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Olivier Pourret Aline DiaMélanie Davranche Gérard GruauOdile Hénin Maxime Angée 《Applied Geochemistry》2007
Ultrafiltration experiments using new small ultracentifugal filter devices were performed at different pore size cut-offs to allow the study of organo-colloidal control on metal partitioning in water samples. Two shallow, circumneutral pH waters from the Mercy site wetland (western France) were sampled: one dissolved organic carbon (DOC)- and Fe-rich and a second DOC-rich and Fe-poor. Major- and trace-element cations and DOC concentrations were analysed and data treated using an ascendant hierarchical classification method. This reveals the presence of three groups: (i) a “truly” dissolved group (Na, K, Rb, Ca, Mg, Ba, Sr, Si and Ni); (ii) an inorganic colloidal group carrying Fe, Al and Th; and (iii) an organic colloidal group enriched in Cr, Mn, Co, Cu and U. However, REE and V have an ambivalent behaviour, being alternatively in the organic pool and in the inorganic pool depending on sample. Moreover, organic speciation calculation using Model VI were performed on both samples for elements for which binding constants were available (Ca, Mg, Ni, Fe, Al, Th, Cr, Cu, Dy, Eu). Calculation shows relatively the same partitioning of these elements as ultrafiltration does. However, some limitations appear such as (i) a direct use of ultrafiltration results which tends to overestimate the fraction of elements bound to humic material in the inorganic pool as regards to model calculations as well as, (ii) a direct use of speciation calculation results which tends to overestimate the fraction of elements bound to humic material in the organic pool with regard to ultrafiltration results. Beside these limitations, one can consider that both techniques, ultrafiltration and speciation calculation, give complementary information, especially for more complex samples where inorganic and organic colloids compete. 相似文献
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Richard Giot Sylvie Granet Maxime Faivre Nadia Massoussi Julie Huang 《Geomechanics and Geoengineering》2018,13(4):246-263
A transversely isotropic thermo-poroelastic constitutive law is developed and implemented in the finite element code Code_Aster (EDF, France). It is then validated using an analytic solution for an inclined borehole in a transversely isotropic medium. A strategy for identifying the parameters of the transversely isotropic thermo-poroelastic model based on an inverse method is proposed on the basis of different laboratory tests. To demonstrate the efficiency and applicability of the model, it is then applied in a three-dimensional numerical model of an underground structure in a parameter sensitivity study. The results of the modelling highlight the importance of accounting for anisotropic phenomena when determining the dimensions of underground facilities. The whole approach is presented in the paper, from model development to application to 3D numerical modelling to an engineering case study. 相似文献
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Didier Lahondère Florence Cagnard Guillaume Wille Jéromine Duron Maxime Misseri 《Environmental Earth Sciences》2018,77(10):385
This paper provides new mineralogical and morphological characterizations of calcic amphiboles from hydrothermally altered dolerites from France to discuss their potential to contain naturally occurring asbestos (NOA) and to release elongated mineral particles corresponding to asbestos fibers, or asbestos-like fibers, into the air. The calcic amphiboles were characterized using electron microprobe analysis, scanning and transmission electron microscopy. The results underline that fibrous occurrences of actinolite and ferro-actinolite regularly occur in hydrothermally altered dolerites, both in the groundmass and in quartz veins. In the groundmass, actinolitic amphiboles crystallize at the expense of magmatic clinopyroxenes and are rarely fibrous. Conversely, actinolite and ferro-actinolite fibers from quartz veins are potentially asbestiform to clearly asbestiform. The identification of quartz veins in hydrothermally altered dolerites is, therefore, an important parameter which should draw attention to the possible presence of asbestiform actinolite fibers. The mineralogical characterization of such veins as well as the estimation of their thickness and density is an important point to consider during studies involving NOA issues. Moreover, the degree of weathering of the dolerites, which directly affects the ability of non-asbestiform actinolite crystals to dissociate into very thin fibers, regarded as cleavage fragments instead of as asbestos, is also a key parameter to consider. Hydrothermally altered dolerites are common rocks likely to be exploited by the quarrying industry to produce aggregates or to be affected by construction works. Due to the abundance of actinolite fibers that they may contain locally, these rocks become priority targets to be monitored in terms of geological characterization and airborne fiber emission to ensure the protection of populations and workers. 相似文献
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Laura Airaghi Nicolas Bellahsen Benoît Dubacq David Chew Claudio Rosenberg Emilie Janots Maxime Waldner Valérie Magnin 《Journal of Metamorphic Geology》2020,38(2):183-204
Pre-kinematic greenschist facies metamorphism is often observed in granites and basement units of mountain belts, but rarely dated and accounted for in orogenic cycle reconstructions. Studying pre-kinematic alteration is challenging because of its usual obliteration by subsequent syn-kinematic metamorphism often occurring at conditions typical of the brittle–ductile transition. It is, however, to be expected that pre-kinematic alteration has major implications for the rheology of the upper crust. In the 305 Ma-old Variscan basement of the Bielsa massif (located in the Axial Zone of the Pyrenees), successive fluid–rock interaction events are recorded in granites below 350°C. Combined microstructural and petrographic analysis, low-T thermobarometry and in situ U–Th/Pb dating of anatase, titanite and monazite show extensive pre-orogenic (pre-Alpine) and pre-kinematic alteration related to feldspar sericitization and chloritization of biotite and amphibole at temperatures of 270–350°C at 230–300 Ma. This event is followed by a second fluid–rock interaction stage marked by new crystallization of phyllosilicates at 200–280°C and is associated with the formation of mylonitic shear zones and fractures parallel to the shear planes. U–Pb anatase and monazite ages as well as the microtextural relationships of accessory minerals suggest an age for this event at 40–70 Ma, consistent with independent regional geology constraints. The Variscan basement was therefore softened at late to post-Variscan time, at least 150–200 Ma before the main Alpine shortening while Alpine-age compression (c. 35–50 Ma) leads to the formation of a dense net of mylonites. The associated deformation, both distributed at the scale of the Bielsa massif and localized at decametric scale in mylonitic corridors, precedes the strain localization along the major thrusts of the Axial Zone. The Bielsa massif is a good example where inherited, pre-orogenic upper crustal softening controls the deformation patterns in granitic basement units through low-grade metamorphic reactions. 相似文献
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Maxime C. Bridoux 《Geochimica et cosmochimica acta》2010,74(14):4044-1574
Long-chain polyamines (LCPAs) constitute a new family of natural organic compounds that have recently been isolated and characterized from the biosilicified cell walls of diatom cultures. To date, diatom-specific polyamines have not been investigated from the marine environment and their fate in the environment is entirely unknown. Here, we report a series of LCPAs in a diatom frustule-rich sediment core (TNO57-13 PC4), originating from the Atlantic sector of the Southern Ocean and spanning from the Holocene to the Last Glacial Maximum (LGM). Liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS) revealed a complex mixture of linear polyamines with at least 28 individual molecular species. Ion trap mass fragmentation studies, combined with high resolution Time of Flight (TOF) mass spectrometry showed that the polyamine pool consisted of a series of N-methylated propylamine compounds attached to a putrescine moiety, with individual LCPAs varying in chain length and degree of methylation. The structural similarity between LCPAs extracted from the diatom-rich sediment core and those extracted from the frustules of cultured diatoms suggests that sedimentary LCPAs are derived from diatom frustules. We hypothesize that these intrinsically labile organic molecular fossils are protected from diagenesis by encapsulation within the frustule. These compounds constitute a new class of biomarkers that could potentially be indicators of diatom species distribution. Isotopic analysis of LCPAs could be used to improve age models for sediment cores that lack calcium carbonate and to improve current interpretations of diatom-based paleoproxies, including diatom-bound nitrogen isotopes. 相似文献
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Assessment of the impact of pools on the water isotopic signature of a boreal patterned peatland 
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下载免费PDF全文 Recent studies have shown that boreal peatlands exhibit considerable chemical variability but without clear spatial pattern. This chemical heterogeneity illustrates the complex hydrological behaviour of peatlands, particularly patterned fen. Isotopic, chemical and physical tracers were used to describe the hydrological behaviour of a small boreal headwater catchment (13 ha) during the snow‐free period with a special emphasis on the downstream patterned fen. Results showed that shallow pools were mixed every day during the summer, particularly during nights or discharge periods. Despite large water storage capacities in pools, which should induce large buffer effect, hydrological behaviour of patterned fen is more similar to a piston flow process. This is probably because of the division of the fen into successive small cascading streamflow reservoirs. The consequences were a rapid change of the chemical signature throughout the fen, particularly upstream. A spatial pattern was observed downstream in early summer. The isotopic signature passed from an upstream depleted and homogeneous signature to a progressively enriched downstream signature. However, this pattern was not identified during the wetter period (late summer), probably because the discharge, which dominated the water budget, decreased the surface water residence time and flushed a large proportion of stored surface water. We developed for this patterned fen a conceptual model of the surface flow to explain these particular mixing effects and the implications on the dynamics of the chemical signature. To further our understanding of similar boreal headwater catchments, future work should include the development of a multiple mixed‐reservoir model. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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The drainage of Lake Ojibway in glaciolacustrine sediments of northern Ontario and Quebec,Canada 下载免费PDF全文
下载免费PDF全文 Virginie Daubois Martin Roy Jean J. Veillette Maxime Ménard 《Boreas: An International Journal of Quaternary Research》2015,44(2):305-318
Physical evidence for the drainage of glacial lakes remains relatively rare in depositional records, giving rise to much debate on the location of outlets and discharge pathways, as well as on the climate impact of the attendant meltwater forcing. Lake Ojibway developed following the withdrawal of the Laurentide Ice Sheet in northern Ontario and Quebec, Canada. The late‐stage evolution of this large ice‐dammed lake was influenced by the complex dynamics of the retreating ice margin, which highly complicates the identification of the termination of Lake Ojibway in glaciolacustrine sediment records. Here, we document the composition of sections of rhythmites that contain in their upper part an anomalously thick and whitish bed (10–15 cm) that is in turn overlain by ～1 m of faintly bedded rhythmites. Grain‐size analyses showed that the thick whitish bed consists primarily of fine to coarse silt (2–63 μm), contrasting with the lower and upper rhythmites that are largely dominated by clay (<2 μm). The detrital carbonate content of the thick silt bed is characterized by consistently high values (2.5 to 2.8%), whereas the bounding rhythmites show lower and highly variable values. Oxygen isotope measurements further show a marked change going from typical glacial meltwater values (～ ?29.6 to ?27.7‰; VSMOW) for the lower rhythmites and the silt bed to modern‐like meteoric values (?18.4 to ?14.6‰) for the uppermost rhythmites. These data suggest that this marker bed may be associated with a major drawdown event that possibly corresponds to the final drainage of Lake Ojibway. AMS radiocarbon dating of ostracods extracted from the drainage bed also documents an important hardwater effect within the Ojibway basin. 相似文献
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Etienne Balan Emmanuel Fritsch Thierry Allard Guillaume Morin Maxime Guillaumet Simon Delattre Marc Blanchard Georges Calas 《Comptes Rendus Geoscience》2011,343(2-3):177-187
This article summarizes some recent results obtained on the physical properties of environmental minerals, mostly kaolinite-group minerals and Fe- and Al-(hydr)oxides occurring in lateritic soils. The defective structure of these minerals, including impurities, stacking faults and radiation-induced defects, is probed using infrared spectroscopy and electron paramagnetic resonance. Resulting information bears on models of soil formation and transformation mechanisms of minerals in low-temperature environments. We underline the increasing impact of quantum chemical modeling in this field, providing straightforward interpretations of spectroscopic signals and overcoming the limits of fingerprint approaches. Importantly, the first-principles modeling of isotopic fractionation factors provides new links between mineralogical and geochemical investigations of secondary minerals. 相似文献