Dissertationen zum Thema „Isotopes du Soufre et du Calcium“
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Jouini, Arbia. „Perturbations biogéochimiques à la limite Crétacé-Paléogène : apport des isotopes du Soufre et du Calcium“. Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0065.
Der volle Inhalt der QuelleThe Cretaceous-Paleogene boundary (KPg, -66 Ma) is associated to one of the deepest biogeochemical cycle disruptions in Earth's recent history. The events associated to the KPg boundary include one of the strongest known oceanic calcareous bioproduction crisis and are coeval with a bolid impact (that formed the Chixculub crater) and the emplacement of a Large Igneous Province (Deccan traps). Many studies investigated the mechanism(s) triggering the environmental perturbations and many questions remain unanswered regarding the relative contribution of the volcanic event and the impact on the KPg crisis. Yet, modification of the ocean-atmosphere system composition through massive input of sulfuric and carbonic acid very likely played a key, underconstrained, role.During this thesis project, I conducted high-resolution stable sulphur and calcium isotope records across the Cretaceous-Paleogene transition. These records are based on monospecific samples of planktonic and benthic foraminifera from the equatorial Pacific.The benthic and planktonic δ44/40Ca records before and after the K-Pg boundary allowed us to demonstrate a succession of episodes of ocean alkalinity change related to the increase in continental weathering and the biocalcification crisis caused by CO2 emissions from Deccan volcanism. Carbonate compensation through dissolution of carbonate sediments, reduction of biocalcification and/or increase in continental weathering had to occur to compensate for the excess CO2. As a result, this led to rapid changes in oceanic carbonate chemistry, in combination with a reduction in the export of surface alkalinity in response to the early Paleogene planktonic biomineralisation crisisExamination of sulphur cycle disruption instead supports the idea that mass extinction through the K-Pg transition is not associated with a global expansion of anoxic conditions, in contrast to the various Phanerozoic mass extinction events, where there are multiples evidences for the development of anoxic conditions associated with carbon cycle disruption. These findings are consistent with micropalaeontological observations that show no benthic foraminiferal mass extinction.This multi-proxy geochemical approach has the advantage of allowing a more detailed assessment of key parameters such as carbonate chemistry and oceanic anoxia across the Cretaceous-Paleogene transition, thus providing a clearer global picture of biogeochemical perturbations around this time
Labidi, Jabrane. „Origine, dynamique et multi-compositions isotopiques du soufre dans le manteau terrestre“. Paris 7, 2012. http://www.theses.fr/2012PA077165.
Der volle Inhalt der QuelleSulfur content and isotope composition of the terrestrial mantle can provide major constraints on the internal dynamic of this element and on nature of mantle heterogeneities. The mean S isotope composition of this reservoir can also characterize the potentiel mantle-core equilibrium and hence help to decipher the question of sulfur origin on Earth. In this study, we report S content and relative abundances of 32S, 33S, 34S and 36S in more than 120 glassy basalts coming from 3 ocean ridges and a transform fault. We propose a new sulfur extraction protocol for silicate glasses based on hydrofluoric acid. We evidenced an analytical bias affecting the previously published dataset, probably due to the use of the e"Kiba reagent". The redetermined δ34S are approximately 1‰ lower than the previously published data. We also provide the first Δ33S and Δ36S data for ocean ridge basalts. These date are, within uncertainty, indistinguishable from our CDT estimate, confirming the idea that terrestrial mantle has a Δ33S and Δ36S close to 0. 000‰ with respect to this international standard. The δ34S variability encompasses a 3‰ range in ocean ridge basalts and correlations between O34S and radiogenic isotopes demonstrate that S isotopes are tracers of mantle heterogeneities. On the other hand, the mean δ34S of MORB mantle is -0,80 ± 0,38‰, significantly lower than the chondritic value of 0,04 ± 0,31‰. The Pb-S isotope systematic in Pacific Antarctic basalts indicates that recycled oceanic crust bears a positive δ34S. As a corrollary, this result implies that the depleted part of the mantle is even more negative thant the mean MORB value. We propose a δ34S value of -1,40 ± 0,20‰ for this reservoir. In South Atlantic basalts, the δ34S are correlated with Sr isotopes, trends being consistent with recycled sediment feeding the mantle source of these basalts. Taken together, the δ34S variability associated to the Δ33S and Δ36S constancy indicates that the recycled components are a post-archean age, in agreement with independant estimation of their mean age using Pb isotopes. Finally, the negative δ34S of MORB mantle can be reconcilied only with a mantle-core equilibrium, implying an internal origin of sulfur as opposed to a late origin
Valdes, Maria. „Geochemistry and Cosmochemistry of Calcium Stable Isotopes“. Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/276866.
Der volle Inhalt der QuelleDoctorat en Sciences
info:eu-repo/semantics/nonPublished
Schmitt, Anne-Désirée. „Les isotopes du calcium : Développements analytiques.Application au bilan océanique présent et passé“. Université Louis Pasteur (Strasbourg) (1971-2008), 2003. http://www.theses.fr/2003STR13077.
Der volle Inhalt der QuelleFirst, a measurement protocol was developed at the Centre de Géochimie de la Surface to avoid instrumental fractionation. After chemical separation on ion exchanging resins, the Ca isotopic compositions were measured on a thermo-ionisation mass spectrometer, using a double-spike technique. The Ca isotopic ratios were expressed in a delta notation. To do this, a reference material is needed. No international standard presently exists for Ca isotopes. For that reason, we proposed to use the SRM 915a carbonaceous standard from the NIST. Seawater, the only common sample of most of previous studies has also been used: it was calibrated against the carbonaceous standard and used in present study. This protocol was then applied to study the Ca oceanic budget. The isotope data of continental waters allowed to constrain the Ca flux to the ocean. A limited variability of d44Ca (0. 5 ) was recorded at the outlet of main rivers or for hydrothermal vents. Moreover, no relationship was observed between d44Ca and the lithology or the climate of the studied watersheds. This allowed to determine the mean Ca isotopic composition of the Ca flux to the ocean (-1. 1 ± 0. 2 ) and to suggest that this value remains rather constant through time. A consequence of this value is that present-day seawater is at steady-state with regard to Ca isotopes. The d44Ca study of marine phosphates from Miocene and Pleistocene, which reflect the paleo-seawater variations through time, has shown that this was not necessarily the case in the past. At 22 Ma, a deviation in d44Ca through more positive values suggests that the intensity of the incoming and outcoming fluxes changed, but not their isotopic composition
Méhay, Sabine. „Etude de pétroles biodégradés : L'isotopie du soufre comme outil de corrélation et marqueur de processus d'altération“. Université Louis Pasteur (Strasbourg) (1971-2008), 2006. https://publication-theses.unistra.fr/public/theses_doctorat/2006/MEHAY_Sabine_2006.pdf.
Der volle Inhalt der QuelleIn the present study, the biodegradation of petroleum in reservoirs has been investigated by the molecular and isotopic study of three series of petroleum and core extracts, coming from Alberta (Canada), from the Potiguar Basin (Brazil) and from the San Joaquim Valley (California, USA). The molecular study allowed us to rank them according to the biodegradation scale of Peters and Moldowan (1993). This study also showed variations in the level of maturity reached by the samples and in the origin of the organic matter, within each series. However, correlations between oil samples as well as the identification of their source rocks appeared difficult to establish, due to the biodegradation of biomarkers. The sulfur isotopic study of oil samples showed that the 34S constitutes a good correlation tool because it does not seem to be affected by the biodegradation of sulfur organic compounds. However, this work suggested that secondary reactions of sulfur exchange and/or incorporation could happen with increasing biodegradation, and lead to variations in the sulfur isotopic composition of oil, in reservoirs containing H2S, generated notably by bacterial sulphate reduction. This was further corroborated by laboratory experiments of simulation. Finally, tests for the development of irm-GC/MS to measure the sulfur isotopic composition of individual compounds were performed in order to progress in the study of the sulfurization processes of organic matter
Baroni, Mélanie. „Etude des anomalies isotopiques du soufre et de l'oxygène dans le sulfate d'origine volcanique enregistré dans les archives glaciaires“. Université Joseph Fourier (Grenoble), 2006. http://www.theses.fr/2006GRE10121.
Der volle Inhalt der QuellePlinian volcanism modify climate for several years by injecting large quantities of sulfur dioxide directly into the stratosphere, further oxidized to sulfuric acid droplets which reflect solar radiations and change the radiative properties of the atmosphere. Up to now, the study of volcanic signals preserved in glaciological archives was limited to the measurements of sulfate concentrations. We propose the use of new tools which are the sulfur and oxygen isotopic anomalies of volcanic sulfate recorded in Dome C and South Pole, to provide further insights into past volcanism. A study of the temporal evolution of the sulfur and oxygen isotopic anomalies in the Agung (March 1963) and the Pinatubo (June 1991) volcanic sulfate, has been conducted. The sulfur isotopic anomaly changes in sign with time from an initial positive component to a negative value. This change in sign is accompanied by a significant depletion of heavy isotopes with time. Sulfur isotopic anomaly is created during sulfur dioxide photochemical oxidation to sulfuric acid on a month time scale, indicative of a fast process. The oxygen isotopic anomaly seems to be linked to the quasi-biennal oscillation of the stratosphere. Twelve volcanic eruptions have been studied over the last millenium, by taking the whole sulfate signal. Sulfur isotopic anomaly allowed the identification of 6 stratospheric volcanic eruptions revealing the power of this tool when the nature of the eruption is unknown
Kitayama, Yumi. „Les quatre isotopes du soufre dans les kimberlites de Sibérie, traceurs du recyclage de croûte océanique et de sédiments Archéens dans le manteau terrestre“. Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0244.
Der volle Inhalt der QuelleInherited from the early atmosphere, anomalies in the relative abundances of sulfur isotopes (32S, 33S, 34S and 36S) are recorded in sediments older than 2.5 billion year (i.e. Archean). Here we test the robustness of sulfur isotopes to trace the early recycling of oceanic crust and sediments that may have been transferred to the deep mantle or stored in the lithospheric mantle since the onset of subduction. In Siberia, the lithospheric mantle has been naturally sampled by the Udachnaya-East kimberlite while it was erupting. Because it is extremely well preserved, rich in Na, K, Cl, S and contains remnants of oceanic crust recycled during the Archean, this kimberlite enables us to test : (1) the hypothesis of an early recycling of Archean atmospheric sulfur in the lithospheric mantle and/or the deeper source of the kimberlite; (2) the coherence between in situ (SIMS in sulfide minerals) and bulk methods (chemical extraction of sulfur from powdered rocks, followed by gas source mass-spectrometry) for measuring multiple sulfur isotopes. Our results, combined with measurements of Rb-Sr, Sm-Nd and lead (204Pb, 206Pb, 207Pb, 208Pb) isotopes, show that: (1) sulfates from the Udachnaya-East kimberlite and its nodules composed of chloride-carbonate have a deep, magmatic origin, uncontaminated by host sediments, suggesting the presence of sulfate-rich, oxidized domains in the mantle; (2) measurements of sulfur isotopes by bulk methods are consistent with the sulfide populations observed in situ; (3) sulfides from salty kimberlites are depleted in 34S with respect to the chondritic value and record small anomalies in sulfur isotopes ; (4) sheared peridotites contain another population of sulfides that are depleted in 34S and preserve 33S and 36S anomalies inherited from the Archean surface, despite resetting of the U-Pb chronometer during kimberlite eruption
Kitayama, Yumi. „Les quatre isotopes du soufre dans les kimberlites de Sibérie, traceurs du recyclage de croûte océanique et de sédiments Archéens dans le manteau terrestre“. Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0244.
Der volle Inhalt der QuelleInherited from the early atmosphere, anomalies in the relative abundances of sulfur isotopes (32S, 33S, 34S and 36S) are recorded in sediments older than 2.5 billion year (i.e. Archean). Here we test the robustness of sulfur isotopes to trace the early recycling of oceanic crust and sediments that may have been transferred to the deep mantle or stored in the lithospheric mantle since the onset of subduction. In Siberia, the lithospheric mantle has been naturally sampled by the Udachnaya-East kimberlite while it was erupting. Because it is extremely well preserved, rich in Na, K, Cl, S and contains remnants of oceanic crust recycled during the Archean, this kimberlite enables us to test : (1) the hypothesis of an early recycling of Archean atmospheric sulfur in the lithospheric mantle and/or the deeper source of the kimberlite; (2) the coherence between in situ (SIMS in sulfide minerals) and bulk methods (chemical extraction of sulfur from powdered rocks, followed by gas source mass-spectrometry) for measuring multiple sulfur isotopes. Our results, combined with measurements of Rb-Sr, Sm-Nd and lead (204Pb, 206Pb, 207Pb, 208Pb) isotopes, show that: (1) sulfates from the Udachnaya-East kimberlite and its nodules composed of chloride-carbonate have a deep, magmatic origin, uncontaminated by host sediments, suggesting the presence of sulfate-rich, oxidized domains in the mantle; (2) measurements of sulfur isotopes by bulk methods are consistent with the sulfide populations observed in situ; (3) sulfides from salty kimberlites are depleted in 34S with respect to the chondritic value and record small anomalies in sulfur isotopes ; (4) sheared peridotites contain another population of sulfides that are depleted in 34S and preserve 33S and 36S anomalies inherited from the Archean surface, despite resetting of the U-Pb chronometer during kimberlite eruption
Cobert, Florian. „Processus et mécanismes physico-chimiques et biologiques responsables du fractionnement des isotopes du calcium“. Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00762532.
Der volle Inhalt der QuelleBoucher, Agnès. „Solubilisation et transfert des fertilisants et des phytosanitaires soufrés dans la zone non saturée sous le vignoble champenois : approche chimique et isotopique“. Reims, 2002. http://www.theses.fr/2002REIMS019.
Der volle Inhalt der QuelleTreatments of vines in Champagne contaminate solute of the unsaturated zone. This work aims at identifying the origins and fate of degradation products derived from fertilizers and pesticides, using time variations of sulfates concentrations vertical profiles and determination of d18O and d34S under different parcels. D34S of the main source of sulfur (fertilizers, elementary sulfur, pyrites) are well distinguished. The fertilizers and pesticides solubilization don't lead to an isotopic fractionation between the source compound and the derived sulfate. Moreover, sulfates don't interact with chalk. Sulfates indicate the advance of fertilizers and pesticides degradation products. They migrate according a convection/diffusion flow
Schmitt, Anne-Désirée. „Les isotopes du Calcium: Développements analytiques. Application au bilan océanique présent et passé“. Phd thesis, Université Louis Pasteur - Strasbourg I, 2003. http://tel.archives-ouvertes.fr/tel-00376191.
Der volle Inhalt der QuelleUn protocole de mesure permettant de s'affranchir du fractionnement instrumental a tout d'abord été développé au Centre de Géochimie de la Surface. Après séparation chimique sur résine échangeuse d'ions, les compositions isotopiques en Ca ont été déterminées au spectromètre de masse à thermo-ionisation par une technique employant un double spike. L'expression des rapports isotopiques du Ca sous forme de delta requiert l'emploi d'un matériel de référence. Aucun standard international n'existant pour les isotopes du Ca, le standard carbonaté SRM 915a du NIST a été proposé. L'eau de mer, seul échantillon commun à la majorité des études antérieures, a été calibré en fonction de ce standard carbonaté et utilisé pour ce travail.
Ce protocole a ensuite été appliqué à l'étude du bilan océanique du Ca. L'étude d'eaux continentales a permis de contraindre le flux de Ca arrivant aux océans. Il en résulte une variabilité limitée de δ44Ca (0,5 ‰) à l'embouchure des grands fleuves et pour les eaux hydrothermales. Aucune relation n'a en outre été observée entre δ44Ca et la lithologie ou le climat des bassins versants étudiés. Ceci a permis de calculer une composition isotopique moyenne en Ca arrivant aux océans égale à -1,1 ± 0,2 ‰ et de suggérer sa constance au cours du temps. Il résulte de cette valeur que l'océan actuel est à l'état stationnaire par rapport aux isotopes du calcium. L'étude du δ44Ca de phosphates marins du Miocène et du Pléistocène, qui reflètent la paléo-variation de l'eau de mer au cours du temps, a montré que cela n'a pas toujours été le cas par le passé. Ainsi, à 22 Ma, une incursion du δ44Ca vers des valeurs plus positives suggère que l'intensité des flux entrants et sortants a varié, mais non leur signature isotopique.
Drouet, Thomas. „Etude de l'origine du calcium dans les écosystèmes forestiers par les méthodes de géochimie et de dendrochime isotopiques du strontium“. Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210940.
Der volle Inhalt der QuelleEl, Kilany Aïda. „Hydrologie et cycles biogéochimiques du soufre dans deux bassins marginaux de Méditerranée pendant la Crise de Salinité Messinienne“. Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC107/document.
Der volle Inhalt der QuelleThe formation of gypsum (CaSO4.2H2O) in Messinian Mediterranean marginal basins is controlled by basin restriction and the local hydrological cycle. Acting together, evaporation, river input and restricted water exchange with the Mediterranean basin bring about the chemical conditions for gypsum formation. Basin restriction also leads to enhanced microbial oxygen consumption, anoxia, and the triggering of active biogeochemical sulfur cycling. In this work I use the stable isotopic composition of gypsum as a proxy of water and sulphur cycling in the marginal basins. The goal is to better understand the hydrological and geochemical conditions that lead to gypsum precipitation. This is an open question, especially since recent work has proposed that part of the gypsum in marginal basins precipitated from a low-salinity (£ 35 PSU) water column - a hypothesis that seems unrealistic based on simple geochemical considerations. I carried out a high-resolution isotopic study of gypsum layers composing gypsum-marl cycles in the Messinian Caltanissetta (Sicily) and Piedmont (north-western Italy) marginal basins (CB and PB, respectively). These gypsum-marl cycles are thought to be the sedimentary expression of astronomical precession cycles (~20 kyr), during which the marginal basins experienced a succession of arid and wet conditions. The hydrological cycle was tracked by measuring the oxygen and hydrogen isotope composition of the gypsum-bound water molecule; the biogeochemical sulfur cycle was tracked by measuring the sulfur and oxygen isotope composition of the gypsum sulfate ion. I observed that: (1) the isotopes of gypsum-bound water are considerably lighter than those expected for gypsum precipitated via evaporation of seawater, and (2) water in the Caltanissetta basin was characterized by a higher deuterium deficit - compared to its 18O content - than water in the Piedmont basin. In conjunction with a hydrological box-model, these observations imply that (1) gypsum precipitation takes place under the influence of large riverine freshwater fluxes, particularly in the North Piedmont basin, that result in very low salinities (27-50 psu in CB and 10-42 psu in PB) and (2) the contrast in deuterium deficit results from atmospheric humidity-drived difference in the deuterieum content of the evaporative flux, implying that the atmosphere over the CB was drier than that over the PB. Thus, a latitudinal relative humidity gradient similar to the modern one existed in the Messinian, providing evidence for a Mediterranean-like climate in the region 5.97 million years ago. The isotopic composition of the gypsum sulfate ion suggests that it originates from coeval sea water. Deviation from the Messinian marine signature, however, highlights an active biogeochemical sulfur cycle driven by sulfate reduction and sulfide oxidation. In particular, (1) 18O- and 34S-rich sulfate in the Piedmont basin indicates sulfate-reduction in a geochemically open system where 32S is lost to sedimentary sulfide minerals, and (2) significant 18O-enrichment (CB) or 18O-depletion (PB), in samples where the 34S concent is that of seawater, indicates re-oxidation of sulphide in a geochemically closed system of an evaporative (CB) or dilution (PB) marginal basin. A strong relation between the hydrological cycle and the biogeochemical cycle is thus highlighted in marginal Messinian basins
Tarits, Corinne. „Etude des variations de composition isotopique du carbone et de l'oxygène dans le domaine de la précipitation spontanée homogène du carbonate de calcium : modélisation du comportement isotopique du carbone dans ce domaine“. Paris 5, 1990. http://www.theses.fr/1990PA05P617.
Der volle Inhalt der QuelleBrazier, Jean-Michel. „Rôle des phases minérales des sols en tant que réservoirs de nutriments : approche expérimentale (abiotique), en milieu naturel et multi-isotopique (isotopes stables Ca-Sr)“. Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAH005/document.
Der volle Inhalt der QuelleThis PhD thesis examined the mechanisms of storage and release, from and elementary and isotopically point of view, of calcium (Ca) and strontium (Sr) onto or into mineral phases commonly encountered within soils (primary minerals, clay minerals, oxy-hydroxides, pedogenic carbonate). A robust δ88Sr measurements method had to be developed in the laboratory and validated by the measurement of international reference materials, mostly never measured in the literature. The results of this work show that Ca adsorption onto phyllosilicate minerals generates a quantifiable isotopic fractionation by preferential uptake of the light isotope (40Ca) under our experimental conditions when the minerals have a significant structural charge and specific surface area and/or an interlayer space open to hydrated cations adsorption. A study on rhizoliths in natural environment has also highlighted that the combination of Ca and Sr isotopes allows an effective tracing of sources and mechanisms in the problematic related to the storage of these two elements within soils
Dubousset, Lucie. „Effet d'une restriction en sulfate couplée ou non à une limitation en nitrate sur l'efficience de mobilisation du S et du N foliaire chez le colza d'hiver (Brassica napus L. ) : Thèse soutenue sur un ensemble de travaux“. Caen, 2009. http://www.theses.fr/2009CAEN2074.
Der volle Inhalt der QuelleThe survey of the physiological and agronomic impacts of a mineral sulphur (S) limitation in oilseed rape (Brassica napus L. ) – an oleagenous very demanding in S but characterized by a weak S use efficiency (SUE) – is of particular interest in the current context of S impoverishment in soils associated with the decrease of atmospheric deposits. Thus, the goals were targeted to (1) determine the stages of development the most sensitive to the S limitation, (2) identify the processes of S and N mobilization/allocation (via 15N/34S labellings) and (3) evaluate the effects of the N availability on these processes. An allometric relationship similar to N with shoot biomass could not be established for S. Whatever the availability in N, a sequestration of sulphate in leaves of plants well supplied with S was revealed in greenhouse and in field experiments. In case of S limitation, the sulfate stored in leaves would be efficiently remobilized towards growing tissues via the induction of tonoplastic transporters (BnSultr4;1 and BnSultr4;2) involved in its efflux. A S restriction at the stage C2 (bolting) affects the N use efficiency. The grain filling and the oil quality depend on the S availability between C2 and D2 (visible buds). Overall results show that the weak SUE in oilseed rape is related to a weak mobilization of sulphate in leaves and that an adapted S fertilization covering the requirements until the beginning of flowering would allow improving the SUE while maintaining seed yield and quality
Abdallah, Maha. „Etude de l’allocation et de la mobilisation du soufre (S) chez le colza d’hiver (Brassica napus L. ) soumis à une oligotrophisation en S“. Caen, 2010. http://www.theses.fr/2010CAEN2069.
Der volle Inhalt der QuelleOilseed rape (Brassica napus L. ) is supposed to be sensitive to S limitation which negatively affects growth. Nevertheless, as little studies clearly assessed the impact of short or long term mineral S limitation, we analyzed its effects on i) biomass production, ii) N and S uptake by , 15N and 34S labelling iii) relative gene expression of nitrate and sulphate transport systems, iv) N and S remobilization and v) leaf senescence dynamics during vegetative growth. The results showed that under short term S limitation and with sufficient initial S reserves, oilseed rape is able to maintain its growth according to the recycling of endogenous S reserves (mostly as sulphate) from old leaves while in the meantime, gene expression encoding sulphate tonoplastic transporters were up-regulated. S fluxes from uptake and S remobilization from leaves were mostly allocated to the roots. Only with both low initial S reserves and low mineral S availability (i. E. Long term S limitation), plant growth was reduced while one of the nitrate transporter gene expressions was steadily down-regulated and root nitrate uptake was also reduced. Moreover, leaf soluble proteins contents, total S, S recently taken up as 34S and sulphate contents in oldest leaves declined despite an up-regulation of the expression of genes encoding plasmalemmic or tonoplastic sulphate transporters. Compared to control plants, S limitation also delayed leaf senescence evaluated by molecular indicators and leaf protein degradation. Overall results demonstrated that the effect of S limitation should be estimated by taking into account plant initial S status, and particularly the sulphate content within the oldest leaves. Our results gave new perspectives for the improvement of Sulphur Use Efficiency and Nitrogen Use Efficiency, because of the tigh inter-connection between theses two metabolisms
Perrot, Frédéric. „Etude spectroscopique des isotopes 51,52,53Ca par décroissance β des noyaux riches en neutrons 51,52,53K et interaction effective dans la couche fp“. Université Louis Pasteur (Strasbourg) (1971-2008), 2004. https://publication-theses.unistra.fr/public/theses_doctorat/2004/PERROT_Frederic_2004.pdf.
Der volle Inhalt der QuelleThe study of neutron rich nuclei is a powerful tool to observe shell evolution with isospin far from stability. Recent experimental studies have pointed out a new magic number at N=32 with strong features for 52Ca. Indeed neutron rich calcium isotopes (N>29) are key nuclei to fix the effective neutron-neutron interaction in fp shell due to the simplicity of the Z=20 wave function. The study of 51,52,53Ca isotopes has been performed at the CERN-ISOLDE mass separator facility by beta-decay of 51,52,53K. The experimental set-up was composed of the TONNERRE and the LEND detector array dedicated to the observation of the delayed neutrons and of two MINIBALL clusters for gamma detection. A new method has been developed to determine the absolute decay number of K isotopes by modelling the time evolution of the ions extraction from the target-ion-source ensemble. Moreover, a lot of new bound and unbound states have been observed in 51,52,53Ca in a wide energy range up to 11 MeV. Shell model calculations have been performed in the fp shell and some monopole corrections in the T=1 isospin channel have been done, giving rise to a new KB3Gm effective interaction. Calculations with this interaction well agree with new spectroscopic results on 51,52,53Ca and predict a 2+ state around 2 MeV in 54Ca. Such a future experimental observation would sign the non appearence of a new magic number at N=34
Ngoyanadji, Nicolas. „Le gisement de Pb-Zn de Largentière (Ardèche-France) : apport de l'étude des inclusions fluides et des isotopes du soufre au problème de sa genèse“. Vandoeuvre-les-Nancy, INPL, 1988. http://www.theses.fr/1988NAN10051.
Der volle Inhalt der QuelleNgoyanadji, Nicolas. „Le Gisement de Pb-Zn de Largentière, Ardèche, France apport de l'étude des inclusions fluides et des isotopes du soufre au problème de sa genèse /“. Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37616891c.
Der volle Inhalt der QuelleBenhidjeb, Nadra. „Etude théorique et expérimentale de l'évolution de la structure poreuse lors de la sulfatation de la chaux“. Mulhouse, 1996. http://www.theses.fr/1996MULH0442.
Der volle Inhalt der QuelleEl, Kilany Aïda. „Hydrologie et cycles biogéochimiques du soufre dans deux bassins marginaux de Méditerranée pendant la Crise de Salinité Messinienne“. Electronic Thesis or Diss., Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC107.
Der volle Inhalt der QuelleThe formation of gypsum (CaSO4.2H2O) in Messinian Mediterranean marginal basins is controlled by basin restriction and the local hydrological cycle. Acting together, evaporation, river input and restricted water exchange with the Mediterranean basin bring about the chemical conditions for gypsum formation. Basin restriction also leads to enhanced microbial oxygen consumption, anoxia, and the triggering of active biogeochemical sulfur cycling. In this work I use the stable isotopic composition of gypsum as a proxy of water and sulphur cycling in the marginal basins. The goal is to better understand the hydrological and geochemical conditions that lead to gypsum precipitation. This is an open question, especially since recent work has proposed that part of the gypsum in marginal basins precipitated from a low-salinity (£ 35 PSU) water column - a hypothesis that seems unrealistic based on simple geochemical considerations. I carried out a high-resolution isotopic study of gypsum layers composing gypsum-marl cycles in the Messinian Caltanissetta (Sicily) and Piedmont (north-western Italy) marginal basins (CB and PB, respectively). These gypsum-marl cycles are thought to be the sedimentary expression of astronomical precession cycles (~20 kyr), during which the marginal basins experienced a succession of arid and wet conditions. The hydrological cycle was tracked by measuring the oxygen and hydrogen isotope composition of the gypsum-bound water molecule; the biogeochemical sulfur cycle was tracked by measuring the sulfur and oxygen isotope composition of the gypsum sulfate ion. I observed that: (1) the isotopes of gypsum-bound water are considerably lighter than those expected for gypsum precipitated via evaporation of seawater, and (2) water in the Caltanissetta basin was characterized by a higher deuterium deficit - compared to its 18O content - than water in the Piedmont basin. In conjunction with a hydrological box-model, these observations imply that (1) gypsum precipitation takes place under the influence of large riverine freshwater fluxes, particularly in the North Piedmont basin, that result in very low salinities (27-50 psu in CB and 10-42 psu in PB) and (2) the contrast in deuterium deficit results from atmospheric humidity-drived difference in the deuterieum content of the evaporative flux, implying that the atmosphere over the CB was drier than that over the PB. Thus, a latitudinal relative humidity gradient similar to the modern one existed in the Messinian, providing evidence for a Mediterranean-like climate in the region 5.97 million years ago. The isotopic composition of the gypsum sulfate ion suggests that it originates from coeval sea water. Deviation from the Messinian marine signature, however, highlights an active biogeochemical sulfur cycle driven by sulfate reduction and sulfide oxidation. In particular, (1) 18O- and 34S-rich sulfate in the Piedmont basin indicates sulfate-reduction in a geochemically open system where 32S is lost to sedimentary sulfide minerals, and (2) significant 18O-enrichment (CB) or 18O-depletion (PB), in samples where the 34S concent is that of seawater, indicates re-oxidation of sulphide in a geochemically closed system of an evaporative (CB) or dilution (PB) marginal basin. A strong relation between the hydrological cycle and the biogeochemical cycle is thus highlighted in marginal Messinian basins
Poszwa, Anne. „Utilisation des isotopes du strontium pour évaluer la dynamique des éléments minéraux dans des écosystèmes forestiers sous climat boréal, tempéré et tropical“. Nancy, 2000. http://docnum.univ-lorraine.fr/public/SCD_T_2000_0128_POSZWA.pdf.
Der volle Inhalt der QuelleTallec, Tiphaine. „Effets d'un double gradient azote/soufre sur la structure des communautés végétales de prairies bas-normandes : dynamique de l'acquisition des ressources minérales et des interactions compétitives“. Caen, 2008. http://www.theses.fr/2008CAEN2011.
Der volle Inhalt der QuelleThe importance of soil S depletion, due to an increased export from plant harvest combined with a decreased atmospheric S deposition, requires to study its impact on the dynamics of grassland communities, under different N supplies. A pluri-scale study was carried out in situ, and in mesocosm consisting of populations or of model communities with 4 dominant species. Before and after defoliation, the relative production, the abundance and the competitiveness of the species were analyzed through their N and S use efficiency using a simultaneous 15N/34S labelling. Their response was conditioned by their physiological ability to mobilize resources, but also to compete for the latter in N-rich soil. A strong co-regulation between N and S metabolisms was highlighted. An increased S availability enhanced production for all scale situations. The S effects on Poaceae appeared only at high N availability, by a stimulation of their soil N use efficiency, optimizing N fertilizer use. Those on clover induced the stimulation (i) of the atmospheric N fixation, even at high N availability, (ii) of its vegetative multiplication and (iii) of N reserves accumulation in stolons. In situ and in community, S input increased the abundance of dominated species and, with high N fertilization, maintained or increased specific diversity. Overall, a rational S input appeared as an important tool for grassland management
Lefèvre, Émilie. „Étude de la minéralisation de la nappe de la craie sous pressions naturelles et anthropiques : application à la présence de l'azote, du soufre et du nickel dans les eaux souterraines“. Lille 1, 2006. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2006/50376_2006_17.pdf.
Der volle Inhalt der QuelleRollion-Bard, Claire. „Variabilité des isotopes de l'oxygène dans les coraux Porites : développement et implications des microanalyses d'isotopes stables (B, C ET O) par sonde ionique“. Nancy 1, 2001. http://docnum.univ-lorraine.fr/public/INPL_T_2001_ROLLION-BARD_C.pdf.
Der volle Inhalt der QuelleCourt, Mélanie. „Étude des cycles du Ca et Mg dans cinq hêtraies du nord de la France et des modifications induites par un amendement calco-magnésien : utilisation combinée des approches élémentaires et isotopiques (δ26/24Mg, δ44/40Ca et 87Sr/86Sr)“. Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0248/document.
Der volle Inhalt der QuelleIn France, many forest ecosystems grow on acidic and nutrient poor soils. In numerous cases, the chemical fertility of forest soils is slowly degrading due to increasing external pressures (e.g. decreasing atmospheric inputs, increasing biomass exportations) and is a growing concern in the international forest community. Forest management often must resort to restauration/remediation practices to ensure the sustainability of the ecosystem. Forest liming with a carbonate product is a known practice to reduce soil acidity, globally improve the ecosystem functioning and compensate nutrient losses caused by biomass harvest and exportation. However, our understanding of the effects of liming on magnesium and calcium biogeochemical processes and cycling in forest ecosystems is still incomplete. This study focuses on the fate of magnesium and calcium originating from the dissolution of liming products in the soils and trees of five beech forests located in Northern France over a period up to 45 years. In order to do so, “conventional” total-element approaches were combined with a multi-isotopic approach (26/24Mg, 44/40Ca et 87/86Sr). At all five sites, the data measured in control plots throughout the study period suggest that the exchangeable pools of nutrient cations in the soil has decreased over the last several decades and that this trend, together with the low chemical fertility level of the soil, was reflected in foliar nutrition (Ca, Mg, K, P). Compared to the control plots, soil exchangeable pools of Mg and Ca in the 0-40cm layer in the limed plots increased during the first decade after liming but differences were no longer observable in soil pools after 20 to 30 years. However, the effect of liming on tree nutrition was still observed after 40 years, most probably because the biological cycling of these elements was enhanced by the lime input. The ecosystem response to the lime input varied between sites depending on the nature of the liming product (CaCO3 or Ca-MgCO3) and the initial chemical fertility level of the soil, the poorest sites showing the strongest responses. The natural variations of Mg, Ca and Sr isotopic ratios combined with conventional approaches highlight the importance of the BIO component of the biogeochemical cycling of Mg and Ca in the studied low chemical fertility beech forests. These isotopic tools also enabled to show the long-lasting incorporation of the Mg and Ca released from the liming product in the biological cycle and highlight the changes in the biogeochemical functioning of these forest ecosystems after the liming operation
Leblondel, Gérard. „Influences hormonales sur la distribution de 14 éléments chez le rat : contribution à l'étude de l'homéostasie des éléments“. Angers, 1988. http://www.theses.fr/1988ANGE0001.
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