Le soufre est un composant volatil important des magmas qui présente différents états d'oxydation en fonction des conditions d’oxydoréduction et de la phase dans laquelle il se trouve : dans le liquide silicaté, il est typiquement dissous comme S⁶⁺ et/ou S²⁻ , dans la phase gazeuse il se trouve principalement comme SO₂ (S⁴⁺ ) et H₂S (S²⁻). L’Etna, pour lequel les conditions d’oxydoréduction sont faiblement contraintes, est utilisée comme cas d’étude pour examiner le comportement du soufre dans les magmas basaltiques hydratés pendant la différenciation et le dégazage. Cette recherche combine l'étude des inclusions vitreuses avec une étude expérimentale en conditions magmatiques sur la solubilité du S dans les basaltes alcalins hydratés.Les résultats expérimentaux suggèrent l’important contrôle de la ƒO₂ sur la teneur en S dans les magmas hydratés de l’Etna, et le partage du S entre les phases fluid and liquid. Les inclusions vitreuses ont été piégées à différentes profondeurs à l'intérieur du système magmatique. Elles décrivent une tendance continue de différenciation, marquée par une cristallisation fractionnée, à partir de la composition picritique (FS) vers le basalte plus récent dégazé (2013). Le contenu en S dans le liquide de l'Etna est extrêmement variable et atteint 4150 ppm dans les inclusions vitreuses les plus primitives. Les spectres XANES Fe³⁺/ΣFe des certaines inclusions vitreuses donnent des rapports Fe³⁺/ΣFe généralement décroissants à partir du liquide le plus primitif (FS) jusqu’au plus évolué (2013). Les simulations effectué par le logiciel MELTS confirme que la diminution du rapport Fe³⁺/ΣFe est principalement due au processus de différenciation magmatique, renforcé par le dégazage du S à ƒO₂ < NNO + 1. Cette réduction du magma provoque à son tour la diminution de la solubilité du S dans les basaltes hydratés de l’Etna, et peut constituer un éventuel activateur de l’exsolution du S, à l’origine de l’important dégazage du S observé au cours des dernières décennies à l’Etna. / Sulfur is an important volatile component of magmas that presents different oxidation states, depending on the redox conditions and on the phase of occurrence: in silicate melts it is typically dissolved as S⁶⁺ and/or S²⁻ , in the gas phase it occurs principally as SO₂ (S⁴⁺ ) and H₂S (S²⁻). Mount Etna, in which magmatic redox conditions are poorly constrained, is used as a case study to investigate sulfur behavior in hydrous basaltic magmas during magma differentiation and degassing. This research integrates the study of natural olivine-hosted melt inclusions with an experimental study on S solubility in hydrous alkali basalts at magmatic conditions.Experimental results suggest the important control of ƒO₂ on the S abundance in Etnean hydrous magma and its partitioning between fluid and melt phases. Melt inclusions were entrapped at different depths inside the magmatic system (up to ~ 18 km, below crater level). They delineate a continuous differentiation trend, marked by fractional crystallization, from the picritic basalt (FS) toward the most evolved and degassed (2013) basalt. S content in Etnean melt is extremely variable and reaches 4150 ppm in the primitive melt inclusions. XANES Fe³⁺/ΣFe spectra in some glass inclusions, resulted in the generally decreasing of Fe³⁺/ΣFe ratios from the most primitive (FS) to the most evolved (2013) melts. MELTS software confirms that the Fe³⁺/ΣFe decrease is due principally to the melt differentiation process, enhanced to the S degassing at ƒO₂ < NNO+1. Magma reduction, in turn, induces the decrease of the sulfur solubility in the hydrous Etnean basalt, as well as of the sulfide saturation, and may constitute a possible enhancer of S exsolution, triggering the important S degassing observed in the last decades in Mt. Etna.

Ce projet s’inscrit dans le cadre d’une étude fondamentale sur la spéciation du technétium en milieu fortement acide. Le comportement de Tc(VII) en milieu HTFMS a été étudié en absence et en présence d’irradiation α. Dans ces deux conditions différentes, les résultats spectrophotométriques de réduction de Tc (VII) obtenus pour les mélanges HTFMS-xH₂O sont similaires. L’analyse par SAX indique la formation d’un dimère cyclique de Tc(IV) complexé aux ligands triflates et formulé Tc₂O₂(CF₃SO₃)₄(H₂O)₄. Ce composé est linéarisé en TcIV-O-TcIV quand la concentration de HTFMS augmente. Dans HTFMS à +98% (CHTFMS=11,15 M), le Tc(VII) protoné, de formule TcO₃(OH)(H₂O)₂, stabilisé en absence de rayonnements ionisants externes est réduit en Tc(V) sous irradiation α. La caractérisation structurale par la spectroscopie EXAFS sur la base des calculs DFT suggère la formation d’un complexe monomère de Tc(V) avec les ligands triflates. Les deux composés [OTc(F₃CSO₃)₂(H₂O)₂]⁺ et [OTc(F₃CSO₃)₂(OH)₂]⁻ ont été proposées. En milieu H₂SO₄ concentré (CH₂SO₄ ≥ 12 M), des expériences de radiolyse α de Tc(VII) ont été menées afin de pouvoir comparer le comportement radiolytique de Tc(VII) dans les deux milieux apparentés HTFMS et H₂SO₄. Les études XANES montrent que la réduction radiolytique de Tc(VII) contribue à la formation d’un mélange de Tc(V) et Tc(VII) dans H₂SO₄ 13 M et à Tc(V) à 18 M en H₂SO₄. L’analyse des spectres EXAFS indique la formation de complexes monomères [TcO(HSO₄)₃(H₂O)₂] et [TcO(HSO₄)₃(H₂O)(OH)]⁻ en milieu H₂SO₄ 13 M et des espèces [Tc(HSO₄)₃(SO₄)(H₂O)] et [Tc(HSO₄)₃(SO₄)(OH)]⁻. / This project is part of the fundamental study of technetium speciation in highly acidic medium. The behaviour of technetium in HTFMS was carried out in the absence then in the presence of α irradiation. Given these two different conditions, spectrophotometric results of Tc(VII) reduction are similar. XAS analysis indicates the formation of a cyclic dimer of Tc(IV) complexed to triflate ligands and formulated asTc₂O₂(CF₃SO₃)₄(H₂O)₄. This compound is linearized to TcIV-O-TcIV with the increase of HTFMS concentration. At high concentration of HTFMS +98% (11.15 M), the protonated species TcO₃(OH)(H₂O)₂ which is formed in the absence of external ionizing radiations, is reduced to the V oxidation state under α irradiation. Structural characterization by EXAFS spectroscopy and DFT calculations suggests the formation of monomer species of Tc(V)-triflate complexes where [OTc(F₃CSO₃)₂(H₂O)₂]⁺ and [OTc(F₃CSO₃)₂(OH)₂]⁻ compounds were proposed. In concentrated H₂SO₄ (CH₂SO₄ ≥ 12 M), α-radiolysis experiments of Tc(VII) were performed in order to compare the radiolytic behaviour of Tc(VII) in both comparable media HTFMS and H₂SO₄. XANES studies show that radiolytic reduction of Tc(VII) leads to the formation of Tc(V)-Tc(VII) mixture in H₂SO₄ 13 M and just Tc(V) in 18 M of H₂SO₄. The analysis of EXAFS spectra is consistent with the formation of [TcO(HSO₄)₃(H₂O)₂] and [TcO(HSO₄)₃(H2O)(OH)]⁻ monomer complexes in H₂SO₄ 13 M and [Tc(HSO₄)₃(SO₄)(H₂O)] and [Tc(HSO₄)₃(SO₄)(OH)]⁻ species at 18 M of H₂SO₄.

Não há dúvidas que a exitosa exploração do Cerrado só foi possível graças às pesquisas que desenvolveram tecnologias de correção e adubação específicas para esse ambiente. Apesar de estar consolidado como um dos principais ambientes de produção agropecuária do mundo, as pesquisas devem avançar contribuindo, cada vez mais, com aumento na eficiência do uso do fósforo (P), por ser o elemento mais limitante para produção agrícola nesse ambiente. Devido às características dos solos dessa região, parte do P aplicado é retido pelo solo em formas que as plantas não conseguem absorver, resultando na acumulação de quantidades significativas do nutriente no solo. Apesar de não ser um assunto relativamente novo e do grande número de trabalhos, o tema avaliação da disponibilidade de fósforo do solo ainda provoca dúvidas. Além dos estudos em que é avaliada a eficiência de diversos extratores como Mehlich-1 e resina de troca aniônica, outras técnicas passaram a ser utilizadas para esse fim. Estudos objetivando avaliar a distribuição (dinâmica) do fósforo nas diferentes frações do solo e as mudanças nessa distribuição em função do manejo aplicado aos cultivos e, também, do tempo de cultivo, têm sido conduzidos com crescente intensidade. Estudos também têm sido conduzidos buscando identificar as formas de acumulação de P no solo. Para isso, modernas técnicas espectroscópicas, como por exemplo, a espectroscopia baseada em luz synchrotron, têm sido utilizadas como uma poderosa ferramenta, auxiliando na identificação dos compostos presentes no solo. Face ao exposto, objetivou-se avaliar as alterações no fósforo disponível e nas frações e formas de fósforo em solo de Cerrado submetido ao manejo em semeadura direta com diferentes tempos de cultivo. Foram coletadas amostras compostas em quatro áreas que se encontravam no momento da coleta com 5, 8, 12 e 18 anos de cultivo desde a abertura das áreas, e também numa área sob vegetação nativa. O fósforo disponível foi extraído por Mehlich-1 e resina de troca aniônica. As amostras foram submetidas ao fracionamento químico de fósforo e espectroscopia de alta resolução da borda de absorção (XANES - X-ray absorption near edge structure). Observou-se que, de maneira geral, os teores de fósforo no solo foram sempre mais altos nas áreas cultivadas, principalmente na camada superficial, em comparação aos da área com vegetação nativa, o que reflete o impacto das adubações fosfatadas. A aplicação superficial do fertilizante fosfatado gerou nítidos gradientes de P no perfil do solo, principalmente para as frações lábeis e moderadamente lábeis, sendo essas frações as que sofreram maior influência do fertilizante quando comparadas às frações de menor disponibilidade. Considerando-se os mesmos extratores, os teores das frações orgânicas foram maiores em comparação às correspondentes frações inorgânicas. As formas de fósforo nos solos estudados foram predominantemente associadas ao alumínio e ao ferro, com destaque para o nutriente associado ao alumínio, sendo que, com o ferro, a associação ocorreu predominantemente por meio de fenômenos de adsorção em detrimento de fenômenos de precipitação. / There is no doubt that the successful exploitation of the Cerrado was only possible due to the research that developed specific correction and fertilization technologies to this particular environment. Due to the characteristics of soils in the region, part of applied phosphorus (P) is retained by the soil in plant unavailable forms, resulting in accumulation of significant amounts of nutrient in the soil. Despite not being a relatively new issue and the large number of research performed on this topic, the assessment of the soil P availability still raise important questions. In addition to studies in which the efficiency of various extractants have been tested, such as Mehlich-1 and anion exchange resin, other techniques are being used for this purpose. Studies for evaluating the P distribution (dynamic) in different soil fractions and the changes in this fractions due to the management applied to crops and also the time of cultivation have been conducted with increasing intensity. Studies have also been carried out in order to identify the forms of P accumulation in soils. For this purpose, modern spectroscopic techniques such as spectroscopy based on synchrotron light source, have been used as a powerful tool, assisting in the identification of P compounds presents in the soil. The aims of this study were to evaluate the changes in available, fractions and forms of P in soils of Cerrado with different times under no-till cultivation system. Composite soil samples were collected in four areas under 5, 8, 12 and 18 years of no-till cultivation since the areas were opened, and also in a area under native vegetation. The soil in the area was classified as Typic Hapludox and the areas were cultivated alternating crops of soybeans, corn and cotton. Available P was extracted by Mehlich - 1 and anion exchange resin. The samples were subjected to Hedley´s chemical fractionation of P and X- ray absorption near edge structure (XANES). It was observed that, in general, the levels of P in the soil were always higher in cultivated areas, mainly in the topsoil, when compared to the area under native vegetation, which reflects the impact of phosphate fertilization. Surface application of phosphate fertilizer produced sharp gradients of P in the soil profile, especially for both labile and moderately labile fractions, and these fractions suffered the greatest influence of fertilizer compared to fractions of lower availability. Considering the same extractants, the organic P fractions contents were higher compared to the corresponding inorganic fractions. Forms of phosphorus in soils were predominantly associated with aluminum (Al) and iron (Fe), especially P associated with Al, and with Fe the association occurred predominantly through adsorption phenomenon rather than precipitation reactions.

Supplementation of trace metals such as Co and Ni may improve anaerobic digestion of organic material for biogas formation. Which trace metals that are needed and the quantity to apply are, at least partly, related to metal speciation and bioavailability. According to the common perception, metals have to be dissolved to be available for microbial uptake. However, the impact of trace metal speciation on bioavailability is still unclear. The purpose of the present study was to investigate the effect of Fe-, Co- and Ni-addition on the biogas process performance of stillage-fed lab-scale biogas tank reactors. Metal speciation was determined by sequential extraction (SE), extraction of acid volatile sulfides (AVS) and continuously extracted metals (AVS-Me). Sulfur forms, which may be associated to metal speciation, were studied with S XANES (sulfur X-ray absorption near edge structure). The effect of different Co- and Ni-concentrations on process microflora composition was examined with quantitative PCR (qPCR) and 454-pyrosequencing. The results showed that Co- and Ni-supplementation stimulated and stabilized the biogas process performance by increasing methane production and substrate utilization and by establishing low concentrations of volatile fatty acids. 10-20% of the total Co-amount was found in the dissolved phase, which shows that Co was relatively available for microbial uptake. Nickel was entirely associated to organic matter/sulfides and AVS, and was therefore considered to be non-bioavailable. Nevertheless, Ni-supplementation had stimulatory effects on the biogas process performance. This implies that Ni was available for microbial uptake despite its extensive association to sulfides and that other mechanisms than solubility govern the availability of this trace metal. The microbial analyzes revealed that it was primarily the methane producers which were affected by the concentration of Co and Ni. At stimulatory Co- and Ni-concentrations, the archaeal methanogenic community was dominated by aceticlastic Methanosarcinales. At lower Co- or Ni-levels, when biogas process performance was poor, an increase in hydrogenotrophic Methanomicrobiales was observed. This indicates a shift in the methanogenic flora, from being dominated by acetate utilizers to increased importance of hydrogen utilizers, and that the former was more dependent on Co and Ni. / Tillsats av spårmetaller kan förbättra rötning av organiskt material till biogas. Typ och mängd av respektive spårmetall som behöver tillsättas för att uppnå stimulerande effekter, varierar mellan processer. Detta är delvis kopplat till specieringen och biotillgängligheten av metallerna. Endast fria metalljoner och vissa metallkomplex antas vara tillgängliga för mikrobiellt upptag. Det är dock i många fall oklart hur metallernas speciering påverkar biotillgängligheten. Syftet med föreliggande studie var därför att undersöka effekten av tillsats av Fe, Co och Ni för biogasproduktion från drank, en restprodukt i produktion av bioetanol från spannmål, samt att undersöka hur dessa metallers speciering påverkar deras biotillgänglighet. Effekten av tillsatserna av Fe, Co och Ni undersöktes på biogasreaktorer i lab-skala. Metallernas speciering bestämdes genom sekventiell extraktion (SE), extraktion av AVS (acid volatile sulfide) och kontinuerligt extraherade metaller (AVS-Me). Svavelformer med betydelse för metallspeciering studerades med S XANES (sulfur X-ray absorption near edge structure). Effekten av olika Co- och Ni-koncentrationer på processens mikroflora undersöktes molekylärbiologiskt med kvantitativ PCR (qPCR) och 454-pyrosekvensering. Resultaten visade att Co och Ni stimulerade och stabiliserade biogasprocessen genom ökad metanproduktion, ökad utrötningsgrad samt låga halter av flyktiga fettsyror i det studerade systemet. 10-20% av totala mängden Co återfanns i löst fas, vilket visar att Co var relativt lättillgängligt för mikroorganismerna. Nickel var däremot enbart bundet till organiskt material/sulfider och AVS och kunde alltså betraktas som otillgängligt. Trots detta hade även tillsatsen av Ni stimulerande effekter på biogasprocessen. Det innebär att mikroorganismerna har förmåga att komma åt Ni bundet i svårlösliga sulfidföreningar och att andra mekanismer än löslighet reglerar tillgängligheten av denna spårmetall. De molekylärbiologiska analyserna visade att framför allt de metanbildande mikroorganismerna påverkades av halten av Co och Ni. De halter, som gav välfungerande processer, dominerades helt av acetiklastiska Methanosarcinales. Vid lägre halter av Co eller Ni, då processerna gick sämre, tillkom vätgasutnyttjande metanogener. Det tyder på ett skift i bildningen av metan från att ha dominerats av acetatklyvning till att vätgasutnyttjarna fått större betydelse och att de förra är mer beroende av Co och Ni.

Les réactions d'oxydoréduction de l'antimoine (V) et (III) avec la mackinawite (FeS) et du plutonium (III) et (V) avec plusieurs minéraux à fer(II) et des oxydes de fer(III) ont été étudiées dans des conditions d'anoxie. La spectroscopie d'absorption des rayons X fut utilisée pour l'analyse de l'état d'oxydation et de la structure locale du Sb et Pu associés à la phase solide. Après réaction avec la mackinawite, la chukanovite et la magnétite, PuO2, Pu(III) ou des mixtures des deux états d'oxydation ont été observé. A la surface de la magnétite un complexe tridenté du Pu(III) a pu être mis en évidence à l'aide des spectres EXAFS couplé à une simulation de Monte-Carlo utilisant le code de calcul Feff. La quantité relative de Pu(III) est fonction de l'espèce minérale, du ratio solide/liquide, des valeurs pe et pH du système et, potentiellement, de la taille de particule et de la cristallinité de la phase solide de PuO2 en présence de laquelle le Pu(III) existe. Avec la mackinawite à pH 6,2 et à une occupation de surface de 67 nmol/m2 et avec la magnétite jusqu'à pH 8.4 et 56 nmol/m2 de Pu, uniquement du Pu(III) fut trouvé associé à la phase solide. Avec la maghémite contenant du fer(II) résiduel à pH6 Pu(III) et Pu(IV) était, probablement, présents dans des complexes de surfaces similaire à celui formé par le Pu(III) sur la magnétite. Dans les conditions expérimentales (couverture de surface ≤ 77 nmol/m2), aucune formation de PuO2 ne fut observé. Après réaction avec l'hématite et la goethite Pu(IV) était l'état d'oxydation prédominant associé à la phase solide. La sorption et la réduction du Sb(V) avec la mackinawite était fortement fonction du pH. A pH acide la sorption était rapide et Sb(V) fut complètement réduit en Sb(III), formant un complexe Sb(III)-S3 probablement associé à la surface de la mackinawite. La réduction du Sb(V) était couplée à l'oxydation de la mackinawite et la greigite (Fe3S4) fut détectée par XRD. A pH basique, la sorption du Sb(V) est lente et la réduction vers le Sb(III) n'était complète qu'à des ratios de Sb/FeS très bas. Pour des valeurs plus élevé de Sb/FeS la sorption de Sb se faisait en partie par la réduction envers le complexe de Sb(III)-S3 et en partie par une co-précipitation avec le Fe(III). Il a pu être démontré que les minéraux à fer(II) peuvent effectivement contribuer à la réduction et à l'immobilisation de l'antimoine et du plutonium qui sont des contaminants environnementaux d'importance croissante. / Redox reactions of Sb(V) and Sb(III) with mackinawite (FeS) and of aqueous Pu(III) and Pu(V) with various Fe(II)-bearing minerals and Fe(III)-oxides have been investigated under anoxic conditions. X-ray absorption spectroscopy was used to analyze oxidation state and local coordination environment of Sb and Pu associated with the solid phase. After reaction with mackinawite, chukanovite and magnetite, PuO2, Pu(III) or mixtures of the two oxidation states were observed. On magnetite, a tridentate Pu(III) surface complex could be identified from EXAFS combined with Feff-Monte-Carlo simulation. The relative amount of Pu(III) depends on the type of mineral, the solid/solution ratio, the system pe and pH, and, potentially, the particle size and crystallinity of the formed PuO2 solid phase. With mackinawite at pH 6.2 and a surface loading of 67 nmol/m2 and with magnetite up to pH 8.4 and a surface loading of 56 nmol/m2, only Pu(III) was identified associated with the solid phase. With maghemite containing residual Fe(II) at pH6, Pu(III) and Pu(IV) were present in, probably, inner-sphere surface complexes similar to the one formed by Pu(III) on magnetite. Under the given conditions (surface loadings ≤ 77 nmol/m2) formation of PuO2 was not observed. After reaction with hematite and goethite, Pu(IV) was the predominant oxidation state associated with the solid phase. Sorption and reduction of Sb(V) on mackinawite were strongly pH dependent. At acidic pH, sorption was fast and Sb(V) was completely reduced to an Sb(III)-sulfide complex associated with the solid phase. Reduction of Sb(V) was coupled to oxidation of mackinawite and formation of a greigite (Fe3S4) phase could be observed by XRD. At basic pH, Sb(V) was slowly removed from solution and reduction to Sb(III) was complete only at very small Sb/FeS ratios. At higher Sb/FeS, Sb(V) removal occurred partly through reduction to solid phase associated Sb(III)-S3 and partly through co-precipitation with Fe(III). In conclusion, it could be shown that Fe(II) bearing minerals can effectively contribute to the reduction and immobilization of antimony and plutonium, two contaminants of growing environmental importance.

Dans le système YbMn6Ge6-xSnx, l’ytterbium de valence intermédiaire (v.i.) s’ordonne magnétiquement à des températures étonnamment élevées (jusqu’à TYb~125 K). Ce travail contribue à une meilleure compréhension des propriétés physiques de ces alliages grâce à la stabilisation de nouveaux composés dans la gamme de concentration 4,6<x<5,3. Des expériences extrêmement sensibles utilisant le rayonnement synchrotron (XANES, XMCD) ont permis de situer l’instabilité magnétique d’Yb vers x~5 ,2. Le diagramme de phase magnétique (x,T) a pu être complété. Il montre une étroite ressemblance avec le diagramme de Doniach. Dans les systèmes classiques à base d’Yb v.i., les propriétés physiques sont interprétées dans le cadre d’une compétition entre effet Kondo et interactions RKKY. La particularité du système YbMn6Ge6-xSnx est la présence d’un sous-réseau magnétique de Mn qui est très probablement à l’origine des propriétés singulières d’Yb : TYb élevées et existence de mYb jusqu’à des valeurs de valence plus basse qu’à l’accoutumée (u>~2,8). Des expériences sous pression ont souligné l’analogie entre les effets de pression mécanique et chimique. L’augmentation de pression favorise le caractère trivalent et le magnétisme d’Yb. La 2nde partie de ce travail constitue une ouverture vers les matériaux pour les applications magnétocaloriques haute température telles que les pompes à chaleur ou la conversion d’énergie. Elle concerne l’étude des composés Mn4-xFexGa2Sn et Fe3Sn2 qui possèdent des températures de travail supérieures à la température ambiante. Leur EMC est modéré mais comparable à celui d’autres matériaux à transition de 2nd ordre fonctionnant dans la même gamme de température / In the YbMn6Ge6-xSnx system, intermediate valent Yb magnetically orders at an astonishingly high temperature (up to TYb~125 K). This work aims to improve the understanding of the physical properties of these compounds, with an emphasis on the concentration range 4.6<x<5.3. Some results have been obtained thanks to highly sensitive experimental techniques using synchrotron radiation (XANES, XMCD), and allowed us to locate the Yb magnetic instability near x~5.2. The magnetic phase diagram (x,T) has been completed and shows some similarities with the Doniach diagram. In conventional intermediate valent Yb systems, there is a competition between the Kondo screening and the magnetic exchange interactions of RKKY-type. The particularity of YbMn6Ge6-xSnx compounds is related to the strong 3d Mn-5d Yb exchange interaction and to the nonzero exchange field at the Yb site generated by the magnetic Mn sublattice. It is most likely responsible of very unusual Yb magnetic properties, in particular the astonishingly high magnetic ordering temperatures of low valence Yb (u>~2,8). External pressure experiments showed an analogy between mechanical and chemical pressure effects. Increasing the pressure favors trivalent state and Yb magnetism. In a second part, we investigated the magnetic and magnetocaloric properties of Mn4-xFexGa2Sn and Fe3Sn2. High temperature magnetocaloric applications, such as heat pump or heat conversion, need materials with high Curie temperature. These two compounds have working temperatures above 330 K. The magnetocaloric effect has been evaluated : the magnitude is moderate but close to other compounds with a second order transition near this temperature region.

Les vitraux du Moyen Âge, dont les pièces de verre contiennent du manganèse, sont fréquemment atteints d'une pathologie communément appelée "brunissement ". Ce phénomène, qui se traduit par la présence de taches brunes riches en manganèse en surface ou subsurface du verre limitant le passage de la lumière et gênant la lisibilité de l'œuvre, est peu documenté et son occurrence parmi les vitraux n'est pas précisément connue. Un des problèmes majeurs pour ce qui concerne la conservation/restauration des œuvres est l'absence de traitements efficaces et durables pour cette pathologie. En France actuellement, l'absence de traitement est donc préconisée, ce qui ne satisfait ni les architectes, ni les conservateurs, ni les restaurateurs. La connaissance approfondie des processus physico-chimiques à l'origine du phénomène de brunissement est donc nécessaire pour proposer des réponses aux questions et aux attentes des conservateurs/restaurateurs. Au cours de cette thèse un panel de 24 échantillons de verres de vitraux historiques et de 3 échantillons archéologiques ont été étudiés par des méthodes microscopiques et spectroscopiques afin i) d'établir des critères d'identification du phénomène de brunissement dû au manganèse et ii) d'obtenir des informations sur la nature des phases brunes et sur le degré d'oxydation du manganèse dans ces phases. Parallèlement à l'étude des échantillons anciens, des verres modèles de composition proche de celle des vitraux médiévaux ont été synthétisés avec deux objectifs : i) la compréhension de la réaction entre le manganèse et le fer et de l'influence des paramètres de fabrication sur la couleur des verres et ii) l'étude de l'influence que peuvent avoir les bactéries dans le développement du phénomène de brunissement

Phosphorus (P) is a plant macronutrient and soils located in tropical regions generally show low content of this element. Moreover, these soils are acidic and show high fixing capacity of phosphorus, substantially decreasing fertilizers efficiency. For this reason, annual P inputs to soils are required to obtain feasible crop yields. The main concern regarding P in agriculture is this element is extracted from mines that are being depleted. For this reason, it is necessary to develop recycling P technologies in order economize mineral resources and obtain benefits from low cost sources locally available. Bones are a P-rich material that could be employed for P recycling; however, this sub-product from meat industry needs to be treated prior use to ensure health safety. Pyrolysis is a technology that has gained attention because it does not affect bone mineral structure as does calcination, which is a standard treatment. Performing pyrolysis of bones generates a material called bone char and tests suggests that its efficiency is comparable to common soluble fertilizers obtained from P rocks. Another way to obtain higher crop P and other nutrients absorption as well as yield, is to stimulate symbiosis of plants with arbuscular mycorrhizal fungi (AMF), which are naturally found in soils. However, acidic soils from tropical regions generally difficult plant-AMF interaction due to high amount of exchangeable aluminum present. An alternative to overcome this issue would be to apply pyrolysis to organic wastes, generating a material termed biochar, which is rich in carbon, and sometimes nutrients, assisting AMF-plant symbiosis. Our aim was to produce through pyrolysis a set of bone chars in different temperatures (400, 550 and 800 °C) and atmospheric composition (sealed chamber, N2 flux and steam flux), and perform a detailed characterization of the resultant materials (chapter 1) to verify which possible factors are controlling bone char efficiency as fertilizer in a pot experiment labelled with 32P (chapter 2). To test the symbiotic pathway in P acquisition by plants through biochar use, two biochars from eucalyptus wood chips were produced at 300 and 700 °C and applied to a soil inoculated or non-inoculated with AMF. In this experiment we analyzed plant growth and colonization by AMF as well as nutrient absorption (chapter 3). Additionally, a trial with AMF spore germination evaluation was performed to investigate the possible inhibitory or positive effects of the biochars on AMF fungi. / O fósforo (P) é um macronutriente para as plantas e solos localizados em regiões tropicais geralmente apresentam baixo conteúdo deste elemento. Ainda, estes solos são ácidos e apresentam alta capacidade de fixação de P, diminuindo substancialmente a eficiência de fertilizantes. Por esta razão, adições anuais de P ao solo são requeridas para obtenção de produtividades de plantas economicamente viáveis. A principal preocupação em relação ao uso de P na agricultura é que este elemento é extraído de minas que estão sendo exauridas. Por esta razão, é necessário o desenvolvimento de tecnologias de reciclagem de P a fim de economizar recursos minerais e obter benefícios oriundos de fontes de baixo custo disponíveis localmente. Um material que é rico em P e que poderia ser empregado na reciclagem de fósforo é o osso animal, no entanto, este subproduto da indústria de carnes necessita ser tratado previamente ao uso para garantir segurança sanitária. A pirólise é umas tecnologias que tem recebido atenção porque seu emprego no tratamento de ossos não afeta a estrutura do material como a calcinação, que é um tratamento padrão. Realizar a pirólise de ossos gera um material denominado de carvão de osso (bone char, em inglês), o qual testes sugerem que a sua eficiência é comparável à fertilizantes solúveis convencionais obtidos a partir de rochas fosfáticas. Outra forma de obter maior absorção de P e nutrientes e maior produtividade de cultivos é através do estímulo da simbiose de plantas com micorrízicos arbusculares (FMA), estes naturalmente encontrados em solos. No entanto, solos ácidos de regiões tropicais geralmente dificultam a interação de plantas-FMA devido ao elevado teor de alumínio trocável presente. Uma alternativa para superar esse problema seria a aplicação de pirólise a resíduos orgânicos, gerando assim um material chamado biocarvão, o qual é rico em carbono, e as vezes nutrientes, e poderia auxiliar na simbiose de plantas com AMF. Nosso objetivo foi produzir através da pirólise um conjunto de biocarvões em diferentes temperaturas (400, 550 e 800 °C) e composições atmosférias (câmara selada, fluxo de N2 e fluxo de vapor d\'água) e realizar a caracterização dos materiais resultantes (capítulo 1) para verificar que possíveis fatores controlam a eficiência do carvão de osso em um experimento em vasos com marcação com 32P (capítulo 2). A fim de testar o viés simbiótico na aquisição de P pelas plantas com o uso de biocarvão, dois biocarvões de cavaco de eucalipto produzidos a 300 e 700 °C foram aplicados a um solo inoculado ou não com FMA (capítulo 3). Nesse experimento foram analizados o crescimento de plantas e colonização por FMA, como também a absorção de nutrientes. Adicionalmente, um teste com a germinação de esporos de FMA foi realizado para investiar possíveis effeitos positions ou inibitórios dos biochar em esporos de FMA.

Phosphorus (P) is a plant macronutrient and soils located in tropical regions generally show low content of this element. Moreover, these soils are acidic and show high fixing capacity of phosphorus, substantially decreasing fertilizers efficiency. For this reason, annual P inputs to soils are required to obtain feasible crop yields. The main concern regarding P in agriculture is this element is extracted from mines that are being depleted. For this reason, it is necessary to develop recycling P technologies in order economize mineral resources and obtain benefits from low cost sources locally available. Bones are a P-rich material that could be employed for P recycling; however, this sub-product from meat industry needs to be treated prior use to ensure health safety. Pyrolysis is a technology that has gained attention because it does not affect bone mineral structure as does calcination, which is a standard treatment. Performing pyrolysis of bones generates a material called bone char and tests suggests that its efficiency is comparable to common soluble fertilizers obtained from P rocks. Another way to obtain higher crop P and other nutrients absorption as well as yield, is to stimulate symbiosis of plants with arbuscular mycorrhizal fungi (AMF), which are naturally found in soils. However, acidic soils from tropical regions generally difficult plant-AMF interaction due to high amount of exchangeable aluminum present. An alternative to overcome this issue would be to apply pyrolysis to organic wastes, generating a material termed biochar, which is rich in carbon, and sometimes nutrients, assisting AMF-plant symbiosis. Our aim was to produce through pyrolysis a set of bone chars in different temperatures (400, 550 and 800 °C) and atmospheric composition (sealed chamber, N2 flux and steam flux), and perform a detailed characterization of the resultant materials (chapter 1) to verify which possible factors are controlling bone char efficiency as fertilizer in a pot experiment labelled with 32P (chapter 2). To test the symbiotic pathway in P acquisition by plants through biochar use, two biochars from eucalyptus wood chips were produced at 300 and 700 °C and applied to a soil inoculated or non-inoculated with AMF. In this experiment we analyzed plant growth and colonization by AMF as well as nutrient absorption (chapter 3). Additionally, a trial with AMF spore germination evaluation was performed to investigate the possible inhibitory or positive effects of the biochars on AMF fungi. / O fósforo (P) é um macronutriente para as plantas e solos localizados em regiões tropicais geralmente apresentam baixo conteúdo deste elemento. Ainda, estes solos são ácidos e apresentam alta capacidade de fixação de P, diminuindo substancialmente a eficiência de fertilizantes. Por esta razão, adições anuais de P ao solo são requeridas para obtenção de produtividades de plantas economicamente viáveis. A principal preocupação em relação ao uso de P na agricultura é que este elemento é extraído de minas que estão sendo exauridas. Por esta razão, é necessário o desenvolvimento de tecnologias de reciclagem de P a fim de economizar recursos minerais e obter benefícios oriundos de fontes de baixo custo disponíveis localmente. Um material que é rico em P e que poderia ser empregado na reciclagem de fósforo é o osso animal, no entanto, este subproduto da indústria de carnes necessita ser tratado previamente ao uso para garantir segurança sanitária. A pirólise é umas tecnologias que tem recebido atenção porque seu emprego no tratamento de ossos não afeta a estrutura do material como a calcinação, que é um tratamento padrão. Realizar a pirólise de ossos gera um material denominado de carvão de osso (bone char, em inglês), o qual testes sugerem que a sua eficiência é comparável à fertilizantes solúveis convencionais obtidos a partir de rochas fosfáticas. Outra forma de obter maior absorção de P e nutrientes e maior produtividade de cultivos é através do estímulo da simbiose de plantas com micorrízicos arbusculares (FMA), estes naturalmente encontrados em solos. No entanto, solos ácidos de regiões tropicais geralmente dificultam a interação de plantas-FMA devido ao elevado teor de alumínio trocável presente. Uma alternativa para superar esse problema seria a aplicação de pirólise a resíduos orgânicos, gerando assim um material chamado biocarvão, o qual é rico em carbono, e as vezes nutrientes, e poderia auxiliar na simbiose de plantas com AMF. Nosso objetivo foi produzir através da pirólise um conjunto de biocarvões em diferentes temperaturas (400, 550 e 800 °C) e composições atmosférias (câmara selada, fluxo de N2 e fluxo de vapor d\'água) e realizar a caracterização dos materiais resultantes (capítulo 1) para verificar que possíveis fatores controlam a eficiência do carvão de osso em um experimento em vasos com marcação com 32P (capítulo 2). A fim de testar o viés simbiótico na aquisição de P pelas plantas com o uso de biocarvão, dois biocarvões de cavaco de eucalipto produzidos a 300 e 700 °C foram aplicados a um solo inoculado ou não com FMA (capítulo 3). Nesse experimento foram analizados o crescimento de plantas e colonização por FMA, como também a absorção de nutrientes. Adicionalmente, um teste com a germinação de esporos de FMA foi realizado para investiar possíveis effeitos positions ou inibitórios dos biochar em esporos de FMA.

Internal loading of phosphorus (P) from lake sediments can delay the recovery of lakes from eutrophication for years to decades following decreases in external nutrient inputs. While internal P loading is a pervasive problem in freshwater systems, molecular speciation of P in benthic sediments of these systems remains poorly characterized. As different P species will exhibit different responses to changing sediment-water interface (SWI) geochemistry, quantifying P speciation in sediments is a critical step in understanding P dynamics in sediment-water systems. Here, various synchrotron-based techniques were employed to directly probe the bonding environments of P and iron (Fe) in natural and experimentally manipulated lake sediments in order to link chemical speciation to chemical behavior and to identify the geochemical drivers that mediate this linkage. We manipulated SWI redox conditions in mesocosm experiments to investigate the impacts of prolonged anoxia and redox oscillations on P mobility and speciation in sediments. Mesocosm experiments demonstrate that oscillating redox conditions near the SWI may drive accelerated P release from sediments relative to uninterrupted reducing conditions. Sediment P is found to be predominantly associated with Fe oxyhydroxides, calcium carbonate, and apatite minerals in three shallow hyper/eutrophic lakes in northern Vermont. In Missisquoi Bay and Lake Carmi, Fe redox cycling controls P mobility via precipitation and dissolution of Fe oxyhydroxides. In the hypereutrophic Shelburne Pond, the presence of Fe sulfides precludes redox-driven P cycling and P mobility is instead dominated by organic matter mineralization. Our results demonstrate that internal P loading can manifest differently in similar shallow lake systems due to differences in lake configuration, sediment P and Fe speciation, and organic content of sediments. This work demonstrates the potential utility, as well as the limitations, of P K- edge X-ray absorption near edge structure spectroscopy in determining sediment P speciation in freshwater lakes.