Dissertationen zum Thema „Altération des silicates“
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Dubernet, Stéphan. „Défauts ponctuels dans les silicates : élaboration, coloration, altération de verres archéologiques, caractérisation de défauts dans un luminiphore silicaté“. Bordeaux 3, 1997. http://www.theses.fr/1997BOR30205.
Der volle Inhalt der QuelleGudbrandsson, Snorri. „Experimental weathering rates of aluminium-silicates“. Toulouse 3, 2013. http://thesesups.ups-tlse.fr/2225/.
Der volle Inhalt der QuelleThe chemical weathering of primary rocks and minerals in natural systems has a major impact on soil development and its composition. Chemical weathering is driven to a large extent by mineral dissolution. Through mineral dissolution, elements are released into groundwater and can readily react to precipitate secondary minerals such as clays, zeolites, and carbonates. Carbonates form from divalent cations (e. G. Ca, Fe and Mg) and CO2, and kaolin clay and gibbsite formation is attributed to the weathering of aluminium- rich minerals, most notably the feldspars. The CarbFix Project in Hellisheiði SW-Iceland aims to use natural weathering processes to form carbonate minerals by the re-injection of CO2 from a geothermal power plant back into surrounding basaltic rocks. This process is driven by the dissolution of basaltic rocks, rich in divalent cations, which can combine with injected CO2 to form and precipitate carbonates. This thesis focuses on the dissolution behaviour of Stapafell crystalline basalt, which consists of three major phases (plagioclase, pyroxene, and olivine) and is rich in divalent cations. Steady-state element release rates from crystalline basalt at far-from-equilibrium conditions were measured at pH from 2 to 11 and temperatures from 5° to 75° C in mixed-flow reactors. Steady-state Si and Ca release rates exhibit a U-shaped variation with pH, where rates decrease with increasing pH at acid condition but increase with increasing pH at alkaline conditions. Silicon release rates from crystalline basalt are comparable to Si release rates from basaltic glass of the same chemical composition at low pH and temperatures =25°C but slower at alkaline pH and temperatures =50°C. In contrast, Mg and Fe release rates decrease continuously with increasing pH at all temperatures. This behaviour is interpreted to stem from the contrasting dissolution behaviours of the three major minerals comprising the basalt: plagioclase, pyroxene, and olivine. Element release rates estimated from the sum of the volume fraction normalized dissolution rates of plagioclase, pyroxene, and olivine are within one order of magnitude of those measured in this study. In addition, these experimental results show that during injection of CO2-charged waters with pH close to 3. 6, crystalline basalt preferentially releases Mg and Fe relative to Ca to the fluid phase. The injection of acidic CO2-charged fluids into crystalline basaltic rocks may therefore favour the formation of Mg and Fe carbonates rather than calcite at acidic to neutral conditions. Plagioclase is the most abundant phase in crystalline basalts and thus influences strongly its reactivity. Plagioclase dissolution rates based on Si release show a common U-shaped behaviour as a function of pH where rates decrease with increasing pH at acid condition but increase with increasing pH at alkaline conditions. Constant pH plagioclase dissolution rates increase with increasing anorthite content at acid conditions, in agreement with literature findings. Interpretation and data fitting suggests that plagioclase dissolution rates are consistent with their control by the detachment of Si-rich activated complexes formed by the removal of Al from the mineral framework. Most notably, compared with previous assumptions, plagioclase dissolution rates are independent of plagioclase composition at alkaline conditions, e. G. Anorthite-rich plagioclase dissolution rates increase with increasing pH at alkaline conditions. At such conditions rapid plagioclase dissolution rates likely dominate divalent metal release from crystalline basalts to the fluids phase due to its high Ca content. Gibbsite is commonly the first mineral formed during low temperature dissolution of plagioclase. Gibbsite is an aluminium-hydroxide that is found in various soils as well as the dominant phase in many bauxite ores. Gibbsite precipitation rates were measured in closed system reactors at alkaline condition, both at 25 °C and 80 °C as a function of fluid saturation state. Analyses of the solids demonstrate that gibbsite precipitation occurred in all experiments. The comparison of gibbsite precipitation to the dissolution rates of plagioclase at pH 11 shows that the rates are close to equal. The precipitation rates of gibbsite, however, decrease faster with decreasing pH than plagioclase dissolution rates. As such it seem likely that plagioclase dissolution is faster than gibbsite precipitation at near to neutral pH, and the relatively slow rate of gibbsite precipitation influences plagioclase weathering in many Earth surface systems. Kaolinite is commonly the second secondary mineral formed during low temperature dissolution of plagioclase. Kaolinite precipitation rates were measured in mixed flow reactors as a function of fluid saturation state at pH=4 and 25 °C. In total eight long-term precipitation experiments were performed in fluids mildly supersaturated with respect to kaolinite, together with a known quantity of cleaned low defect Georgia Kaolinite as seeds. Measured kaolinite precipitation rates are relatively slow compared with plagioclase dissolution rates. This observation suggests that kaolinite formation during weathering is limited by its precipitation rates rather than by the availability of aqueous species sourced from plagioclase dissolution. Taken together the results of this study provide some of the fundamental scientific basic for predicting the rates and consequences of crystalline basalt and plagioclase dissolution at both the Earth's surface and during the near surface injection of CO2 as part of carbon storage efforts. Results indicate that although gibbsite precipitation rates are relatively rapid, the relatively slow precipitation rates of kaolinite may be the process controlling the formation of this mineral at the Earth's surface. This observation highlights the need to further quantify this secondary mineral precipitation rates at conditions typical at the Earth's surface. Moreover, as the composition of divalent metals released from crystalline basalts varies significantly with pH, CO2 carbonation in basalt should yield a systematic variation in the identity of carbonate and zeolite minerals precipitated with distance from the injection site. This latter conclusion can be tested directly as part of the currently on-going CarbFix project in Hellisheiði, Iceland
Aouad, Georges. „Influence de Pseudomonas aeruginosa sur la dégradation de silicates : Incidence sur la stabilité de matrices de confinement de déchets et d'un machefer industriel“. Université Louis Pasteur (Strasbourg) (1971-2008), 2006. https://publication-theses.unistra.fr/restreint/theses_doctorat/2006/AOUAD_Georges_2006.pdf.
Der volle Inhalt der QuelleToday it is generally accepted that alteration of rocks as well as anthropogenic products is not only driven by the interaction with water or mineral aqueous solutions. Organic compounds and also microorganisms are of importance for material degradation together with secondary mineralization. However, the exact role of some bacteria in these processes remains unclear in such complex systems. There is no convincing experimental validation of such phenomenon for silicate phases. The goal of this thesis was to experimentally evaluate the effect of one type of bacteria largely widespread in nature and producing biofilm (Pseudomonas aeruginosa) during the alteration of some silicates of environmental interest. The tested materials are the french nuclear glass SON68, a basaltic glass, a vitrified industrial bottom ash (JAP) and a municipal solid waste incinerator bottom ash (MIOM). We elaborated a specific medium allowing both the growth of Pseudomonas aeruginosa and a precise measurement of trace elements solubilized from materials. The total solubilized mass are systematically higher in sterile condition than in biotic one in proportions going from 26 to 79% depending on element and material. The dissolution rate of MIOM is 5. 3 10-4 g. M-2. J-1 in biotic condition and 7. 6 10-4 g. M-2. J-1 in the sterile one. The vitrified bottom ash dissolution rate is 7. 7 10-4 g. M-2. J-1 in presence of P. Aeruginosa and 12. 8 10-4 g. M-2. J-1 without bacteria. Basalt deteriorates with a rate of 18. 3 10-4 g. M-2. J-1 in biotic and 29. 8 10-4 g. M-2. J-1 in sterile system. Finally SON68 glass has a dissolution rate of 17. 6 10-4 g. M-2. J-1 in biotic medium and 25. 0 10-4 g. M-2. J-1 in the sterile one. In addition, the biofilm trap large proportions of potentially toxic elements
Rassineux, François. „Altération des mortiers : étude expérimentale et analogues anciens“. Poitiers, 1987. http://www.theses.fr/1987POIT2314.
Der volle Inhalt der QuelleSterpenich, Jérôme. „Altération des vitraux médiévaux : contribution à l'étude du comportement à long terme des verres de confinement“. Nancy 1, 1998. http://docnum.univ-lorraine.fr/public/SCD_T_1998_0211_STERPENICH.pdf.
Der volle Inhalt der QuelleMoquet, Jean-Sébastien. „Caractérisation des flux d'altération des contextes orogéniques en milieu tropical : cas des bassins andins et d'avant pays de l'Amazone“. Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1333/.
Der volle Inhalt der QuelleThe weathering flux estimation of orogenic belts and the identification of critical parameters that control these processes is a major question in the study of the long term carbon cycle. The objective of this research is to estimate the weathering of the Andean (the second largest orogenic belt after Himalaya) and foreland basins of the Amazon (the world's largest river) and to discuss variability according to geographical characteristics (climate, vegetation cover, lithology, erosion). The weathering fluxes of the Andean and foreland parts of the Amazon basin were estimated at high time and spatial resolution scales in the PHICAB, HIBAM and ORE-HYBAM frameworks. The Andean and foreland basins control the production of around 70% of the Amazon dissolved load. The carbonates and evaporites weathering in Marañón and Ucayali basins contribute approximately 70% of the total. The first order dissolved load spatial variability is controlled by the runoff and lithology (carbonates/silicates) variability. With the exception of the evaporites dissolution load products, the temporal variability of the dissolved load is firstly controlled by the hydrological variability. The silicate weathering variability in the Andean domain is not associated with the erosion rates variability. The dissolved rates are somewhat higher in the recent sedimentation areas (which correspond to Madeira subsidence foreland areas) than those calculated in foreland areas subjected to erosion if we normalize by the runoff (Napo). The atmospheric CO2 consumption derived from silicate weathering (CO2 sil) of the Andes and Foreland part represents 50-73% of the total CO2 sil budget of the Amazon. The Solimões plain contributes significantly to the Amazon basin CO2 sil. The Upper Amazon's silicate CO2 consumption flux is commensurate with the Himalaya's basins for an area two times lower and a runoff value two times higher. This result points out the importance of the climate for the CO2 sil consumption by tropical orogenic belts. 80% of the Amazon basin silicate weathering intensity is controlled by the runoff spatial variability, independently of the mobil cation content
Wild, Bastien. „Changements microstructuraux et diversité microbienne associés à l'altération des silicates : influence sur les cinétiques de dissolution du laboratoire au terrain“. Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAH004/document.
Der volle Inhalt der QuelleChemical weathering of silicate minerals is central to numerous environmental and societal challenges. This study addresses the long-standing question of the inconsistency between field and laboratory estimates of dissolution kinetics, by revisiting current approaches of mineral reactivity. It is demonstrated that evolution of feldspar reaction rates are inaccurately describedby current kinetics rate laws, due to textural and structural changes occurring at the fluid-mineral interface over the course of the dissolution process. A novel method is developed to enable probing biogeochemical weathering rates in the field. Bacterial and fungal metagenomic data reveal that subtle reciprocal relationships are established between microorganisms and mineral substrates within the mineralosphere. This thesis emphasizes the impact of passivation phenomena on dissolution rates, under field-relevant reacting conditions and the incapacity of microorganisms to overcome the passivation barrier
Hemadi, Hallouma. „Les silicates et carbonates authigènes de diapirs du Nord de la Tunisie : signification chimique et thermique“. Paris 11, 1987. http://www.theses.fr/1987PA112182.
Der volle Inhalt der QuelleRuan, Xiaobai. „Géochimie des rivières du bassin de Chayu (Sud-est du Tibet) et altération du batholithe du Trans-Himalaya“. Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0053.
Der volle Inhalt der QuelleThis thesis aims to understand better why and how the climate cooling, CO₂ drawdown and the marine Sr isotopic ratio increase all happened during Eocene/Oligocene. I checked the possibility of Trans-Himalaya weathering as the candidate for explaining the early change in marine ⁸⁷Sr/⁸⁶Sr and atmospheric CO₂ during Eocene/Oligocene, by studying the modern chemical weathering of the Trans-Himalaya batholith under monsoon climate. We choose the Chayu River Catchment locating in the SE Tibet as the study area for three reasons: 1) this catchment is mostly covered by the granitoid rocks of the Trans-Himalaya batholith, 2) it is now under the monsoon climate and 3) it is experiencing intense tectonic activity. Besides, the alpine part of the catchment is under periglacial environment, and there is a lack of knowledge about alpine periglacial weathering especially in active mountain ranges. Combining the above, we set two objects of the thesis: first, to study the periglacial weathering process in active alpine mountain of the Chayu Catchment, and second to study the weathering budget and the ⁸⁷Sr/⁸⁶Sr ratios of the catchment, in order to figure out the atmospheric CO₂ sinks and sources, the climatic dependency of chemical weathering rates and the Sr systematics of the Chayu Catchment. Samplings for the main river, tributaries and seepages of mass wasting deposits were conducted at the end of monsoon season in 2019. To study the alpine periglacial weathering processes, we compared the seepages from mass wasting deposits generated by freeze-thaw processes under periglacial environment and landslide under monsoon climate, and the nearby streams of these two climatic conditions. The landslide seepages under monsoon climate are more concentrated than nearby streams, and the seepages under periglacial environment are as concentrated as the landslide seepages but exhibit negligible differences than nearby streams. Our analyses on elemental ratios indicate that the freeze-thaw process provide an exposure mechanism similar to landslide to facilitate the weathering of reactive mineral phases of calcite, biotite and sulphide. The similarity between periglacial seepages and streams may indicate the widespread periglacial mass wasting deposits has a decisive influence on the river chemistry in alpine periglacial areas. To discuss the weathering budgets of the Chayu River Catchment, we first identified and corrected the river composition for the influences of secondary calcite precipitation (SCP). It is found that the weathering budget is dominated by carbonate weathering even though the lithology is mostly granitoid, and the degree of SCP is higher in the periglacial North Chayu than in the South Chayu, and is closely related to the carbonate weathering contribution. The δ¹³CDIC and sulphate proportion together tell that the chemical weathering of the Chayu catchment is mostly driven by carbonic acid, although sulphuric acid weathering is widespread. Combining the budgets of substrates and acids, the chemical weathering of the modern Chayu River Catchment is a CO₂ source rather than a CO₂ sink. After estimating the relative discharge of each tributary by δ¹⁸O of the river water, the carbonate and silicate weathering rates in each tributary basin are calculated. The carbonate weathering rates are basically irrelevant to climatic factors while the silicate weathering rates are positive correlated with basin MAT and runoff. The ⁸⁷Sr/⁸⁶Sr ratios of the main river is around 0.735, suggesting the impact from radiogenic carbonate. Combining the results, the silicate weathering of Trans-Himalaya might be more important than today during Eocene/Oligocene with warmer and wetter climate, and it is also possible that the weathering at that time was thus reversed to a CO₂ sink. The radiogenic Sr signals of the Chayu River suggest the weathering of Trans-Himalaya was capable of rising the marine ⁸⁷Sr/⁸⁶Sr before Himalayan exhumation
Galai, Leila. „Les mécanismes réactionnels régissant les interactions verre-fer en solution aqueuse“. Thesis, La Rochelle, 2021. http://www.theses.fr/2021LAROS029.
Der volle Inhalt der QuelleThe geological disposal of high-level waste (HLW) developed by ANDRA, in France, is based on a multi-layer concept. The vitrified radioactive waste is placed in a stainless-steel container itself placed in a carbon steel overpack and disposed in Callovo-Oxfordian (Cox) claystone. The proximity between iron, glass and groundwater should involve a chemical interaction between them which can impact the long-term behaviour of nuclear vitrified waste. Previous study on the glass-iron system in geological storage conditions have highlights the phenomenology linked to this interaction. Iron has been almost unanimously described as increasing the alteration of glass. However, in the experimental setups chosen, the simultaneous alteration of glass and iron makes it difficult to identify the mechanisms prevailing at the interface of each material. In this thesis, we have therefore chosen to decompose the real and complex Glass / Steel / Clay / Solution system into two model study systems in order to better characterize the different mechanisms at each interface. The first experiments were about the corrosion of iron powder in the presence of Si. These experiments have shown that an increase in [Si] promotes the formation of Fe silicates at the expense of Fe oxides, but without leading to an increase in the amount of corroded iron. Kinetic investigations revealed that a complex germination-growth mechanism is behind the formation of Fe silicates. A simplified kinetic model has also been proposed. Then, the experimental system has been complexified with iron corrosion experiments in the presence of CJ1 simple glass and ISG glass. These experiments have shown that the presence of iron certainly leads to the deterioration of the glass, but this increase is strongly limited by three main parameters : the glass composition, the iron flux associated with the corrosion kinetics of the metal and pH. The chosen simplification approach therefore made it possible to dissociate the effect of each parameter and to locate the effect of Si on the corrosion of iron, to dissociate the effect of iron from the effect of pH on alteration of the glass and above all to highlight the importance of parameters such as the iron flow and the initial composition of the glass on the effect that the iron will have on the deterioration of the glass
Beaulieu, Emilie. „Modélisation hydrogéochimique des grands bassins fluviaux : implications du réchauffement climatique“. Phd thesis, Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1408/.
Der volle Inhalt der QuelleThe chemical weathering of continental surfaces represents the one of carbon sinks at the Earth's surface which regulates the climate through feedback mechanism. The weathering intensity is controled by climate but also by lithology, vegetal cover, hydrology and presence of smectites and acids in soils. In this work, a study at global scale on grid cells highlighted that a CO2 concentration increase in the atmosphere would involve a decrease of evaportanspiration due to stomatal progressive closure, and a rise of soil acidity related to enhanced biospheric productivity. These changes would promote the silicates chemical weathering and as a result, would lead to CO2 consumption increase by 3% for 100 ppmv of CO2 concentration rise in the atmosphere. Then, the study on the one of the most important catchments located in arctic environment, the Mackenzie basin (Canada), showed the high sensitivity of chemical weathering to sulfuric acid production. Indeed, the Mackenzie mean CO2 consumption has decreased by 56%, taking account the pyrite presence in the catchment. In addition, the mean CO2 consumption of this basin could rise by 53% between today climate and a climatic scenario predicted for the end of century
Beaulieu, Emilie. „Modélisation hydrogéochimique des grands bassins fluviaux : implications du réchauffement climatique“. Phd thesis, Université Paul Sabatier - Toulouse III, 2011. http://tel.archives-ouvertes.fr/tel-00649185.
Der volle Inhalt der QuelleBastian, Luc. „Impact des variations de la mousson Africaine sur l’érosion chimique des silicates dans le bassin versant du Nil depuis 100.000 ans“. Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4101/document.
Der volle Inhalt der QuelleThis thesis presents a reconstruction of the chemical weathering in the Nile basin since 100.000 years. His objective is to better understand the impact of climatic variations on chemical weathering, to better. This work is based on the geochemistry study on marine core recorded in the Nile delta, on a time scale of 100.000 years. It use a novel approach with the coupling of à source tracer (εNd) and chemical weathering tracers (δ7Li and elementary ratios) on the fine fraction (< 2µm). In addition, it was analyzed samples of each actual Nil sources and a core sample from Tana Lack (Ethiopie). The results of this studies have enabled to reconstruct the chemical weathering variations in the Nile basin since 100.000 years. It show a rapid respond of chemical weathering to climate variations. This was also observed by important impact of North Atlantic climate variations on the decrease of chemical weathering in the Nile basin. At present, the chemical weathering flux and the CO2 consumption of the Ethiopian traps are low comparted to the other basaltic regions, as the Deccan. However, our results show that during the most humid periods (African Humid Period) the CO2 consumption was 2 to 3 time higher than today. This indicates that the Ethiopian traps could be have played a non-negligible role in the global CO2 cycle during the Cenozoic, and principally during the most humid periods in North Africa. Finally, analytical developments have been realized to be able to exploit the lithium isotopes on biogenic carbonates as a new tracer of Nile water flood. The results suggest an influence of “vital” effect and diagenetic process
Henchiri, Soufian. „Les isotopes du lithium, traceurs de la zone critique de la Terre : du local au global“. Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC201.
Der volle Inhalt der QuelleThe Critical Zone of the Earth is the layer covering its surface, at the interface between the water cycle, the lithosphere and the biosphere. This layer is produced at its base by chemical weathering and destroyed at its top by mechanical erosion. We explore the potential of lithium isotopes dissolved in rivers as tracers of continental chemical weathering processes as lithium and its isotopes are highly fractionated between the dissolved and solid phases during water-rock interaction processes. First, we are focused on the Congo Bassin. This study demonstrates the equivocal response of the isotopic composition of the riverine dissolved Li isotope compositions (δ7Li) to flat topography (and high weathering intensities). Two extreme values of dissolved δ7Li are produced in the Congo Basin, which trace two distinct continental weathering styles in which chemical weathering processes are different. On the other hand, we refined the mean flux of Li and its average isotopic signature exported to the ocean by rivers today (5.5×1010 g. an-1 et 19±2‰, respectively). We show that dissolved δ7Li in large rivers is controlled, at first-order, by the re-incorporation of Li into secondary weathering minerals (in soils and floodplains) and in, an equivocal way, of the weathering intensity. Moreover, the study of dissolved δ7Li in rivers draining volcanic islands (Iceland, Java, Martinique, Sao Miguel and Reunion) shows that continental hydrothermal activity, producing waters with high Li concentration with low value of δ7Li (as low fractionated towards the basaltic bedrock), influences the dissolved δ7Li in rivers of volcanic islands and can have an impact on the Li flux (and its δ7Li) transferred to the ocean on a global scale. Finally, by using a simple box model of the ocean and our results, we suggest an interpretation of the 9‰ increase of seawater δ7Li during the Cenozoic. This thesis highlights that riverine dissolved Li isotopes confirm once again their capacity to be powerful tracers of the weathering regimes of continental silicate rocks (even in anthropized context, as showed by our study of the Orgeval catchment, in Seine-et-Marne). Li and its isotopes are thus promising tracers of the Critical Zone of the Earth and the chemical weathering paleo-processes as well as the long-term geodynamic evolution of the continents or even the large vertical movements affecting the continental lithosphere
Mensi, Gabriel. „Etude pétrogénétique des occurrences alumineuses de l'unité 1 d'Avène (Montagne noire, Hérault)“. Phd thesis, Grenoble 1, 1988. http://tel.archives-ouvertes.fr/tel-00744051.
Der volle Inhalt der QuelleGavarini, Stéphane. „Durabilité chimique et comportement à l'irradiation des verres quaternaires LnYSiAlO (Ln = La ou Ce)“. Phd thesis, Université d'Orléans, 2002. http://tel.archives-ouvertes.fr/tel-00002852.
Der volle Inhalt der QuelleYan, Yongning. „Altération des sables par des solutions basiques“. Nancy 1, 1995. http://www.theses.fr/1995NAN10078.
Der volle Inhalt der QuelleMaffre, Pierre. „Interactions entre tectonique, érosion, altération des roches silicatées et climat à l'échelle des temps géologiques : rôle des chaînes de montagnes“. Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30287.
Der volle Inhalt der QuelleThis thesis explores how orogenies may affect the Earth climate through the quantification of the interactions between climate dynamics, continental erosion, silicate rock weathering rate and geological carbon cycle. The first chapter describes the mechanisms linking the continental topography and its impacts on the atmospheric and oceanic circulations, with emphasis on the thermohaline circulation. The second chapter compares the effects on continental weatherability of climate dynamics and erosional changes related to the presence of mountains. The third chapter describes a dynamic model of regolith designed for global scale simulations, and describes its transient behavior, as well as its response to a CO2 degassing. Finally, the last chapter presents a numerical model of the continental isotopic cycle of lithium, so that its reliability as a proxy of the past weathering can be tested. The model explores the case study of the Amazon lithium cycle
STERPENICH, Jérôme. „Altération des vitraux médiévaux. Contribution à l'étude du comportement à long terme des verres de confinement“. Phd thesis, Université Henri Poincaré - Nancy I, 1998. http://tel.archives-ouvertes.fr/tel-00007665.
Der volle Inhalt der QuelleOulkadi, Djihad. „Gels de silice hybrides dopés en particules colloïdales de smectites pour l'étude des interactions bactérie/silicate“. Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0064/document.
Der volle Inhalt der QuelleThis work deals with the study of bacteria/silicate interactions by using new hybrid materials, i.e. hybrid silica gel dopped with colloidal smectite particles (HSG). The aims are (1) to characterize HSG physicochemical properties and (2) to get a better knowledge about mineral/bacteria interactions. In a first part of the thesis, it is shown that HSG is a fractal silica network containing well-dispersed mineral particles. Hydrothermal treatment is necessary to stabilize the HSG structure. In the second part, it is shown that diffusion of organic acids and siderophores is sufficient to explain the high efficiency of bacterial action compared to abiotic treatments. Preventing bacterial adhesion or biofilm formation at the mineral surface permits to enhance the influence of metabolites diffusion. To conclude, the advantages and limits of using HSG in environmental studies are discussed
Robinet, Laurianne. „The role of organic pollutants in the alteration of historic soda silicate glasses“. Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/1475.
Der volle Inhalt der QuelleDavenport, Jesse. „Isotopic tracing of silicate and carbonate weathering in the Himalayan erosional system“. Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0241.
Der volle Inhalt der QuelleWeathering of Himalayan lithologies has had a potential impact on the global carbon cycle. To be able to constrain and understand the processes that occurred in the Himalayas that affected these cycles, we must be able to distinguish the signatures of silicate and carbonate weathering in the dissolved load of Himalayan rivers. Previous studies have attempted to do this using a variety of methods but there is still not a clear consensus on the magnitude and flux of silicate weathering in the Himalaya. This thesis proposes the use of 40Ca as a tracer that could improve the quantification of the silicate and carbonate weathering flux in the dissolved load of Himalayan rivers. Previous work has shown that the 40Ca budget of seawater is dominated by a mantle source, such that marine carbonates have a homogeneous 40Ca signature indistinguishable from the mantle value. In contrast, the upper silicate crust is expected to have developed a radiogenic composition. The difference between the radiogenic Ca signature of carbonate and silicate lithologies can be therefore used to differentiate between carbonate and silicate weathering in the dissolved load of rivers. Here, we present a geochemical survey, including radiogenic Ca analyses, of rivers draining the main lithological units of the Himalaya, as well as results from sediments, bedrock, soil and gravel. Our results show that Himalayan carbonates exhibit no radiogenic 40Ca excesses despite highly variable 87Sr/86Sr signatures, whereas sediments are variably radiogenic (+0.9 to +4). This suggests that for Ca, unlike for Sr, isotopic exchange between the silicate and carbonate lithologies has been minimal. The radiogenic Ca composition of river water ranges from +0.1 in carbonate dominated catchments to +11 in rivers draining silicate catchments. For large rivers, silicate and carbonate weathering budget estimates based on major elements and radiogenic Ca compositions tend to agree. However, for some smaller rivers, especially those draining silicate dominated basins in the HHC and LH formations, some discrepancies are observed. These cannot be attributed to poor definition of the chemical or radiogenic Ca composition of the endmembers used for budget modeling, as the values required to bring the estimates into agreement are unreasonable. They also cannot be explained by precipitation of secondary carbonates in the rivers as the non-radiogenic composition of the carbonate fraction of sediments suggests that this process is only minor. Rather, these discrepancies may be due to the dissolution/weathering of trace amounts of radiogenic calcite contained within HHC and LH silicate lithologies. The weathering of such material, which represents only a tiny fraction of the area of the silicate catchment, could yield a substantial proportion of the radiogenic Ca and may thus have a significant influence on the isotopically based weathering budgets of these basins. Nevertheless, as this effect is observed primarily in basins with low silicate erosion rates, its influence on estimates of the overall silicate weathering flux will be minor. More generally, the results of this thesis imply that the 40K–40Ca system can resolve issues that cannot be successfully addressed using Sr isotopes in the Himalaya. Further work is needed to define the full range of radiogenic Ca compositions in the Himalaya in order to clearly answer questions regarding silicate weathering fluxes
Pollet-Villard, Marion. „Évolution de la surface réactive du feldspath potassique au cours de son altération en contexte géothermal : étude expérimentale et modélisation“. Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAH015/document.
Der volle Inhalt der QuelleThis thesis aims at quantifying the reactive surface area evolution of dissolving K- feldspar, and evaluating the impact on the dissolution kinetics during its alteration in geothermal context. The study focuses on : (1) the influence of secondary coatings on the orthoclase surface, (2) the impact of the anisotropic crystalline structure of orthoclase and (3) the effect of etch pit formation on the mineral surface. Experimental and numerical results highlight that the orthoclase dissolution rate and its evolution over time mainly depends onits morphology. Some orthoclase faces dissolve 10 times faster than others, resulting in an increase of the surface proportion of rapid vs. slow dissolving faces during the process and the increase of up to an order of magnitude of the overall orthoclase dissolution rate. These results question the significance of rate laws and reaction mechanisms determined from powder experiments and the pave to new approaches for investigating mineral reactivity
Dudoignon, Patrick. „Les altérations hydrothermales des roches volcaniques de l'atoll de Mururoa (Polynésie française)“. Poitiers, 1988. http://www.theses.fr/1988POIT2007.
Der volle Inhalt der QuelleDavenport, Jesse. „Isotopic tracing of silicate and carbonate weathering in the Himalayan erosional system“. Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0241.
Der volle Inhalt der QuelleWeathering of Himalayan lithologies has had a potential impact on the global carbon cycle. To be able to constrain and understand the processes that occurred in the Himalayas that affected these cycles, we must be able to distinguish the signatures of silicate and carbonate weathering in the dissolved load of Himalayan rivers. Previous studies have attempted to do this using a variety of methods but there is still not a clear consensus on the magnitude and flux of silicate weathering in the Himalaya. This thesis proposes the use of 40Ca as a tracer that could improve the quantification of the silicate and carbonate weathering flux in the dissolved load of Himalayan rivers. Previous work has shown that the 40Ca budget of seawater is dominated by a mantle source, such that marine carbonates have a homogeneous 40Ca signature indistinguishable from the mantle value. In contrast, the upper silicate crust is expected to have developed a radiogenic composition. The difference between the radiogenic Ca signature of carbonate and silicate lithologies can be therefore used to differentiate between carbonate and silicate weathering in the dissolved load of rivers. Here, we present a geochemical survey, including radiogenic Ca analyses, of rivers draining the main lithological units of the Himalaya, as well as results from sediments, bedrock, soil and gravel. Our results show that Himalayan carbonates exhibit no radiogenic 40Ca excesses despite highly variable 87Sr/86Sr signatures, whereas sediments are variably radiogenic (+0.9 to +4). This suggests that for Ca, unlike for Sr, isotopic exchange between the silicate and carbonate lithologies has been minimal. The radiogenic Ca composition of river water ranges from +0.1 in carbonate dominated catchments to +11 in rivers draining silicate catchments. For large rivers, silicate and carbonate weathering budget estimates based on major elements and radiogenic Ca compositions tend to agree. However, for some smaller rivers, especially those draining silicate dominated basins in the HHC and LH formations, some discrepancies are observed. These cannot be attributed to poor definition of the chemical or radiogenic Ca composition of the endmembers used for budget modeling, as the values required to bring the estimates into agreement are unreasonable. They also cannot be explained by precipitation of secondary carbonates in the rivers as the non-radiogenic composition of the carbonate fraction of sediments suggests that this process is only minor. Rather, these discrepancies may be due to the dissolution/weathering of trace amounts of radiogenic calcite contained within HHC and LH silicate lithologies. The weathering of such material, which represents only a tiny fraction of the area of the silicate catchment, could yield a substantial proportion of the radiogenic Ca and may thus have a significant influence on the isotopically based weathering budgets of these basins. Nevertheless, as this effect is observed primarily in basins with low silicate erosion rates, its influence on estimates of the overall silicate weathering flux will be minor. More generally, the results of this thesis imply that the 40K–40Ca system can resolve issues that cannot be successfully addressed using Sr isotopes in the Himalaya. Further work is needed to define the full range of radiogenic Ca compositions in the Himalaya in order to clearly answer questions regarding silicate weathering fluxes
Aubert, Dominique. „Contribution de l'altération et des apports atmosphériques aux transferts de matières en milieu silicaté : traçage par le strontium et les terres rares : cas du bassin versant du Strengbach (Vosges,France)“. Université Louis Pasteur (Strasbourg) (1971-2008), 2001. http://www.theses.fr/2001STR13202.
Der volle Inhalt der QuelleIn silicate catchments, weathering and exchange processes in soils and bedrock contribute to neutralize acid atmospheric inputs by the way of base cation release in drainage waters. In this study, we combined several geochemical tracers (like Sr isotopes and rare earth elements) to describe precisely the mechanisms controlling the weathering processes, which greatly influence the fluxes of chemical elements transported in surface waters. For the first time in the Strengbach experimental catchment, the annual atmospheric input of Sr has been quantified. We also demonstrated that REE in atmospheric solutions and lichens have a natural origin like terrigeneous particles (loess) but could also originate from anthropic inputs, particularly from the fertilizers. Compared to the deep soil horizons, the shallow soil horizons are MREE and HREE depleted. The selective dissolution of MREE and HREE-rich minerals like apatite mostly contribute to the mobilization of these elements in the soils. On the opposite, dissolved and suspended matter in the drainage waters show HREE enrichment. Moreover, Sr and Nd isotope show the strong influence of apatite and plagioclase dissolution on the isotopic composition of dissolved and particulate phases of the surface waters. A specific Sr isotopes study in the Strengbach streamwaters show that the variations of 87Sr/86Sr ratios are related to discharge variations. In this respect, we demonstrated that three different contributive areas influence the Sr concentrations and the Sr isotopic ratios in streamwaters depending on hydrological conditions prevailing in the catchment
Merceron, Thierry. „Les altérations hydrothermales de la coupole granitique d'échassières et de son environnement (sondage gpf echa n1)“. Poitiers, 1988. http://www.theses.fr/1988POIT2330.
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