2014 |
Balter, V., and N. Vigier. "Natural variations of lithium isotopes in a mammalian model." Metallomics 6 (2014): 582.
Résumé : Despite lithium’s extensive clinical applications, the cellular and molecular basis for the therapeutic effects remains to be elucidated. The large difference in mass between the two lithium isotopes (6Li and 7Li) has prompted biochemists to explore the metabolism of Li by using pure 6Li and 7Li labeled drugs.
However, experiments were carried out at very high Li concentrations, which did not reflect natural conditions. In the present study, we consider, for the first time, the natural variations of the 7Li/6Li ratio in the organs and body fluids of an animal model, sheep. Each organ seems to be characterized by a specific Li isotope composition. So far, the range of the 7Li/6Li ratio in the sheep body, expressed as d permil variations relative to the L-SVEC standard (d7Li), is about 40%, between muscles (B40%) and kidney (B0%). Relative to a dietary d7Li value of B+17%, serum, red blood cells, muscle, liver, brain and kidney have a 7Li enrichment of 12%, 14%, +22%, +5%, 3% and 15%, respectively. The Li isotope
composition is likely to be fractionated during intestinal absorption, with a greater absorption of 6Li relative to 7Li. According to previous conclusions obtained with 6Li and 7Li labeled chemicals, 6Li appears to diffuse into erythrocytes faster than does 7Li. However, this does not hold for myocytes and hepatocytes, because these two tissues have a higher d7Li level than serum. Purely diffusive isotopic fractionation would leave all organs 7Li-depleted relative to the serum, which is not the case, suggesting that active, molecule-specific, isotopic fractionation occurs in the body. Our preliminary results suggest that natural Li isotope variations can shed light on its regulation in the body, being active or passive.
Mots-clés : cac
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Blard, P. H., J. Lavé, K. A. Farley, V. Ramirez, N. Jimenez, L. C. P. Martin, J. Charreau, B. Tibari, and M. Fornari. "Progressive glacial retreat in the Southern Altiplano (Uturuncu volcano, 22°S) between 65 and 14 ka constrained by cosmogenic 3 He dating." Quaternary Science Reviews 82 (2014): 209–221.
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Davenport, J., G. Caro, and C. France-Lanord. "Tracing silicate weathering in the Himalaya using the 40K-40Ca system: A reconnaissance study." Procedia Earth and Planetary Science 10 (2014): 238–242.
Résumé : Himalayan erosional system. To this end, we present high precision 40Ca data on river sediments, dissolved river loads and whole-rock carbonates representative of the main tectonic units of the Himalayas. Our results show that metamorphosed
dolomites from the Lesser Himalaya (LH) exhibit no radiogenic 40Ca excess despite highly variable 87Sr/86Sr signatures (0.73-0.85). In contrast, silicate material is radiogenic, with ε40Ca ranging between +1 in the TSS to +4 ε-units in the LH. Preliminary results obtained from a series of 27 Himalayan rivers show that ε40Ca in the dissolved load is significantly influenced by silicate lithologies, with ε40Ca ranging from +0.1 to +1.6 ε-units. Our results suggest that the 40Ca signature of Himalayan rivers primarily reflects the lithological nature of their erosional source, and highlights the potential of the 40K-40Ca decay scheme as a
tracer of silicate weathering.
Mots-clés : cac
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Gabitov, R. I., C. Rollion-Bard, A. Tripati, and A. Sadekov. "In situ study of boron partitioning between calcite and fluid at different crystal growth rates." Geochimica et Cosmochimica Acta 137 (2014): 81–92.
Résumé : The boron isotopic and chemical content of carbonates (expressed as d11B and B/Ca ratios) have been proposed as proxies for seawater carbonate system parameters. Thermodynamic and kinetic effects on d11B and B partitioning are not yet fully
constrained, underscoring the importance of exploring possible effects of growth rate on boron incorporation in synthetic calcium carbonate minerals, which is the focus of this study. Secondary Ion Mass Spectrometry (SIMS) measurements of
B/Ca and d11B were performed on single crystal of calcite synthesized by diffusion of CO2 under controlled conditions from a solution of NH4Cl–CaCl2 doped with boron. Growth rates of calcite (V, nm/s) within crystals grown isothermally at 24.6 C were monitored by sequentially spiking calcite-precipitating fluids with rare earth element (REE) dopants. The REE were analyzed with SIMS at spots that match those locations where B/Ca and d11B ratios were measured. Values for the boron Nernst partition coefficient, defined as DB = B(calcite)/B(fluid), increase from 0.5 (pHNBS = 8.15) to 0.9 (pH = 8.00) with values of V increasing from 0.04 to 0.13 nm/s. For d11B behavior, it was not possible to draw conclusive results due to the analytical error (2.2&; 2r). pH effects on DB during calcite precipitation, associated with an increase in pH from 8.00 to 8.15, appear to
be masked by the competing effects of changing V. We conclude that over the range of growth rates and other conditions investigated in this study, growth rate effects on B partitioning need to be accounted for when using B/Ca ratios in biogenic calcite as a proxy for seawater carbonate system parameters.
Mots-clés : cac
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Jomelli, V., V. Favier, M. Vuille, R. Braucher, L. C. P. Martin, P. H. Blard, C. Colose, D. Brunstein, F. He, M. Khodri et al. "A major advance of tropical Andean glaciers during the Antarctic cold reversal." Nature 513 (2014): 224–228.
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Licht, A., M. van Cappelle, H. A. Abels, J. B. Ladant, J. Trabucho-Alexandre, C. France-Lanord, Y. Donnadieu, J. Vanderberghe, T. Rigaudier, C. Lécuyer et al. "Asian monsoons in a late Eocene greenhouse world." Nature 513 (2014): 501–506.
Résumé : The strong present-day Asian monsoons are thought to have originated between 25 and 22 million years (Myr) ago, driven by Tibetan–Himalayan uplift. However, the existence of older Asian monsoons and their response to enhanced greenhouse conditions such as those in theEocene period (55–34Myrago) are unknownbecause of the paucity of well-dated records. Here we show late Eocene climate records revealing marked monsoon-like patterns in rainfall and wind south and north of the Tibetan–Himalayan orogen. This is indicated by low oxygen isotope values with strong seasonality in gastropod shells and mammal teeth from Myanmar, and by aeolian dust deposition in northwest China. Our climate simulations support modern-like Eocene monsoonal rainfall and show that a reinforced hydrological cycle responding to enhancedgreenhouse conditions counterbalanced the negative effect of lowerTibetanrelief onprecipitation. These strong monsoons later weakened with the global shift to icehouse conditions 34Myr ago.
Mots-clés : cac
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Pasquini, L., J. F. Munoz, M. N. Pons, J. Yvon, X. Dauchy, X. France, Nang Dinh Le., C. France-Lanord, and T. Gömer. "Occurrence of eight household micropollutants in urban wastewater and their fate in a wastewater treatment plant. Statistical evaluation." Science of the Total Environment 481 (2014): 459–468.
Résumé : The occurrence in urban wastewater of eight micropollutants (erythromycin, ibuprofen, 4-nonylphenol (4-NP), ofloxacin, sucralose, triclosan, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS)) originating
from household activities and their fate in a biological wastewater treatment plant (WWTP) were investigated. Their concentrations were assessed in the liquid and solid phases (sewage particulate matter and wasted activated sludge (WAS)) by liquid chromatography–tandem mass spectrometry. The analysis of sewage from two different urban catchments connected to the WWTP showed a specific use of
ofloxacin in the mixed catchment due to the presence of a hospital, and higher concentrations of sucralose in the residential area.
The WWTP process removed over 90% of ibuprofen and triclosan from wastewater, while only 25% of ofloxacin was eliminated. Erythromycin, sucralose and PFOA were not removed from wastewater, the influent and effluent concentrations remaining at about 0.7 μg/L, 3 μg/L and 10 ng/L respectively. The behavior of PFOS and
4-nonylphenol was singular, as concentrations were higher at theWWTP outlet than at its inlet. This was probably related to the degradation of some of their precursors (such as alkylphenol ethoxylates and polyfluorinated compounds resulting in 4-NP and PFOS, respectively) during biological treatment.
4-NP, ofloxacin, triclosan and perfluorinated compounds were found adsorbed on WAS (from 5 ng/kg for PFOA to 1.0 mg/kg for triclosan). The statistical methods (principal component analysis and multiple linear regressions) were applied to examine relationships among the concentrations of micropollutants and macropollutants (COD, ammonium, turbidity) entering and leaving the WWTP. A strong relationship with ammonium indicated that some micropollutants enter wastewater via human urine. A statistical analysis of WWTP operation gave a model for estimating micropollutant output from the WWTP based on a measurement of macropollution parameters.
Mots-clés : cac
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Rollion-Bard, C., and D. Blamart. "SIMS method and examples of applications in coral biomineralization." In in : Biomineralization Handbook: Characterization of Biominerals and Biomimetic Materials, edited by Taylor & Francis Group CRC Press, 249–261. DiMasi, E.; Gower, L.B., 2014.
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2013 |
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Hindshaw, R. S., B. Bourdon, P. A. E. Pogge von Strandmann, N. Vigier, and K. W. Burton. "The stable calcium isotopic composition of rivers draining basaltic catchments in Iceland." Earth and Planetary Science Letters 374 (2013).
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Mabry, J., T. Lan, P. Burnard, and B. Marty. "High-precision helium isotope measurements in air." Journal of Analytical Atomic Spectrometry 28 (2013): 1903.
Résumé : Helium has two natural isotopes which have contrasted, and variable sources and sinks in the atmosphere (3He/4Heair ¼ 1.382 +- 0.005 x 10-6). Variations in the atmospheric helium isotopic composition may exist below typical measurement precision thresholds (0.2 to 0.5%, 2s). In order to investigate this possibility, it is necessary to be able to consistently measure helium isotopes in air with high precision (below 0.2% 2s). We have created an air purification and measurement system that improves the helium isotope measurement precision. By purifying a large quantity of air at the start of a measurement cycle we can
make rapid standard-bracketed measurements. Controlling the amount of helium in each measured aliquot minimizes pressure effects. With this method we improve the standard errors by 2 x over measuring the same amount of gas in a single step. Individual measurements have standard errors of 0.2 to 0.3% (2s), with three repeat samples needed to reach 0.1% or better errors. The long-term reproducibility of our calibration sample is 0.033% (2s).
Mots-clés : cac
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Animators : Pierre-Henri Blard & Albert Galy
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