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Maggie Cusack Yannicke Dauphin Jean-Pierre Cuif Murielle Salom Andy Freer Huabing Yin 《Chemical Geology》2008,253(3-4):172-179
Biominerals are natural composite materials comprising organic and inorganic components. Detailed knowledge of the nature and distribution of both components is a crucial requirement in order to advance our understanding of biomineral formation, their material properties and preservation potential as well as the interpretation of environmental data. Detailed chemical data are essential for our understanding of the nature and distribution of such components. Micro-XANES mapping at the sulphur K-edge reveals that, in the brachiopod Terebratulina retusa, the sulphate concentration is higher in the outer (primary) layer than in the calcite fibres of the secondary layer. This is co-incident with a higher magnesium concentration. In contrast, the sheaths surrounding the calcite fibres contain sulphur as thiol, confirming the presence of protein while, the sulphur within the fibres themselves, occurs as sulphate. Micro-XANES analysis of the insoluble organic extract from T. retusa indicates the presence of organic sulphate while Micro-Raman spectroscopy confirms that structurally substituted sulphate (SSS) is also present although semi-quantitative Raman spectroscopy carried out in this spectral region (wavenumbers 900–1200) indicates that the sulphate present is at the threshold of detection by Raman spectroscopy. The distribution of phosphorus in the shell of T. retusa correlates well with that of protein indicating the presence of phosphorylated proteins in the periostracum, the sheaths surrounding the calcite fibres and the interface between the primary and secondary layer. 相似文献
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The presence and localization of organic sulfate within coral skeletons are studied by using X-ray absorption near edge structure spectroscopy (XANES) fluorescence. XANES spectra are recorded from four reference sulfur-bearing organic molecules: three amino acids (H-S-C bonds in cysteine; C-S-C bonds in methionine; one disulfide bond C-S-S-C bonds in cystine) and a sulfated sugar (C-SO4 bonds in chondroitin sulfate). Spectral responses of three coral skeletons show that the sulfated form is extremely dominant in coral aragonite, and practically exclusive within both centres of calcification and the surrounding fibrous tissues of coral septa. Mapping of S-sulfate concentrations in centres and fibres gives us direct evidence of high concentration of organic sulfate in centres of calcification. Additionally, a banding pattern of S-sulfate is visible in fibrous part of the coral septa, evidencing a biochemical zonation that corresponds to the step-by-step growth of fibres. 相似文献
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Murielle Perronnet Frédéric Villiéras Michel Jullien Joël Raynal 《Geochimica et cosmochimica acta》2007,71(6):1463-1479
In the context of the potential confinement of high-level radioactive wastes (HLW) within the clay engineered barrier system (EBS) in deep geological formations, the evolution of the retention properties of smectite when interacting with Fe(0) needs to be assessed. If some potential natural analogues describing iron-clay reactivity are easily found, metallic iron-clay interactions are poorly described in studies regarding the Earth. Therefore, experimental investigations are needed. Several parameters influence Fe(0)-clay interactions, such as temperature, the interlayer composition of swelling clays, and the presence of octahedral Fe3+, etc. From a geometrical point of view, it is thought that clay destabilization is mainly controlled by phenomena starting at the edge faces of the particles. In the present work, the rates of the smectite-Fe(0) reaction at 80 °C were assessed by XRD, Mössbauer, and CEC analyses for three smectites. The investigations show marked differences in the degree of stability, which cannot be explained by the crystal-chemistry rules established in previous studies. Therefore, the Fe(0)-smectite interactions were studied in view of textural and energetic surface quantitative analyses. The studied smectites have equivalent nitrogen BET-specific surface areas, equivalent argon edge surface areas and slightly different basal surface areas. This similarity in particle shape indicates that the edge surface area cannot be accounted for when explaining the observed differences in reactivity. However, a correlation is obtained between smectite reactivity and the energetic heterogeneity of its edge faces. This is interpreted in terms of a multiplication of the number of sites on the edge faces, where the electron transfer between Fe(0) and the smectite structure can occur. 相似文献
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Julien Foriel Pascal Philippot Paul Dumas Murielle Salomé Bénédicte Ménez David Moreira 《Geochimica et cosmochimica acta》2004,68(7):1561-1569
Owing to the delicate nature of fossil microorganisms and inherent difficulties for discriminating true fossils from artifacts, an important challenge is to extract unequivocal biogenic information from individual microfossils using high-resolution, nondestructive and sensitive techniques. Here, we use combined synchrotron (X-ray microfluorescence, X-ray absorption near-edge structure and infrared microspectroscopies) and particle-induced X-ray emission analyses to image the spatial distribution at a μm-scale of a variety of potential biogenic markers (major and trace elements, C-H bonds, and sulfur-oxidation states) in individual prokaryotic microfossils. In particular, we analyzed iron-oxide fossil filaments of putative biogenic origin encapsulated with amorphous silica from a fragment of an inactive hydrothermal chimney of the East Pacific Rise. In order to test the biogenic origin of the markers studied, we performed the same analyses on filamentous bacteria corresponding most likely to the ?-Proteobacteria, and collected from substrates exposed to a hydrothermal fluid vent at the Mid-Atlantic Ridge. In both types of fossil and contemporary filaments, the occurrence of CH2 groups and of three sulfur species (sulfate, sulfite, organic S) showing heterogeneous distribution that underline the cytoplasm of individual cells in the case of the present-day filament, suggests that the original microorganisms were actively metabolizing sulfur. These results show the large potential of combining high-resolution synchrotron techniques to analyze individual microfossils for extracting unequivocal biogenic information. Furthermore, they also suggest that cooccurrence of different sulfur oxidation states within single microfossils could constitute a biogenic metabolic marker indicating S-metabolizing activities. 相似文献
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For ages, links between environment, climate and their impacts on human health have been observed and studied. Research to improve our understanding of environmental key determinants of infectious diseases can provide innovative information for adaptation strategies and lead to new tools optimizing surveillance, vector control measures, and disease prevention. As earth observation satellites can measure meteorological and environmental parameters, NASA and CNES have separately engaged in an innovative use of their earth observation infrastructure development programs: space tools addressing public health. As NASA and CNES have fruitful cooperation for satellite development missions for years, both health programs have proposed to explore a new area of collaboration: satellites addressing health issues. As members of international organizations, NASA and CNES could promote their common views towards the Group on Earth Observations (GEO) Community of Practice for Health & Environment and the Committee on Earth Observation Satellites (CEOS) Societal Benefit Area on Health. 相似文献
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Murielle Meurisse Brigitte Van Vliet-Lanoë Brigitte Talon Philippe Recourt 《Comptes Rendus Geoscience》2005,337(7):675-684
This survey of the coastal dunes of northern France is based on stratigraphy, 14C dating, sedimentology and morphology applied for palaeoclimatic and palaeodynamic purpose. The dunes rest on a Flandrian prism sealed by Atlantic peats grown backward from a subboreal dune ridge. Two historical building phases are recorded: the late Roman dunes and the 13th century dunes. These events are separated by pedogenesis. Contribution of reworked fluvial sands also records the recent climatic degradation, with an increased storminess (Little Ice Age) associated with more efficient erosion (soil erosion and floods). The dunes of Picardy also record the Global Warming: their morphologies attest a shift from parabolic into longitudinal, by coupling storminess and sea-level rise. To cite this article: M. Meurisse et al., C. R. Geoscience 337 (2005). 相似文献
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