An XPEEM study of structural cation distribution in swelling clays. I. Synthetic trioctahedral smectites     

Delphine Vantelon  Rachid Belkhou  Isabelle Bihannic  Laurent J. Michot  Emmanuelle Montargès-Pelletier  Jean-Louis Robert 《Physics and Chemistry of Minerals》2009,36(10):593-602

X-PEEM images and XPS were collected on isolated layers of three synthetic swelling clays, one hectorite and two saponites with various charge, recording the Si(2p), Al(2p) and Mg(2p) core level spectra from the clay sheets. Spectra were fitted to determine the different components of the core levels. Due to their large full width at half maximum, Si XPS spectra were fitted using two to three doublets. It appears that, for a given clay mineral, Si, Al and Mg binding energies (BE) were constant, for all the observed layers. However, variations of the Si BE were observed depending on the nature of the mineral investigated. The various components obtained from the fit of Si spectra could be assigned to different substitution rates; binding energy shifting to lower values with substitution increase in the layer. Furthermore, variations in Si BE according to charge location were assigned to the influence of exchangeable cation.  相似文献   

Mixing law versus discharge and electrical conductivity relationships: application to an alpine proglacial stream     

Marc Dzikowski  Sylvain Jobard 《水文研究》2012,26(18):2724-2732

Mixing laws have been used in hydrogeology for decades. In glacial hydrology, they are used to determine the contributions of the different reservoirs supplying the proglacial stream. However, some assumptions about discharge–solute matter and discharge–electrical conductivity (EC) relationships have led to erroneous conclusions. Analysis of a theoretical example indicated a hyperbolic relationship between discharge and solute matter concentration/EC for two reservoirs. We applied this approach to experimental data from the Baounet Glacier (Savoie, France), assuming that the proglacial stream is provided by a combination of watershed groundwater flow (diurnally stable and with high EC) and quick drainage from the glacier (low EC and discharge that change very quickly). Applying mixing laws allowed us to characterise these two flows and to separate the quick flows (glacial ablation and rainfalls). Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Regional estimation of catchment‐scale soil properties by means of streamflow recession analysis for use in distributed hydrological models          下载免费PDF全文

Olivier Vannier  Isabelle Braud  Sandrine Anquetin 《水文研究》2014,28(26):6276-6291

The estimation of catchment‐scale soil properties, such as water storage capacity and hydraulic conductivity, is of primary interest for the implementation of distributed hydrological models at the regional scale. This estimation is generally performed on the basis of information provided by soil databases. However, such databases are often established for agronomic uses and generally do not document deep‐weathered rock horizons (i.e. pedologic horizons of type C and deeper), which can play a major role in water transfer and storages. Here, we define the Drainable Storage Capacity Index (DSCI), an indicator that relies on the comparison between cumulated streamflow and precipitation to assess catchment‐scale storage capacities. DSCI is found to be reliable to detect underestimation of soil storage capacities in soil databases. We also use the streamflow recession analysis methodology defined by Brutsaert and Nieber in 1977 to estimate water storage capacities and lateral saturated hydraulic conductivities of the nondocumented deep horizons. The analysis is applied to a sample of 23 catchments (0.2–291 km²) located in the Cévennes‐Vivarais region (south of France). For regionalization purposes, the obtained results are compared with the dominant catchment geology and present a clear hierarchy between the different geologies of the area. Hard crystalline rocks are found to be associated with the thickest and less conductive deep soil horizons. Schist rocks present intermediate values of thickness and of saturated hydraulic conductivity, whereas sedimentary rocks and alluvium are found to be less thick and most conductive. These results are of primary interest in view of the future set‐up of distributed hydrological models over the Cévennes‐Vivarais region. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Quantitative inter‐annual and decadal June–July–August temperature variability ca. 570 BC to AD 120 (Iron Age–Roman Period) reconstructed from the varved sediments of Lake Silvaplana,Switzerland     

Monique M. Stewart  Isabelle Larocque‐Tobler  Martin Grosjean 《第四纪科学杂志》2011,26(5):491-501

Annually resolved June–July–August (JJA) temperatures from ca. 570 BC to AD 120 (±100 a; approximately 690 varve years) were quantified from biogenic silica and chironomids (Type II regression; Standard Major Axis calibration‐in‐time) preserved in the varved sediments of Lake Silvaplana, Switzerland. Using 30 a (climatology) moving averages and detrended standard deviations (mean–variability change, MVC), moving linear trends, change points and wavelets, reconstructed temperatures were partitioned into a warmer (+0.3°C; ca. 570–351 BC), cooler (?0.2°C; ca. 350–16 BC) and moderate period (+0.1°C; ca. 15 BC to AD 120) relative to the reconstruction average (10.9°C; reference AD 1950–2000 = 9.8°C). Warm and variable JJA temperatures at the Late Iron Age–Roman Period transition (approximately 50 BC to AD 100 in this region) and a cold anomaly around 470 BC (Early–Late Iron Age) were inferred. Inter‐annual and decadal temperature variability was greater from ca. 570 BC to AD 120 than the last millennium, whereas multi‐decadal and lower‐frequency temperature variability were comparable, as evident in wavelet plots. Using MVC plots of reconstructed JJA temperatures from ca. 570 BC to AD 120, we verified current trends and European climate model outputs for the 21st century, which suggest increased inter‐annual summer temperature variability and extremes in a generally warmer climate (heteroscedasticity; hotspot of variability). We compared these results to MVC plots of instrumental and reconstructed temperatures (from the same sediment core and proxies but a different study) from AD 1177 to AD 2000. Our reconstructed JJA temperatures from ca. 570 BC to AD 120 showed that inter‐annual JJA temperature variability increased rapidly above a threshold of ～10°C mean JJA temperature. This increase accelerated with continued warming up to >11.5°C. We suggest that the Roman Period serves with respect to inter‐annual variability as an analogue for warmer 21st‐century JJA temperatures in the Alps. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Tree establishment on bars in low‐order gravel‐bed mountain streams     

Isabelle Charron  Edward A. Johnson  Y. E. Martin 《地球表面变化过程与地形》2011,36(11):1522-1533

In many large alluvial rivers, trees often recruit and survive along laterally accreted sediments on bars. This produces a gradient of tree ages and composition with distance from the active channel. However, in low‐order, gravel‐bed mountain streams, such as the stream investigated in this study, it is suggested that vertical accretion results in sediment deposition patterns on bars that are often highly patchy. Consequently, tree species and ages are also heterogeneously distributed, rather than having distinct linear or arcuate banding patterns with distance from the channel. In addition, overall age patterns of trees on these bars follow the distribution of floods, with numerous young trees and few older trees. Recruitment is fairly continuous on these bars and is not correlated with high water years, suggesting that even flows close to bankfull levels are capable of transporting fine sediment to the bars on which trees establish. This pattern of sediment deposition/erosion and the resulting tree recruitment and survival seem to be a result of valley confinement and the lack of lateral accretion in these smaller, mountainous channels. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS. Part 2: application to Taupo Volcanic Zone rhyolites     

Florence?BéguéEmail author  Guilherme?A.?R.?Gualda  Mark?S.?Ghiorso  Ayla?S.?Pamukcu  Ben?M.?Kennedy  Darren?M.?Gravley  Chad?D.?Deering  Isabelle?Chambefort 《Contributions to Mineralogy and Petrology》2014,168(5):1082

Constraining the pressure of crystallisation of large silicic magma bodies gives important insight into the depth and vertical extent of magmatic plumbing systems; however, it is notably difficult to constrain pressure at the level of detail necessary to understand shallow magmatic systems. In this study, we use the recently developed rhyolite-MELTS geobarometer to constrain the crystallisation pressures of rhyolites from the Taupo Volcanic Zone (TVZ). As sanidine is absent from the studied deposits, we calculate the pressures at which quartz and feldspar are found to be in equilibrium with melt now preserved as glass (the quartz +1 feldspar constraint of Gualda and Ghiorso, Contrib Mineral Petrol 168:1033. doi: 10.1007/s00410-014-1033-3. 2014). We use glass compositions (matrix glass and melt inclusions) from seven eruptive deposits dated between ~320 and 0.7 ka from four distinct calderas in the central TVZ, and we discuss advantages and limitations of the rhyolite-MELTS geobarometer in comparison with other geobarometers applied to the same eruptive deposits. Overall, there is good agreement with other pressure estimates from the literature (amphibole geobarometry and H₂O–CO₂ solubility models). One of the main advantages of this new geobarometer is that it can be applied to both matrix glass and melt inclusions—regardless of volatile saturation. The examples presented also emphasise the utility of this method to filter out spurious glass compositions. Pressure estimates obtained with the new rhyolite-MELTS geobarometer range between ~250 to ~50 MPa, with a large majority at ~100 MPa. These results confirm that the TVZ hosts some of the shallowest rhyolitic magma bodies on the planet, resulting from the extensional tectonic regime and thinning of the crust. Distinct populations with different equilibration pressures are also recognised, which is consistent with the idea that multiple batches of eruptible magma can be present in the crust at the same time and can be tapped simultaneously by large eruptive events.  相似文献   

The Geminga fraction     

Alice K. Harding  Isabelle A. Grenier  Peter L. Gonthier 《Astrophysics and Space Science》2007,309(1-4):221-230

Radio-quiet γ-ray pulsars like Geminga may account for a number of the unidentified EGRET sources in the Galaxy. The number of Geminga-like pulsars is very sensitive to the geometry of both the γ-ray and radio beams. Recent studies of the shape and polarization of pulse profiles of young radio pulsars have provided evidence that their radio emission originates in wide cone beams at altitudes that are a significant fraction (1–10%) of their light cylinder radius. Such wide radio emission beams will be visible at a much larger range of observer angles than the narrow core components thought to originate at lower altitude. Using 3D geometrical modeling that includes relativistic effects from pulsar rotation, we study the visibility of such radio cone beams as well as that of the γ-ray beams predicted by slot gap and outer gap models. From the results of this study, one can obtain revised predictions for the fraction of Geminga-like, radio quiet pulsars present in the γ-ray pulsar population.   相似文献   

Error analysis of a new planar electrostatic gravity gradiometer for airborne surveys   总被引：1，自引：1，他引：0  

Karim Douch  Isabelle Panet  Gwendoline Pajot-Métivier  Bruno Christophe  Bernard Foulon  Marie-Françoise Lequentrec-Lalancette  Michel Diament 《Journal of Geodesy》2015,89(12):1217-1231

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Assessing climate change impacts on European wind energy from ENSEMBLES high-resolution climate projections     

Isabelle Tobin  Robert Vautard  Irena Balog  François-Marie Bréon  Sonia Jerez  Paolo Michele Ruti  Françoise Thais  Mathieu Vrac  Pascal Yiou 《Climatic change》2015,128(1-2):99-112

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Distance predicting functions and applied location-allocation models.   总被引：4，自引：0，他引：4  

Dominique Peeters  Isabelle Thomas 《Journal of Geographical Systems》2000,2(2):167-184

Distances between demand points and potential sites for implementing facilities are essential inputs to location-allocation models. Computing actual road distances for a given problem can be quite burdensome since it involves digitalizing a network, while approximating these distances by l _p -norms, using for instance a geographical information system, is much easier. We may then wonder how sensitive the solutions of a location-allocation model are to the choice of a particular metric. In this paper, simulations are performed on a lattice of 225 points using the k-median problem. Systematic changes in p and in the orientation of the orthogonal reference axes are used. Results suggest that the solutions of the k-median are rather insensitive to the specification of the l _p -norm. Received: 12 October 1998/Accepted: 17 September 1999  相似文献