediments have been tested. The results indicate that an attrition scrubber may be effectively used to remediate contaminated sediment and that reuse is definitely possible. A model of the method will also be proposed to study the behavior of fine particles and pollutants. 相似文献
16.
Charles W. Querfeld Raymond N. Smartt Veronique Bommier Egidio Landi Degl'innocenti Lewis L. House 《Solar physics》1985,96(2):277-292
The Stokes components of He i D3 emission in two quiescent prominences, using full spectral profile measurements, are analyzed to derive vector magnetic fields. Two independently developed schemes, based on the Hanle effect, are used for interpretation. They involve solutions of the statistical equilibrium equations for the He i D3 multiplet, including the effect of coherency and full level crossing, which predict the magnetic field dependence of the observed polarization. Derived magnetic field vector solutions for each pair of linear polarization Stokes profiles corresponding to an observational point in the prominence are, intrinsically, not uniquely determined, and a set of possible solutions is usually obtained. However, mutual consistency of these solutions with those independently predicted by the form of the circular polarized component, allow, in almost all cases, rejection of all solutions of a set except one symmetrical pair. Of such a pair, a unique solution can be determined with a high confidence level by reference to independent potential field information. Field vectors are found usually to be close to horizontal and normal to the prominence surface, but extreme exceptions are found. Field values range from 6 G to 60 G. The derived vectorfield configurations and their magnitudes are briefly discussed relative to these prominences and to different quiescent prominence models.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation. 相似文献
17.
R. Grant Athay Charles W. Querfeld Raymond N. Smartt Egidio Landi Degl'innocenti Veronique Bommier 《Solar physics》1983,89(1):3-30
Observations of linear polarization in two resolved components of HeI D3 are interpreted using the Hanle effect to determine vector magnetic fields in thirteen prominences. As in all vector magnetic field measurements, there is a two-fold ambiguity in field direction that is symmetric to a 180° rotation about the line-of-sight. The polar angles of the fields show a pronounced preference to be close to 90° from the local solar radius, i.e., the field direction is close to horizontal. Azimuth angles show internal consistency from point to point in a given prominences, but because of the rotational symmetry, the fields may be interpreted, in most cases, as crossing the prominence either in the same sense as the underlying photospheric fields or in the opposite sense. An exceptionally well observed large prominence of approximately planar geometry exhibits no measurable change in the vector magnetic field either with height or with location along the prominence axis. A second well observed large prominence overlying a sharply curved magnetic neutral line, when interpreted assuming that the prominence field has the same sense as the photospheric field, shows a rotation in the azimuth angle of the field relative to the observer by about 150° and relative to the local plane of the prominence by about 65°. In the alternative interpretation in which the prominence field has the opposite sense of the photospheric field, the field still rotates by 150° relative to the observer but remains essentially constant with respect to the plane of the prominence. This prominence erupted shortly after the extended observations. One good quality observation during the course of the eruption gives a vector field fully consistent with the pre-eruption field in the same segment of the prominence. 相似文献
18.
A rhodamine dye tracer study was conducted over eight tidal cycles to investigate mixing and tidal exchange processes in Perch Pond, a Cape Cod embayment subject to recurrent blooms of the toxic dinoflagellate, Gonyaulax tamarensis. Dye injected at the inlet to Perch Pond during flood tide became well-mixed within the pond in one day and was removed at an effective first order rate of 0.36 d?1, equivalent to a 70% utilization of the maximum possible tidal exchange. This relatively high flushing efficiency can be attributed to a density-driven circulation within the pond, consisting of a subsurface inflow of high salinity dense water on the flood tide followed by removal of lighter surface layers through the shallow inlet during ebb tide. The formation of a frontal convergence near the inlet on flood tide is consistent with the observed distribution of G. tamarensis cysts and shelifish toxicity. It is also clear that phytoplankton like G. tamarensis, whose maximum growth rates approximate the rate of tidal flushing, can only bloom within the embayment by avoiding the outflowing surface waters. Mixing within the pond is probably less efficient and population losses greater during dry periods when the pond salinity is higher and the stratification weaker. 相似文献
19.
This review provides explanations of how geodesy, rotation and gravity can be addressed using radioscience data of an orbiter around a planet or of the lander on its surface.The planet Mars is the center of the discussion.The information one can get from orbitography and radioscience in general concerns the global static gravitational field, the time variation of the gravitational field induced by mass exchange between the atmosphere and the ice caps, the time variation of the gravitational field induced by... 相似文献
20.
The planet Mars has many Earth like characteristics, but its evolution is different. An important future step in Mars’ geophysics is to deploy a network of stations at the surface of Mars inorder to study a wide range of properties of this planet, going from its deep interior structure to its atmosphere. Each ground station (small landers) will contain the same scientific instruments/experiments. The collected data will improve our knowledge of the Martian interior, surface and atmosphere, as well as its evolution. An important part of these objectives can only be achieved by a network of surface stations, as a network gives unique possibilities for performing studies of global scale phenomena and studies requiring simultaneous measurements from several sites. 相似文献