Dissertations / Theses on the topic 'Sols carbonatés'

L’origine de la croissance très rapide des émissions des gaz à effet de serre est attribuée, pour plus des ¾, au seul dioxyde de carbone (CO₂). Ce dernier engendre d’importants impacts sur l’équilibre thermique de la Terre, sur l’environnement et sur la biodiversité. Il est donc nécessaire de mettre en oeuvre des actions d’envergure pour réduire ces émissions. La carbonatation minérale est l’une des méthodes de la séquestration du CO₂, qui participe significativement à l’effort global de réduction des émissions d’origine anthropique dans l’atmosphère. Plusieurs auteurs ont montré que le processus de carbonatation minérale se produit naturellement en surface de la halde à résidus miniers de la mine LAB Chrysotile à Thetford Mines, Québec (Canada). L’objectif de ce projet est de trouver les évidences de la carbonatation minérale en soussurface de la halde à résidus miniers en caractérisant les phases minérales carbonatées des échantillons d’un forage de 90 m de profondeur et en identifiant les horizons présentant un fort potentiel de carbonatation minérale. Un total de 42 échantillons de forage a été prélevé à différentes profondeurs puis tamisés, broyés et analysés par les méthodes suivantes : analyseur élémentaire carbone-soufre, appareil infrarouge à transformée de Fourier-ATR, microfluorescence des rayons X et le microscope électronique à balayage. Les résultats ont montré la présence de l’artinite, la nésquehonite, la dypingite et l’hydromagnésite dans tous les échantillons analysés cela prouve que les minéraux carbonatés sont stable à l’intérieure de la pile de résidu. Cependant les minéraux ont peutêtre précipité à la surface puis avoir été subséquemment enfouis par d’autres résidus. La corrélation entre les absorbances, la teneur en carbone, les mesures de la résistivité et de la susceptibilité magnétique montre que la carbonatation minérale s'est produite d’une manière très hétérogène tout au long du forage, mais que les horizons aux profondeurs entre 15-20 m, 24-29 m, 37-42 m, 57 m, 65-69 m, 80-84 m et à 89 m ont une concentration significative en carbonates de magnésium hydratés.

Cette thèse présente un modèle thermodynamique et cinétique des interactions entre un fluide et des solutions solides idéales à plusieurs pôles. La réaction entre une solution solide et la solution aqueuse résulte de la compétition entre la dissolution stoechiométrique de la solution solide initiale et la coprécipitation de la solution solide la moins soluble dans le fluide à l'instant considéré.<br />Ce modèle a été intégré au logiciel de transport réactif en milieu poreux ARCHIMEDE, puis appliqué à divers exemples. Dans le cas de solutions solides binaires, une méthode graphique a permis de déterminer les compositions des solutions solides qui précipitent, à l'aide des potentiels chimiques des pôles.<br />Le logiciel ainsi obtenu pourrait être utilisé pour modéliser notamment la diagenèse des réservoirs pétroliers argileux ou carbonatés, ou la dispersion de polluants dans le sol.

A ocorrência de solos sódicos é comumente relacionada a regiões de clima semiárido ou condições de drenagem fechada (endorreica), e ambientes evaporativos. No Pantanal brasileiro, conhecido como a maior área inundável continental do mundo, os solos sódicos possuem significativa expressão em termos de área e funcionalidade ambiental, pela especificidade no desenvolvimento de plantas e no consumo intencional do solo por diversos animais e servindo como refúgio durante a cheia. Estes solos estão localizados nas partes mais elevadas da paisagem (paleodiques), situação diversa da maioria dos casos. Os processos pedogenéticos em solos sódicos do Pantanal Norte foram estudados na Reserva Particular do Patrimônio Natural (RPPN) SESC-Pantanal, no município de Barão de Melgaço-MT, em paleodiques de cinco setores em diferentes estádios de dissecação. Para tanto foram utilizadas descrições morfológicas em diversas escalas, datações de 14C em precipitados de carbonato e por luminescência opticamente estimulada (LOE) em sedimentos, modelagens geoquímicas e mineralógicas, análises espaciais de atributos químicos e físicos do solo, levantamento da condutividade elétrica aparente com sensor eletromagnético (EM-38) e estatísticas multivariadas. Nos solos dos setores mais conservados, foram observadas feições típicas de ambiente sedimentar lêntico, lâminas de carbonato de cálcio e ocorrência de diatomáceas, sugerindo que a formação das feições ocorreu pela concentração de águas. Esses ambientes ocorreram em condições de drenagem distintas das atuais, em que as planícies de inundação permaneciam isoladas, com limitações de drenagem lateral e vertical, promovendo a perda d\'água por evapotranspiração e consequentemente concentrando os íons em solução. A simulação da evaporação das águas dos rios São Lourenço e Cuiabá apresentaram resultados similares, indicando que ambos poderiam resultar na precipitação de calcita e saturação do Na+ no complexo de troca. Entretanto as feições observadas na morfologia do perfil como nas lâminas delgadas sugerem que os solos sódicos atualmente estão em degradação. A argiluviação é muito intensa e se destaca como principal processo de transformação desses solos, ocorrendo desde os mais conservados até em estádio mais avançado de dissecação. A ferrólise é evidente no estádio mais avançado de transformação dos solos, na transição entre E e Bt onde se estabelece uma porosidade cavitária por depleção tanto mecânica como química. Os carbonatos associados a canais, antigos poros e sem córtex definido, sugerem que as condições atuais não favorecem a sua formação. As análises mineralógicas indicam a presença de esmectita na parte mais preservada do paleodique, que nas condições atuais sofre interestratificação esmectita-caulinita. A hidrologia atual promove a erosão gradativa dos paleodiques que, anteriormente isolavam as lagoas, passando a uma drenagem mais aberta. A análise de componentes principais (ACP) identificou o processo redox como predominante na área de estudo e, em conjunto com os eventos de inundação, são os principais responsáveis pelas transformações dos solos. A via de transformação de solos nos paleodiques da RPPN SESC Pantanal foi LUVISSOLO-PLANOSSOLO. Estes últimos são muito susceptíveis ao processo de erosão promovido pela inundação e tendem a desaparecer, estreitamento a cordilheira progressivamente. A erosão acaba deixando pequenas elevações circulares denominadas de murundus, com elevados teores de Na+.<br>Sodic soils are commonly associated to semi-arid climates, closed drainage systems (endorheic) and evaporative environments. In Brazilian Pantanal, knowns as the largest continental flooded area in the earth, sodic soils have significant expression in terms of area and environmental functionality, the specificity on plants development and soil intentional consumption (geophagy) by several animals, also playing as a refuge along the flooding events. These soils are located in the higher ground of the landscape (paleodiques), different from common situation. Pedogenic processes on north Pantanal sodic soils were studied in the Private Natural Heritage Reserve (PRNP) SESC Pantanal, in Barão do Melgaço-MT, performed on \"paleodiques\" from five sectors at different dissection stages. Pedogenic process was studied by means of morphologic descriptions was done in various scales, 14C dating on carbonate precipitates and optically stimulated luminescence (OSL) in sediments, geochemical and mineralogical modeling, spatial analysis of chemical and physical properties of the soil, apparent soil electrical conductivity performed by sensor electromagnetic (EM-38) and multivariate statistics. Soil profile from more conserved sectors shows typical features of lentic sedimentation environment, calcium carbonate layer and diatoms occurrence, suggesting that the formation of these features occurred by water concentration. Current condition is the opposite from earlier, wherein the flood plains remained isolated, with limited lateral and vertical drainage promoting water loss by evaporation and therefore concentrating the ions in solution. Simulation of the evaporation of water from São Lourenço and Cuiabá rivers points out similar results, suggesting that water evaporation from both could result in calcite precipitation and Na+ saturation in exchange complex. However, the features observed in both, field morphology and thin sections suggested that sodic soils are currently in degradation. The argilluviation is very intense and stands out as the main transformation process of these soils, occurring from the most preserved even in the most advanced dissection stage of. The ferrolysis is evident in the most advanced stage processing at E and Bt transition, where it establishes a cavity porosity depletion by both mechanical and chemical. Carbonates associated with channels, old pores and channels, without a cortex, suggests the current conditions do not favor sodic soil formation. Mineralogical analyzes indicates smectite presence in the paleodique of the most preserved sector, while present conditions promotes a smectite-kaolinite interestratification. Current hydrology promotes the gradual erosion of paleodiques that previously isolated the lakes from each other, becoming a slight open drainage system. The principal component analysis (PCA) identified the redox process as major process in the study area and, along the flood events, are primarily responsible for soil transformations. Pathway of sodic soil transformation in the RPPN SESC Pantanal paleodiques was Typic Natrudalf-Glossic Natraqualf. The latter are very susceptible to erosion process, promoted by flooding and tend to disappear, narrowing the paleodique progressively. Erosion process results in smalls and circulars elevations, named mounds, with high levels of Na+.

Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2009.<br>Submitted by Albânia Cézar de Melo (albania@bce.unb.br) on 2011-02-17T13:57:37Z No. of bitstreams: 1 2009_YamileValenciaGonzalez.pdf: 14272961 bytes, checksum: 40025a2477e4b72457583ef0b6abf21a (MD5)<br>Approved for entry into archive by Guimaraes Jacqueline(jacqueline.guimaraes@bce.unb.br) on 2011-02-17T14:22:54Z (GMT) No. of bitstreams: 1 2009_YamileValenciaGonzalez.pdf: 14272961 bytes, checksum: 40025a2477e4b72457583ef0b6abf21a (MD5)<br>Made available in DSpace on 2011-02-17T14:22:54Z (GMT). No. of bitstreams: 1 2009_YamileValenciaGonzalez.pdf: 14272961 bytes, checksum: 40025a2477e4b72457583ef0b6abf21a (MD5)<br>Grande parte dos solos dos países da América do Sul são afetados por processos erosivos, sendo estes considerados como um dos problemas ambientais mais importantes dos últimos anos. Mas, são poucas as pesquisas na área de geotecnia, especificamente, no âmbito da "biotecnologia" ou "bioengenharia", que procuram, a partir da utilização de microrganismos, melhorar as propriedades geotécnicas e de estabilidade dos solos. Com esse enfoque, foi desenvolvida esta pesquisa, buscando analisar o efeito que tem a aplicação de um nutriente precipitador de carbonato de cálcio sobre a microbiota nativa na mitigação de processos erosivos um perfil de solo tropical. A metodologia usada nesta pesquisa consistiu na coleta de solo de um perfil localizado a 20m da margem da voçoroca de Santa Maria no Distrito Federal - Brasil. Em tal amostra foram identificadas as bactérias nativas e, posteriormente, determinou-se qual seria o nutriente que melhor induz a precipitação do carbonato de cálcio com essas bactérias. Posteriormente, foram caracterizadas física, química, mineralógica e mecanicamente as amostras de solo natural, para logo adicionar em blocos inalterados do solo o meio nutritivo selecionado de modo a induzir a precipitação de carbonato de cálcio. Após quinze dias de tratamento se realizaram nestes solos tratados, os mesmos ensaios de caracterização feitos nas amostras sem tratamento. Finalmente, concluiu-se que o uso do nutriente B4 interage com as bactérias do solo, precipitando carbonato de cálcio, o que causa melhoria nas propriedades físicas, químicas, mineralógicas e mecânicas dos solos estudados, mitigando, em termos gerais, os processos erosivos atuantes no perfil. Assim, a técnica de biomineralização através da precipitação de carbonato de cálcio estudada para melhorar as propriedades dos solos, demonstrou ser positiva, o que constitui um avanço na biotecnologia, pois contempla a possibilidade de reduzir o impacto ambiental e econômico causado por outras alternativas. _____________________________________________________________________________ ABSTRACT<br>Large amounts of lands in South American countries are affected by erosive processes. They have been considered one of the most significant environmental problems in the last years. However, few researches on the use of microorganisms to improve geotechnical properties and soil stability have been carried out, especially in the "biotechnology" or "bioengineering" areas. This paper aims to analyze application effects of a nutrient precipitant made of calcium carbonate on native microbiota in order to minimize erosive processes on tropical soils. The methodology consisted of collecting soil samples from an area 20 meters away from a vocoroca in Santa Maria (Distrito Federal - Brazil). Native bacteria were found in the sample and, eventually, the best nutrient to induce calcium carbonate precipitation was identified. Physical, chemical, mineral, and mechanical data from the natural soil were collected. Then, a previously selected nutritious substrate was applied in unaffected soil blocks to induce calcium carbonate precipitation. After fifteen days, soil characterization tests were accomplished in the soil blocks and in samples without any treatment. Conclusions showed that the B4 nutrient interacts with the soil bacteria, resulting in calcium carbonate precipitation. That interaction improved physical, chemical, mineral, and mechanical properties of the studied soils, minimizing active erosive processes in the samples. As a result, the biomineralization technique through calcium carbonate precipitation to improve soil properties proved to be effective. Such conclusion is a great progress in the biotechnology field, as it might reduce environmental and economic impacts caused by other techniques.

Afin de mieux comprendre et évaluer l'impact du changement climatique sur les stocks de carbone organique du sol (COS) et les flux de carbone, et en particulier la respiration hétérotrophe du sol (RS), il est nécessaire d'étudier la sensibilité de la RS à la température. Plusieurs études sur les facteurs contrôlant la dépendance de la RS à la température ont été faites antérieurement et montrent que la sensibilité de la RS à la température diminue avec la température. Ces études ont suggéré que cette diminution de sensibilité de la RS à la température était liée à la modification de la disponibilité en substrat. D'autres études ont suggéré que cette diminution est liée à l'adaptation de la communauté microbienne aux températures élevées. La sensibilité de la RS à la température est plus particulièrement critique dans les régions semi-arides, comme le Nord Ouest de la Tunisie où le stock de COS est faible. Il est nécessaire de connaître l'effet de la disponibilité en substrat sur la sensibilité de la RS à la température. Dans cette étude, les échantillons de sol ont été incubés pendant 28 jours après une période de 28 jours de pré-incubation. Les pré-incubations et incubations ont été réalisées à 20, 30, 40 et 50°C. Pour tester l'effet de la disponibilité en substrat sur la sensibilité de la RS à la température, du glucose a été ajouté au sol au début de la période d'incubation. L'analyse des résultats a montré que les températures élevées de pré-incubation réduisent la sensibilité de la RS à la température d'incubation. L'addition de glucose réduit l'effet de températures élevées de pré-incubation sur la réponse de la RS. Il apparaît ainsi que la diminution de la sensibilité de la RS après un mois de pré-incubation aux fortes températures est due à la diminution de la disponibilité en substrat. Elle semble aussi liée à une diminution de la biomasse microbienne. Puisque, le sol utilisé pour cette étude est un Cambi sol Calco-magnésimorphe, une deuxième expérimentation a été réalisée afin de déterminer la part de CO2 provenant des carbonates et la part de CO2 provenant du COS. Cette étude a été réalisée par des mesures des signatures isotopiques (δ13C) du COS, des carbonates et du CO2 émis. Après 28 jours d'incubation, 23±9% de CO2 provient des carbonates. Cette contribution est faible par rapport à la teneur initiale élevée de C-CaCO3 dans le sol (4,3%) et est indépendante de la température d'incubation. Cette étude a montré que la réduction de la sensibilité de la RS aux fortes températures est surtout liée à une réduction de la disponibilité en substrat organique et de la biomasse microbienne aux fortes températures<br>To better understand and assess the impact of climate change on the stocks of soil organic carbon (SOC) and carbon fluxes, and particularly heterotrophic soil respiration (SR), it is necessary to study the sensitivity of SR to temperature. Several studies have been achieved to improve the understanding of factors controlling the temperature dependence of SR and showed that the temperature sensitivity of SR decreases with temperature. These studies suggested that this decrease in temperature sensitivity of SR was related to change in substrate availability. Other studies presented microbial adaptation to warmed conditions. The temperature sensitivity of SR is especially critical in semi-arid regions, such as North West Tunisia, where the SOC stock is low. It is necessary to know the influence of substrate availability on the sensitivity of SR to temperature. In this study, soil samples were incubated for 28 days after a 28-day pre-incubation per iod. Pre-incubation and incubation were carried out at 20, 30, 40 and 50°C. To test the substrate availability effect on the temperature sensitivity of SR, glucose was added to soil at the beginning of the incubation period. Results showed that the highest pre-incubation temperature reduced the temperature sensitivity of SR during the subsequent incubation period. Glucose addition reduced the effect of high pre-incubation temperature on SR response. Thus, it appears that the observed decrease in SR sensitivity to temperature after one month pre-incubation at high temperature was due to a reduce in substrate availability and to a decrease in microbial biomass. Since the soil used in this study is a Calcari-Leptic Cambisol, a second experiment was also performed to determine the amount of CO2 from carbonates and the amount of CO2 from SOC. This study was carried out by measurements of the isotopic signatures (δ13C) of SOC, carbonates and emitted CO2. After 28 days of inc ubation, 23±9% of CO2 came from carbonates. This contribution was low compared to the high initial C-CaCO3 content in soil (4.3%), and it was independent to the incubation temperature. This study showed that reduce in the sensitivity of SR to high temperatures was probably due to a reduction in the substrate availability and to a decrease in microbial biomass

Dans les pays à fort risque sismique, les fondations bâties sur un sous-sol trop meuble peuvent avoir des conséquences désastreuses. En effet, dans certain cas, les mouvements sismiques provoquent des tassements, en particulier lorsque les sous-sols granulaires sont saturés en eau. Ce phénomène dit de liquéfaction ou perte de la résistance des sols, résulte de la montée de la pression interstitielle de l'eau lorsque les vibrations sismiques tendent à tasser les grains les uns contre les autres. Pour éviter l'effondrement des édifices, le génie civil renforce la résistance mécanique des terrains plus ou moins perméables, en procédant à des injections de matériaux par le biais de forages. Afin d'améliorer les procédés de consolidation des sols, une nouvelle technique compte apporter une réponse en utilisant des cristaux de carbonate de calcium précipités in situ par voie microbiologique. La précipitation bactérienne du carbonate de calcium peut s'accomplir par l'hydrolyse de l'urée, via l'enzyme uréase. Ceci conduit à l'alcalinisation du micro environnement, permettant la précipitation d'ions carbonates en présence d'ions calcium. Sporosarcina pasteurii a été choisi car c'est un micro-organisme alcalinophile, non pathogène et détenteur de concentration intracellulaire élevée en uréase. L'objectif était d'utiliser industriellement ce micro-organisme pour son pouvoir calcifiant, afin d'améliorer la cohésion des grains de sol, en milieu saturé, sans en obturer la porosité. Trois axes de recherche menés conjointement, ont été définis pour ce travail de préindustrialisation du procédé de bio consolidation in situ. Le premier axe a été l'obtention d'un milieu de production de biomasse, industriel, permettant de stabiliser l'accession aux fortes activités enzymatiques. Cette étape est indispensable du fait des exigences d'application du procédé sur le chantier, éloignées des conditions physiologiques de la bactérie S. pasteurii. Il a été vital de décoder les modalités et la composition d'un milieu de culture industriel propre à favoriser la production de S. pasteurii et d'uréase. Ce travail a établi les principaux paramètres de suivi de culture et leur signification physiologique. Il a permis d'étudier la régulation de la synthèse de l'enzyme uréase et de proposer un modèle de régulation chez S. pasteurii. Le second aspect de recherche s'est attaché à créer une solution calcifiante à partir d'un mélange d'urée et de sel de calcium. Des colonnes de sable fin ont été utilisées pour évaluer l'impact, sur la bio calcification, de deux sources de sel de calcium, le nitrate et le chlorure de calcium. Les résultats mettent en avant, l'existence d'une réduction de la vitesse d'hydrolyse en présence d'ion calcium et l'absence de différence significative de résistance à la compression (RC) entre les deux sels. D'autre part, lorsque les activités enzymatiques d'hydrolyse sont moindres, le processus de bio calcification, paraît plus stable et efficace. De nombreuses images au microscope électronique à balayage (MEB) ont confirmé ces résultats. Enfin, une amélioration du procédé vient de la proposition d'une solution calcifiante, additionnée de très faibles quantités de matière organique, afin de favoriser l'élongation des cristaux de carbonate de calcium dans les zones inter-granulaires. Le troisième axe a été la mise en place pour une application en chantier, d'un protocole d'injection en colonne de sable fin d'une suspension de biomasse suivie d'une solution calcifiante. Ces travaux ont permis d'identifier, une corrélation entre les zones de dépôt de biomasse et les portions de sable consolidés, ainsi que les principaux facteurs responsables de l'hétérogénéité de la bio calcification. La densité cellulaire et la granulométrie bactérienne définissent par filtration mécanique et physicochimique un premier profil de distribution de la biomasse en milieu poreux. En fonction du niveau d'activité enzymatique et de la qualité de la suspension bactérienne injectée, la solution calcifiante interagit en précipitant sous forme de flocs et en amenant un changement local de viscosité. Pendant l'injection, l'écoulement des fluides redéfinit le premier profil de biomasse par un lessivage au sein du système poreux. La granulométrie du sable et la vitesse d'injection influencent également le lessivage. Grâce à ces travaux, l'hétérogénéité de la bio-calcification a été diminuée en intégrant dans le protocole d'injection, des temps d'arrêt d'injection pour l'immobilisation des fluides.

La dépollution des sols et le choix des méthodes adéquates pour cette application ont suscité un intérêt particulier ces dernières années. Il existe presque autant de méthodes de dépollution que de type de pollution. La méthode de dépollution par électrocinétique est l’une de ces méthodes. Elle consiste à appliquer un courant électrique et de provoquer ainsi la migration des polluants. L’objectif de ce travail est l’étude du comportement d’une kaolinite, d’un mélange de kaolinite et de carbonate en présence de plomb sous l’effet d’un traitement électrocinétique et d’étudier l’évolution de la structure de la kaolinite et des mélanges kaolinite-carbonate avant et après l’électrocinétique. Pour cette étude, la longueur de l'échantillon était de 20 cm. Le champ électriqueappliqué est égale à 1V/cm. Les essais de traitement électrocinétique sont réalisés à des durés égales à 48h, 72h, 96h, 120h, 168h, 192h. Des mesures sont effectués au cours des essais, telle que, le pH des réservoirs anodiques et cathodique, l’intensité de courant électrique, la différence de potentiel de l’échantillon et le flux électro-osmotique. Les mesures effectuées après les essais sont, le pH, la conductivité en fonction de la distance par rapport à l’anode. Ainsi que des mesures par, diffraction des rayons X, porosimétrie au mercure et surface spécifique sont également réalisées pour étudier l’évolution de la structure après le traitement électrocinétique<br>Soil remediation and the selection of appropriate methods for this application have attracted special interest in recent years. There are almost as many methods of remediation that type of pollution. Method of depollution by electrokinetic is one of these methods. It consists in applying an electric current and to thereby cause the migration of pollutants. The objective of this work is to study the behavior of kaolinite, a mixture of kaolinite and carbonate of lead under the effect of an electrokinetic treatment and to study the evolution of the structure kaolinite, and kaolinite-carbonate mixtures before and after the electrokinetic. For this study, the sample length was 20 cm. The applied electric field is equal to 1V / cm. Electrokinetic treatment trials are made equal to 48h, 72h, 96h, 120h, 168h, and 192h. Measurements are made during the tests, such as the pH of the anodic and cathodic reservoirs, the intensity of electric current, the potential difference of the sample and the electro-osmotic flow. The measurements performed after the tests are the pH, the conductivity as a function ofthe distance from the anode. And measures by, X-ray diffraction, mercury porosimetry and surface area are also performed to study the evolution of the structure after the electrokinetic treatment

Uma característica de destaque da Nhecolândia, uma sub-região do Pantanal Sul-Mato- Grossense, é a presença de lagoas doces (baías) e salgadas (salinas) com uma grande variabilidade química entre si. Apesar da presença de sal nas salinas ser historicamente atribuída a processos passados, estudos recentes sugerem que as águas salgadas estão sendo originadas atualmente devido à concentração por evaporação. O perfil químico das águas salinas estaria sendo originado principalmente pelo controle de elementos (Ca2+, Mg2+ e Si(OH)4) durante a concentração das águas, com o conseqüente envolvimento destes íons em dois processos: a formação de carbonatos e de silicatos magnesianos. Estudos preliminares em solos de salinas sugerem que a ocorrência de nódulos esbranquiçados e a presença de um horizonte enriquecido em argila podem evidenciar estes dois processos. Neste tipo de ambiente, carbonatos como calcita e dolomita são comumente neoformados, mas há divergências na literatura quanto ao mecanismo de origem autigênica dos silicatos magnesianos. Baseando-se no exposto acima, foram definidos os seguintes objetivos para a presente pesquisa: 1) ampliar o conhecimento sobre os solos associados às salinas através de uma caracterização baseada em dados de campo e laboratório dos solos presentes no entorno de uma lagoa salina representativa da Nhecolândia (lagoa do Meio); 2) identificar os processos envolvidos no controle do Ca2+, Mg2+ e Si(OH)4 nas águas salinas, através do estudo das relações entre as fases líquidas (águas superficiais e subsuperficiais) e sólidas (minerais) presentes nos solos do entorno da lagoa do Meio; e 3) identificar os mecanismos específicos de gênese dos minerais autigênicos possivelmente presentes nos solos do entorno da lagoa do Meio. As amostras de solo foram coletadas ao longo de uma topossequência nos arredores da lagoa do Meio e submetidas à análise granulométrica, análises químicas (ICP-MS, pH, CE, carbono total, carbonato de cálcio equivalente, bases trocáveis e testes de imersão em água, ácido e bases) e análises mineralógicas (DRX, MET-EDS). Amostras de água superficiais e subsuperficiais foram coletadas em um transecto que abarca a topossequência estudada e então encaminhadas às análises de pH, Eh, CE, temperatura, titulação com HCl, cromatografia de íons, EAA e ICP-MS. Os solos dos arredores da salina do Meio caracterizam-se pela textura areia a franco-arenosa, pela ausência de estrutura e, de maneira geral, por altos valores de pH, CE, CTC e saturação em Na+. O pH fortemente alcalino e o domínio de Na+ no complexo de troca desencadeiam a atuação do processo de solonização e dos seguintes processos específicos associados: migração de matéria orgânica perfil abaixo, precipitação de carbonatos (calcita, dolomita e nahcolita) em nódulos, solubilização/precipitação de sílica amorfa e formação autigênica de minerais de argila do grupo das esmectitas e micas. Diferentes esmectitas estão presentes ao longo da topossequência: a) na zona raramente atingida pelas variações sazonais do nível d\'água da salina, a esmectita é do tipo ferribeidelita, possui um grau de interestratificação com mica e vermiculita e apresenta teores de Fe3+ similares às micas identificadas no mesmo solo. Estas características sugerem que o mineral do tipo ferribeidelita é originado pela transformação de micas enriquecidas em Fe3+, sendo a vermiculita provavelmente uma fase intermediária nesta transformação; b) na zona de maior variação sazonal do nível d\'água da salina, as esmectitas são classificadas como do tipo saponita e estevensita. Os baixos teores de elementos terras-raras nas amostras enriquecidas nestes minerais, o controle do Mg2+ e do Si(OH)4 nas águas próximas à lagoa do Meio, a saturação das águas do entorno da lagoa em relação a saponita e estevensita e a presença destas esmectitas magnesianas nos locais onde são esperadas máximas taxas de evaporação, provam que estes minerais estão se originando por precipitação química diretamente da coluna d\'água da lagoa salina. Já as micas presentes nos solos estudados são do tipo ilita, glauconita e mica glauconítica, possuem interestratificação com camadas de esmectitas e parecem estar associadas a materiais amorfos. Experimentos de síntese disponíveis na literatura mostram que águas semelhantes às associadas à lagoa do Meio são ideais para a cristalização de micas a partir da precipitação inicial de hidróxidos amorfos. Desta forma, as evidências obtidas sugerem que estas micas são neoformadas a partir da precipitação inicial de amorfos e posterior cristalização. Os resultados obtidos certamente ampliaram o conhecimento sobre os solos presentes no entorno de lagoas salinas, uma vez os estudos disponíveis na literatura são baseados quase que exclusivamente em dados de campo. Mostrou-se que o controle do Ca2+ das águas mais salinas está sendo realizado pela formação de calcita e dolomita em nódulos, enquanto o controle do Mg2+ e do Si(OH)4 está ocorrendo pela formação de esmectitas magnesianas do tipo saponita e estevensita. Estes processos são provavelmente os responsáveis pela alta variabilidade entre as águas doces das baías/vazantes e as salgadas das salinas/arredores, conforme hipótese lançada em literatura. Assim, o presente trabalho fornece fortes evidências de que a presença de sal nas águas das lagoas salinas da Nhecolândia é atual ou, ao menos, tem contribuição de processos atuais. Por fim, mostrou-se ser possível a formação conjunta de ilita, glauconita e mica glauconítica e de esmectitas do tipo saponita e estevensita pelo mecanismo de precipitação diretamente das águas ou soluções em ambientes sujeitos a concentração evaporativa.<br>A distinctive feature of Nhecolândia, a sub-region of the Pantanal wetland, is the presence in close proximity of freshwater and saline lakes with a huge chemical variability. The salt has been generally attributed to Pleistocene processes, but recent studies have suggested that saline waters arise from present-day concentration of freshwater by evaporation. The chemical profile of saline waters would be originated by chemical control of Ca2+, Mg2+, and Si(OH)4 as the water becomes more saline. Two processes would be responsible for this control: formation of carbonates and formation of Mg-silicates. The presence of whitish nodules and clayey horizons in soils associated to the saline lakes would be evidences of these processes. In saline-alkaline environments, carbonates such as calcite and dolomite are commonly formed by chemical precipitation, but the mechanisms responsible for Mgsilicates genesis are still under debate. The objectives of this research are: a) increasing the general knowledge about soils associated to Pantanal saline lakes through a detailed characterization of the soils located around a representative saline lake of Nhecolândia (\"Salina do Meio\"); b) identifying the processes involved in Ca2+, Mg2+ and Si(OH)4 control from saline waters, through the study of relationships between waters and minerals present in the soils around \"Salina do Meio\"; c) identifying the specific mechanisms of authigenic genesis of the minerals possibly found around \"Salina do Meio\". Soils were sampling along a toposequence and submitted to physical (particle-size), chemical (ICP-MS, pH, EC, total carbon, inorganic carbonate, exchangeable bases, and soaking in H2O, HCl 1N, and NaOH 4M), and mineralogical analyses (XRD and TEM-EDS). Water was collected along a transect involving the lake and submitted to pH, Eh, EC, temperature, titration with HCl, ion chromatography, and ICP-MS analyses. The studied soils are sandy, structureless, and present, in general, high values of pH, CE, CEC, and Na+ saturation. Prevailing of Na+ in the waters and exchangeable sites and dominance of extremely high pH strongly suggest the general action of solonization in these soils and its influence on the following processes: organic matter translocation toward deeper horizons, precipitation of carbonates (calcite, dolomite, and nahcolite) in nodules, precipitation of amorphous silica, and authigenic formation of smectites and micas. Different authigenic smectites occur along the toposequence: a) in the zone hardly reached by the lake level variation, the smectite is classified as ferribeidellite-type, present an interstratification with mica and vermiculite, and has similar amounts of Fe3+ than the Fe-mica present in the soils. These characteristics suggest that this ferribeidellite-type mineral originates from transformation of Fe-mica and that vermiculite may be an intermediate phase in this transformation; b) in the zone of seasonal lake level variation, the smectites are classified as saponite- and stevensite-type minerals. Low REE amounts in the samples enriched in saponite and stevensite, geochemical control of Mg2+ and Si(OH)4, saturation with respect to Mg smectite in the more saline waters, and presence of Mg-smectite where the maximum of evaporation is expected, prove that saponite- and stevensite-like minerals originate by chemical precipitation from the water column of the saline lake. The micas present in the studied soils are classified as illite-, glauconite- and glauconitic mica-type minerals. They present 20% or less smectite layers and seem to be associated to amorphous materials. Synthesis of micas available in the literature shows that water conditions similar to the study area allow for dioctahedral mica crystallization from initial precipitation of amorphous hydroxides. Therefore, it suggests that micas of study area are neoformed. The results of this dissertation contributed to a better understanding about the soils associated to Nhecolândia saline lakes, since most of the published researches are based on field data. The control of Ca2+ from more saline waters occurs by formation of calcite and dolomite in nodules, while the control of Mg2+ and Si(OH)4 occur by formation of Mg-smectites classified as saponite- and stevensite-type. These processes are probably responsible for the chemical variability between freshwater and saline lakes, as supposed in a previous research. Therefore, the present work gives strong evidences about the current origin of Nhecolândia salt water. Also, it showed the possibility of genesis of illite, glauconita, glauconitic mica, saponite, and stevensite minerals through direct precipitation of waters or soil solutions under concentration by evaporation.

Over half of the carbon (C) taking part in the global C cycle is held in terrestrial systems. Because of the sensitivity of the C cycle to changes in such soil-based pools of carbon, it is important to understand the basic mechanisms by which soil C is stored and cycled between the range of di erent pools which occur belowground. In the context of climate change mitigation, it is considered that increasing soil-based stocks of C, either by reducing losses from soils, or by actively sequestering new carbon, is a potentially important strategy . Organic carbon is the main form of carbon in soil and as such has received most focus. Cont/d.

The factors which affect the engineering properties of calcium carbonate cemented soil are examined. The influence of calcium carbonate content, molding moisture content, and confining pressure on the strength characteristics of two types of soil is investigated in two distinct phases of the research. Type A soil, obtained from the University of Arizona Campbell Avenue Farm in Tucson, was used for the artificially cemented specimen stage. It is composed of sand and silt-size particles with some clay and is virtually free of calcium carbonate in its natural state. Sierrita soil, obtained from the Twin Buttes Open Pit Mine south of Tucson, was used for the reconstituted sample stage. It is naturally cemented with calcium carbonate and is composed mainly of sand, gravel, a small amount of silt, and occasional large-sized (boulder and cobble) particles. Specimens for triaxial compression testing were compacted for each phase of the study under carefully controlled conditions. Three test series were carried out on Type A soil artificially cemented with calcium carbonate. Three percentages (0%, 15%, and 30%) on a dry weight basis of the soil were used. Two molding water contents, one dry and one wet of optimum moisture content, were established for each test series. Unconsolidated undrained triaxial compression tests were carried out on oven-dried specimens at three different confining pressures to obtain shear strength parameters. The fabric characteristics of selected specimens were then defined by viewing them under a scanning electron microscope. The results indicate that the strength of the calcium carbonate cemented soil depends on the distribution and not necessarily the content of the cementing agent within the soil mass. Visual examination of the various microstructures of the artificially cemented soil confirmed the hypothesis that strength gain occurs when the calcium carbonate particles are concentrated at the points of contact between soil grains. Visual examination of the fabric of the naturally cemented Sierrita soil showed the microstructure to be highly compressed with weathered calcium carbonate particles dominating the soil structure. The calcium carbonate content was found to range from 14 to 23%. Because of sampling difficulties, an in situ cohesion value for the Sierrita soil could not be obtained from conventional laboratory tests. Therefore, the value was obtained by back analysis of the stability of actual slopes existing at Twin Buttes Mine. Slope stability analyses using Bishop's Modified Method with a search routine based on the Simplex Method of Nelder and Mead were performed. Stability analyses were also performed using strength properties of artificially cemented Type A soil. These analyses showed the relationships among cohesion, friction angle, safety factor, and calcium carbonate content for a specified slope geometry.

Ce mémoire est consacré à la description du comportement de retrait-gonflement des sols. Il analyse l’effet de plusieurs paramètres qui devraient être pris en compte dans la classification des sols pour le retrait et gonflement, tels que la densité, la teneur en carbonates et le nombre de cycles de séchage-humidification subis par le sol. Pour étudier le retrait volumique, un appareil automatisé a été développé au LCPC, pour mesurer simultanément les changements de volume du sol et les pertes d’eau lors du séchage. Des essais de retrait libre à l’air et de gonflement libre à l’œdomètre ont été réalisés sur différents types de marnes et d’argiles. Les essais montrent une différence de comportement entre les marnes et les argiles. Leur comportement hydrique et mécanique a été expliqué en partie grâce aux résultats des essais de porosimétrie au mercure et aux observations de la microstructure des sols réalisées au microscope électronique à balayage environnemental. Enfin une méthodologie est proposée pour mesurer la sensibilité d’un sol au retrait-gonflement (son amplitude de déformation) à partir d’essais simples, peu coûteux et rapides.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-05-17T16:02:30Z No. of bitstreams: 2 texto completo.pdf: 4397118 bytes, checksum: 24d763221de6830777875f4047513d1b (MD5) anexo pag 177.pdf: 7946632 bytes, checksum: 6b73ff584c880427a78257872f71e85b (MD5)<br>Made available in DSpace on 2017-05-17T16:02:30Z (GMT). No. of bitstreams: 2 texto completo.pdf: 4397118 bytes, checksum: 24d763221de6830777875f4047513d1b (MD5) anexo pag 177.pdf: 7946632 bytes, checksum: 6b73ff584c880427a78257872f71e85b (MD5) Previous issue date: 2015-08-31<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico<br>Com o objetivo de avaliar a pedogênese em ambiente tropical sob influência de rochas carbonáticas, selecionou-se uma área entre o norte do Estado do Rio de Janeiro e o Sul do Estado do Espírito santo, onde são comuns os afloramentos de mármores e calcários. A relação solo-relevo foi avaliada em uma microbacia hidrográfica através de suas características pedomorfométricas. A pedogênese foi avaliada por meio das características físicas, químicas, mineralógicas e micromorfológicas de perfis de Cambissolos Háplicos e Argissolos Vermelhos, derivados de calcário, anfibolito e gnaisse. A geoquímica foi avaliada em perfis de Argissolo Vermelho, Chernossolo Háplico e Chernossolos Rêndzicos, derivados de anfbolito e calcário. Os principais resultados encontrados foram: (i) a altitude foi o atributo topográfico mais correlacionado com as características físicas e químicas dos solos da microbacia Córrego Duas Barras; (ii) os Cambissolos Háplicos e Argissolos Vermelhos, derivados de calcário, anfibolito e gnaisse, são bem drenados, pouco profundos, vermelhos, bem estruturados, argilosos, moderadamente ácidos a praticamente neutros, eutróficos, não carbonáticos e com atividade da fração argila variando de moderadamente baixa a média. Possuem traços de minerais alteráveis, como feldspatos, hornblenda, talco e minerais 2:1, resultado de um processo de intemperismo moderado, onde a remoção da sílica liberada dos minerais não atingiu níveis elevados; (iii) a argiluviação não demonstra ser o processo pedogenético mais expressivo na formação do gradiente textural dos Argissolos; (iv) os solos desenvolvidos de calcário, por estarem em local de drenagem desimpedida não apresentam o processo de carbonatação, ao passo que seus valores de pH mais elevados facilitam a ferruginização, formando solos mais vermelhos, com maiores teores de óxidos de ferro, cujos valores da substituição isomórfica de Fe por Al são característicos da hematita; (v) fração argila dos Cambissolos Háplicos e Argissolos Vermelhos, derivados de calcário, anfibolito e gnaisse, é predominantemente caulinítica, e apresenta traços de esmectitas e cloritas, com possibilidade de hidroxi nas entrecamadas; (vi) as caulinitas são pouco espessas, com superfície específica média maior do que as geralmente observadas para este mineral; (vii) a LMA001 da caulinita foi menor na argila tratada com DCB, e maior nos solos derivados de calcário; (viii) o índice de cristalinidade da caulinita foi ligeiramente maior na fração argila grossa dos Cambissolos Háplicos e Argissolos Vermelhos; (ix) os principais processos pedogenéticos dos Chernossolos foram a lixiviação no horizonte superficial, a formação de argila no horizonte textural, e a calcificação nos horizontes sub superficiais; (x) a MOS apresenta depleção nos valores δ13C com o aumento da profundidade e enriquecimento com o aumento do teor de COT nos Chernossolos; (xi) os solos apresentam dois padrões diferentes de distribuição de δ15N em profundidade: enriquecimento com o aumento da profundidade para o solo não-carbonático; e depleção com o aumento da profundidade para os solos carbonáticos; (xii) a idade 14C da MOS variou de 295 a 7190 anos BP entre a superfície e a sub superfície, respectivamente; (xiii) não foram observadas diferenças isotópicas significativas para os valores de δ18O e δ13C entre os carbonatos do solo e dos nódulos carbonáticos; (xiv) os valores 14C dos nódulos carbonáticos revelaram idade Pleistocênica; (xv) os valores de δ13C dos nódulos carbonáticos apresentaram maior equilíbrio isotópico com a vegetação do que com atmosfera; (xvi) os valores médios de δ18O entre a borda e o núcleo sugerem que a precipitação dos nódulos carbonáticos, ao longo do tempo, ocorre provavelmente sempre na mesma estação.<br>Aiming to evaluate the pedogenesis in tropical environment under the influence of carbonate rocks, was selected an area between the northern of the State of Rio de Janeiro and south of the State of Espirito Santo, where marble and limestone are abundant. The soil-relief relationship was evaluated in a watershed through its pedomorphometric features. The pedogenesis was evaluated by the physical, chemical, mineralogical and micromorphological characteristics of Inceptsols and Ultisols derived from marble, amphibolite and gneiss. The geochemistry was evaluated in Mollisols derived from amphibolite and marble. The main results were: (i) the elevation was the topographic attribute more correlated with the physical and chemical soil characteristics of the watershed Córrego Duas Barras; (ii) Inceptsols and Ultisols, derived of marble, amphibolite and gneiss, are well drained, shallow, red, well structured, clayey, moderately acidic to slightly alkaline, eutrophic, carbonate free, and clay activity ranging from moderately low to medium. They have traces of labile minerals such as feldspars, hornblende, talc and 2:1 minerals, result of a moderate weathering process, where the removal of silica released from minerals has not reached a high level; (iii) the argilluviation is not the most significant pedogenic process to formation of textural gradient in the Ultisols; (iv) the soils developed from marble, because they are in unobstructed drainage site does not have the carbonation process, while its higher pH values facilitating ferruginization forming more redness soils, with higher iron oxide contents, whose the values of isomorphic substitution Fe by Al are characteristic of hematite; (v) the clay fraction of Inceptsols and Ultisols derived from limestone, amphibolite and gneiss, is predominantly kaolinite, and shows traces of smectite and chlorite, with the possibility of hydroxy interlayer; (vi) the kaolinite are thin, with an specific surface higher than usually observed for this mineral; (vii) the LMA001 of kaolinite was lower in the clay treated with DCB, and higher in soils derived of marble; (viii) the kaolinite index of crystallinity was slightly higher in the coarse clay of Inceptsols and Ultisols; (ix) the main pedogenic processes of Mollisols consist of leaching in the surface horizons, formation of clay in the textural horizon, and calcification in the sub surface horizons; (x) the SOM shows a depletion in δ13C values with increasing depth and enrichment with increasing TOC content in the Mollisols; (xi) the soils have two different patterns of δ15N distribution in depth: enrichment with increasing depth to the carbonate-free soil; and depletion with increasing depth to the carbonatic soils; (xii) the 14 C age of SOM ranged 295-7190 y BP, between the surface and the sub surface, respectively; (xiii) there were no significant differences for δ18O and δ13C values between the soil carbonates and nodules carbonates; (xiv) the 14 C values of carbonate nodules revealed Pleistocene age; (xv) the δ13C values of carbonate nodules presented greater isotopic equilibrium with vegetation than with atmosphere; (xvi) the average values of δ18O between the edge and the core suggest that precipitation of carbonate nodules, over the time, probably occurs always in the same season.<br>Foi publicado um anexo junto com o texto completo.

L’analyse de la morphobathymétrie, de la réflectivité acoustique et de la sismique haute et très haute résolution des données acquises lors des campagnes océanographiques Carambar (2010 – 2017) a permis d’obtenir une vue d'ensemble de la morphologie et des processus de transferts sédimentaires, de la pente supérieure à la plaine abyssale d'un système carbonaté moderne : la pente nord-est du Little Bahama Bank (LBB). Ces travaux viennent compléter les résultats de Tournadour (2015), Chabaud (2016), et Fauquembergue (2018), notamment sur l’architecture profonde de ce système. La distribution spatiale des échofaciès et des faciès de réflectivité acoustique montrent une grande variété de structures, témoignant de l’activité de nombreux processus sédimentaires le long de la pente du LBB. Elle montre notamment l’existence d’une subsidence différentielle entre la partie orientale et occidentale du LBB. Les profils sismiques haute-résolution fournissent de nouveaux indices sur l'origine du Great Abaco Canyon, canyon carbonaté d'une profondeur inhabituelle. Des failles de direction N110, apparentées à la Great Abaco Fracture Zone, indiquent un contrôle structural sur l'emplacement du Great Abaco Canyon et sa physiographie actuelle. Ces structures suggèrent une réactivation néogène du réseau de failles pendant la croissance de la plate-forme, contrastant avec le calme tectonique apparent de la région décrit jusqu’alors. Le complexe chenal-lobe, sans expression bathymétrique, à l’embouchure du Great Abaco Canyon, montre qu’une période exceptionnelle d'exports gravitaires a largement contribué à l’activité du canyon au Miocène supérieur. L'architecture sismique du Blake Plateau montre une succession de faciès sismiques bien définis, séparés par des réflexions de grande amplitude interprétées comme des drifts contouritiques. La morphologie de ces drifts souligne l'apparition d'un courant oligo-miocène, s'écoulant vers le nord le long du bord du Blake Bahama Escarpment et à travers le Blake Plateau. Des monts carbonatés d’eaux froides, associés soit aux échappements de fluides, soit aux courants situés dans les paléo-dépressions topographiques, permettent de définir deux origines pour ces monts : les bioherms (type 1 &amp; 2) et les chemoherms (type 3). L'association stratigraphique des monts avec les surfaces d'érosion est révélatrice des changements à grande échelle des courants de fond dans la zone<br>The large acoustic data set acquired during the Carambar cruises (2010 – 2017) is composed of high resolution bathymetry, backscatter data and very-high resolution seismic lines which allow for an overview of the morphology and sediment transfer processes from the shallow upper slope to the abyssal plain of a modern carbonate system: the north-eastern slope of the Little Bahama Bank. This work completes the results from Tournadour (2015), Chabaud (2016), and Fauquembergue (2018), with a focus on the architecture of this deep system. Surficial distribution of the acoustic facies and echofacies reflects a wide variety of sedimentary processes along and across the slope. It demonstrates the occurrence of a differential subsidence affecting the eastern versus western part of the bank. High resolution seismic profiles give new clues on the origin of a giant carbonate canyon, the Great Abaco Canyon. N110-trending faults have been recognized on the seismic profiles crossing through the Great Abaco Canyon mouth and can be related to the Great Abaco fracture zone. These structures suggest a Neogene fault reactivation during platform growth, contrasting with the quiet tectonic period previously described on the region. The channel – lobe complex at the Great Abaco Canyon mouth has no bathymetric expression. It shows that exceptional mass-flow events largely contributed to an important sediment transfer in the canyon during the Upper Miocene. The seismic architecture of the southern part of the Blake Plateau shows a succession of well-defined seismic facies, separated by high-amplitude reflections, interpreted as stacked contouritic sequences. These contouritic drifts emphasize the occurrence of an Oligo-Miocene current flowing northward along the Blake Bahama Escarpment edges and across the Blake Plateau. Fluid-associated structures and current-associated mounds located in topographic lows allow the definition of two origins for mounds: bioherms (type 1 &amp; 2) and chemoherms (type 3). The stratigraphic association of mounds with erosion surfaces is further indicative of large-scale changes of the activity of bottom currents in the zone

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-08-01T13:15:14Z No. of bitstreams: 1 Iran Neves Ordonio.pdf: 868102 bytes, checksum: 02c9599adf76f389980e6006cdfb959a (MD5)<br>Made available in DSpace on 2016-08-01T13:16:57Z (GMT). No. of bitstreams: 1 Iran Neves Ordonio.pdf: 868102 bytes, checksum: 02c9599adf76f389980e6006cdfb959a (MD5) Previous issue date: 2004-12-29<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES<br>Samples of the surface and B horizons of a Plintosol as well as the B horizon of a Nitosol were treated with calcium carbonate, calcium and magnesium carbonate, and calcium sulfate. The objective was to study the effects of such amendments on chemical and physical properties of the soils. The experiment was carried out in a completely randomized design with three replicates. The samples were packed into PVC columns sectioned in two 15 cm-cylinders. The amendments were applied on the upper cylinder. The lime requirement was calculated to reach 60% of base saturation while the gypsum dose was equivalent to 25% of lime requirement. Soil samples were kept incubated for 36 days. During this period, they were leached out through two pore-volumes using deionized water. The results showed that the treatments were not effective at ameliorating the soil acidic condition. There was not a significant influence of the amendments on the cation movement in the soil column as corroborated by low cation concentrations in the lower cylinder. On the other hand, calcium carbonate and its application with calcium sulphate provoked highest Ca contents in the lower cylinder. Calcium and magnesium carbonate treatments as well as their association with calcium sulphate provided the highest Mg concentrations in lower cylinders. This resultshows the role of such chemical amendments in supplying Ca and Mg to subsurfacee layers of soil. The treatments did not alter the physical soil properties. Water dispersed clay and floculation were little influenced by treatments, especially for the B horizons, which were statistically equal.<br>Amostras de Plintossolo horizonte Ap, Plintossolo horizonte Bt e Nitossolo horizonte B1 foram utilizadas no estudo, com o objetivo de avaliar o uso de carbonato de cálcio, carbonato de cálcio e magnésio, sulfato de cálcio e associação entre eles, investigando suas interações nas alterações químicas e físicas. O experimento foi realizado em delineamento inteiramente casualizado, com quatro repetições. As amostras de solos foram acondicionadas em colunas de PVC com 10 cm de diâmetro e 30 cm de altura, seccionados em dois cilindros de 15 cm. Nos cilindros superiores foram aplicados os corretivos. A necessidade de calagem foi calculada de modo a elevar a saturação por bases a 60 %, e a dose de sulfato de cálcio correspondente a 25 % da necessidade de calagem de cada amostra de solo. O período de incubação foi de 36 dias, durante o qual as amostras foram lixiviadas com dois volumes de poros com água deionizada, em aplicações semanais. Após esse período, procederam-se às avaliações físicas e químicas dos solos e químicas do material lixiviado. Os resultados obtidos indicaram que não houve correção de forma efetiva quando as propriedades químicas após o período de incubação. Houve pequena influência das doses aplicadas quanto à movimentação de cátions em profundidade, evidenciado pela pequena concentração de cátions no cilindro inferior. Entretanto, no cilindro inferior, maiores teores de cálcio foram relacionados aos tratamentos contendo carbonato de cálcio (CC) e sua combinação com sulfato de cálcio (CCG). Os tratamentos contendo carbonato de cálcio e magnésio (CM) e sua combinação com sulfato de cálcio (CMG), proporcionaram, por sua vez, maiores teores de magnésio nas referidas camadas. Esse fato evidencia a contribuição do carbonato de cálcio e carbonato de cálcio e magnésio no fornecimento de Ca e Mg e o efeito do sulfato de cálcio em profundidade. Os tratamentos de correção aplicados não proporcionaram diferenças nas propriedades físicas entre os cilindros. Após a aplicação dos tratamentos percebe-se um efeito pouco expressivo de argila dispersa em água e do grau de floculação, principalmente para as amostras doPlintossolo Horizonte Bt e o Nitossolo Horizonte Bt, cujas diferenças não foram significativas.

Le stockage des déchets en site de décharge peut engendrer de nombreux problèmes, notamment celui de la pollution du sous-sol. Celle-ci devient de plus en plus aiguë en présence de nappe phréatique. En effet, des matières solubles sont entraînées par l'eau et percolent dans les couches inférieures du sol. Le but de cette étude est donc de trouver des solutions destinées à réduire le flux de pollution en diminuant le coefficient de perméabilité d'un sol naturel dans l'optique du traitement du fond, des flancs et de la couverture des centres d'enfouissement techniques La perméabilité d'un sol naturel dans l'optique du traitement du fond, des flancs et de la couverture des centres d'enfouissement techniques. La perméabilité d'un sol étant liée à l'importance et à la disposition des vides qu'il contient, nous réduirons des vides et donc la perméabilité, par correction granulométrique puis compactage du mélange. A partir de matériaux naturels perméables pouvant être aisément remaniés (sable, craie), nous avons recherché, en laboratoire, les conditions optimales de traitement de ces sols par ajouts d'argiles puis compactage de traitement conférant au mélange un faible coefficient de perméabilité (10-9m/s par exemple)<br>The direct landfill of waste can generate several problems, particularly those of ground-water pollution. Indeed, soluble substances are driven by water and percolate through soil layers. The aim of this study is then to find solution up tu reduce the flow of pollution by a decrease of hydraulic conductivity of a natural soil, in order to achieve treatment of landfill bottom, flanks and cover systems. The permeability of a given soil is related to volume and distribution porosity within the soil. We first reduce these voids and so the permeability, by granulometric correction and compaction of the mixture. From natural previous soils which can be easily re-handled (sand and chalk), we have tried to obtain, in laboratory, the optimum conditions of treatment of these soils by admixture of clays and compaction which confers to the mixture a low permeability (10-9m/s for example)

Dans le sol, les racines absorbent des ions mineraux qu'elles transportent vers les parties aeriennes, ou qu'elles accumulent dans leur cortex. Il arrive que ces ions y cristallisent. Les structures rhizomorphes calcaires sont des vestiges de racines calcifiees, dont l'organisation est analogue a celle des microdiums. Elles se developpent dans de nombreux sols calcaires. L'analyse de leur organisation nous amene a emettre l'hypothese que leur formation resulte d'une redistribution sur place du caco::(3) du sol consecutive a l'absorption et a l'accumulation de ca**(2+) par les racines. Cette hypothese est confirmee par la mise en evidence experimentale de cristaux intracellulaires de caco::(3) dans les racines de colza (brassica napus l. ) cultivees en solution calcique riche en carbonate

Includes bibliography.<br>The engineering behaviour of carbonates differ substantially from quartz based soils. A review of the literature was undertaken in an attempt to identify relevant parameters which could provide the basis for an improved engineering classification. Carbonate content, cementation, crushability, particle size distribution and Atterberg limits were found to be relevant to engineering behaviour of carbonates, and should be included. The maximum obtainable void ratio (emax), which is related to the particle shape distribution, has been proposed as an additional index for carbonate sands. Results from direct shear tests showed that this parameter correlates well with crushability and compressibility. It is recommended that this parameter (emax) as determined in the test devised by Kolbuszewski (1948), should be adopted as an index property for classifying carbonate sands.

Samples of shallow-water carbonates were collected from Jurassic and Cretaceous Italian carbonate platforms and subjected to petrographic, diagenetic and chemostratigraphic analyses (⁸⁷Sr/⁸⁶Sr, δ¹³C_carb, δ¹³C_org, δ¹⁸O). In general, the new chemostratigraphic data generated reflect trends established by previous work, some of which has been carried out on biostratigraphically calibrated reference sections. Consequently, chemostratigraphic correlations (⁸⁷Sr/⁸⁶Sr, δ¹³C_carb) of isotope profiles taken from platform carbonates with well-dated reference sections have allowed the application of high-resolution dating frameworks to the biostratigraphically poorly constrained carbonate platforms. The increased resolution in dating of the Italian carbonate platforms has, furthermore allowed a detailed investigation into the facies response of these carbonate platforms to major geological events. In particular, platform responses to oceanic anoxic events and other periods of major perturbation in the global carbon cycle are analysed (early Toarcian, Aalenian-Bajocian, Oxfordian-Tithonian, Valanginian-Hauterivian, Aptian-Albian, Cenomanian-Turonian, Coniacian-Santonian). Lower Jurassic levels of the Trento Platform record platform devastation in the early Toarcian synchronous with a major negative δ¹³C_carb excursion, followed by platform recovery synchronous with a pronounced δ¹³C_carb positive excursion and return to background values. The Campania-Lucania Platform shows negligible response to the oceanographic events of the early Toarcian even though the characteristic carbon-isotope profile is readily identifiable. The Trento Platform drowned at approximately the Aalenian-Bajocian Stage boundary, synchronously with a reproducible negative followed by positive δ¹³C_carb excursion, whereas the Campania-Lucania Platform underwent a facies transition from oolite to cyclically bedded micrite. The Friuli Platform showed negligible depositional response to the carbon-cycle perturbations of the Kimmeridgian-Tithonian, Valanginian-Hauterivian, Aptian-Albian and Cenomanian- Santonian (as registered in the δ¹³C_carb record). The Campania-Lucania Platform registered flooding and increased levels of organic-matter preservation coincident with pronounced positive δ¹³C_carb excursions at Cenomanian-Turonian and Coniacian-Santonian levels. Observations on the responses of carbonate platforms to oceanographic conditions during periods of global carbon burial lead to the conclusion that temperature excess is a hitherto neglected control on global carbonate accumulation rates.

La compréhension des mécanismes de compaction des roches et des sédiments est importante dans différents domaine des géosciences en particulier pour caractériser la compaction dans les bassins sédimentaires ou le colmatage dans les failles actives. Les objectifs de cette thèse sont d'une part de séparer et de quantifier le rôle respectif de la compaction mécanique et chimique dans les sédiments carbonatés. D'autre part d'obtenir une meilleure compréhension des procédés aboutissant au fluage des roches sédimentaires carbonatées. La perte de porosité par compaction mécanique a été étudiée en réalisant des essais triaxiaux K0 sur des échantillons provenant de plateformes carbonatées. Onze échantillons cimentés par de la calcite faiblement magnésienne et cinq échantillons dolomitisés provenant du Marion Plateau au large de la côte nord-est Australienne (ODP (ocean drilling program) Leg194) ont été compactés de manière uniaxiale à des contraintes effectives allant jusqu'à 70 MPa. La cimentation à faible profondeur à laquelle ces échantillons ont été soumis a créé une structure cimentée stable ayant un fort degré de sur–consolidation et une faible compressibilité. La plupart des échantillons testés étaient tellement cimentés à 30–400 mètres que la perte de porosité à des profondeurs atteignant 4–5 km doit être principalement liée à des procédés chimiques et non à des procédés mécaniques. Pour étudier ces processus chimiques deux autres types d'expériences ont été réalisées. La dissolution sous contrainte est le principal mécanisme responsable du fluage des roches sédimentaires pendant leur enfouissement. Par conséquent la vitesse de déformation de la calcite par dissolution sous contrainte à l'échelle d'un contact a été étudiée. Les résultats obtenus permettent l'identification de l'importance respective de la dissolution sous contrainte résultant de l'application de la contrainte normale et celle de la dissolution au niveau des surfaces 'libres' résultant de l'accumulation de l'énergie élastique ou plastique. Deux mécanismes différents se produisent lors de la dissolution sous contrainte de cristaux de calcite à l'échelle du grain. Dans un premier cas, la diffusion du solide en solution se produit dans le fluide présent à l'interface rugueuse entre la calcite et le poinçon. Dans un deuxième cas, la diffusion se produit le long de fractures qui se propagent du contact vers la partie du cristal soumise à des contraintes plus faibles. Les vitesses de déformation sont plus élevées dans les expériences pour lesquelles la propagation de fractures se produit. De manière générale la vitesse de déformation n'apparait pas comme étant dépendante de la contrainte, mais plutôt de la propagation ou non de fractures. Finalement, les procédés mécaniques et chimiques actifs pendant la compaction ont été étudiés sur des agrégats de cristaux de calcite ou de sables bioclastique. Les expériences montrent que la compaction des sables carbonatés doit être modélisée en prenant en compte à la fois la compaction mécanique et chimique. Dans toutes les expériences la nature du fluide saturant, l'organisation initiale des grains et la taille des grains sont des paramètres important contrôlant la déformation finale ainsi que la vitesse de déformation à une contrainte donnée. La déformation des échantillons saturés avec des fluides non réactifs, e. G. Air ou décane, est moins importante qu'avec des fluides réactifs, puisque dans ce cas la compaction est seulement mécanique. Pendant la phase de chargement, la compaction chimique se produit par dissolution sous contrainte, dont la vitesse est augmentée par la présence de petites fractures au niveau des contacts intergranulaires. Cette interprétation est confirmée par l'observation des échantillons en lame-minces. Les vitesses ultrasoniques se propageant dans les agrégats saturés avec des fluides réactifs ont été mesurées et il a pu être montré que la dissolution et le transport de matière affectant la géométrie des contacts au niveau des grains, ainsi que la fracturation des grains sont probablement les raison de cette diminution de vitesse. En conclusion, la perte de porosité dans les sédiments carbonatés est principalement due à la compaction chimique et très peu à la compaction mécanique. Les procédés chimique de la compaction sont d'une part la dissolution sous contrainte, et d'autre part la dissolution sous contrainte assistée par la propagation sous–critique de fissures. La prédominance de l'un ou l'autre de ces procédés est liée à la nature du fluide présent dans l'espace poreux ainsi qu'à la nature des grains<br>Understanding compaction processes in sediments or rocks is important for instance for the characterisation of compaction in sedimentary basins or for sealing of active fault. The aims of the present study are firstly to separate and quantify the relative role of mechanical and chemical compaction in carbonate sediments. Secondly to better understand chemical compaction processes acting on sediments. The potential for porosity loss by mechanical compaction of platforms carbonate strata was investigated by carrying out K0 triaxial tests. Eleven samples cemented with low, Mg calcite and five dolomitized samples from the Marion plateau, offshore northeast Australia (ODP (ocean drilling program) Leg194) were uniaxially compacted at effective stresses up to 70 MPa. Early cementation of bioclastic carbonate samples created a stable cemented framework with a high degree of over, consolidation and low compressibility. Water saturation of the samples produces weakening of the mechanical strength and greater scatter in the correlation of P, wave velocity versus porosity. Most of the tested samples were already so strongly cemented at 30, 400 meters that further porosity loss during burial up to 4, 5 km depth must occur mainly by chemical rather than mechanical processes. To study chemical processes two other types of experiments were carried out. Pressure solution is the main chemical compaction mechanism affecting sediments during burial, therefore the rate of calcite deformation by pressure solution creep at a single contact was studied. The results enable the identification of the relative importance of pressure solution driven by normal load, and free surface dissolution driven by strain energy. Two different processes occur during pressure solution of calcite crystals at the grain scale. In one case, diffusion of the dissolved solid takes place in the pore fluid present along a rough interface between calcite and the indenter. In the second case, diffusion occurs through cracks that propagate from the contact toward the less stressed part of the crystal. Strain rates are higher for experiments in which crack propagation occurred. Overall it seems strain rates are not really stress dependent but rather dependent on whether crack propagation occurs or not. Eventually, both mechanical and chemical compaction processes were studied on aggregates of calcite and bioclastic carbonate sands. Experimental compaction showed that compaction of carbonates sands should be modelled as a function of both mechanical and chemical compaction also at relatively shallow depth and low temperature. In all cases, the nature of the fluid, the initial grain packing, and the grain size represent important control parameters of the final strain and the strain rates at a given stress. Samples saturated with non, reactive fluids, e. G. Air or decane, show less strain than samples saturated with reactive fluids at the same effective stress since the compaction was only mechanical. During the loading phase, chemical compaction occurs by pressure solution creep which is enhanced by the presence of cracks at the grain, to, grain contacts. This is also supported by the identification of compaction related microstructures in thin, sections. During creep tests, the samples compressibility is controlled by, in order of importance, grain size, stress, and water saturation. Low ultrasonic velocities are especially observed in samples saturated with reactive fluids. Dissolution and transport affecting the grain, to, grain contacts geometry and crack propagation are likely to be the reason for such velocity alteration. In conclusion, porosity loss in carbonate sediments is mostly due to chemical compaction and very little to mechanical compaction. Chemical compaction processes are pressure solution and pressure solution enhanced by subcritical crack growth. The predominance of one or the other mechanism is to be related to the fluid in presence and to the nature of the grains

Submitted by Erika Demachki (erikademachki@gmail.com) on 2016-01-13T15:38:59Z No. of bitstreams: 2 Tese - Edgard Alves Muniz - 2015.pdf: 1352609 bytes, checksum: c9b3cdfa4970aae68eeb4f9b944894ed (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5)<br>Approved for entry into archive by Erika Demachki (erikademachki@gmail.com) on 2016-01-13T15:42:17Z (GMT) No. of bitstreams: 2 Tese - Edgard Alves Muniz - 2015.pdf: 1352609 bytes, checksum: c9b3cdfa4970aae68eeb4f9b944894ed (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5)<br>Made available in DSpace on 2016-01-13T15:42:17Z (GMT). No. of bitstreams: 2 Tese - Edgard Alves Muniz - 2015.pdf: 1352609 bytes, checksum: c9b3cdfa4970aae68eeb4f9b944894ed (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-05-21<br>Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq<br>The latosolic Concretionary Petric Plintosol is the less fertile soil in the bioma Cerrado. Making it to produce food in order to contribute to the Brazilian agribusiness, turns into a great challenge for Science. In addition to this fact, the\pineapple fruits exports are important incomes sources for our Country. For this reason, the present work aimed to assess effects of application, on soil, of calcium carbonate, calcium & magnesium carbonate and calcium sulfate, on productivity of pineapple plant (Ananas comosus L. Merril) var. Pérola cultivated in typical Distrocohesive Yellow Latosol and latosolic Concretionary Petric Plintosol on a same topossequence of Cerrado bioma. Soon after planting, it were applied on both soils, the following equivalent doses\(kg ha-1): on the latossol area – 2000, 2000 and 1000; and on the plintossol area – 3000, 3000 and 1500; of calcium carbonate, calcium & magnesium carbonate and calcium sulfate, respectively. As effects, the fruits production averages (t ha-1), in both soils were: 8,32; 12,94; 13,82; 15,09; 5,02; 12,60; 14,11; e 14,82, respectively, in the same sequence above. The essays were set up in 2010, in a region of Anápolis, Goiás State, latitude 16º19ˈ 36 ̎ S, longitude 48º57ˈ 10 ̎ W and altitude 1017 m. The yearly pluviosity average is 1.200 mm, and the temperature oscillates between 21 and 35ºC; the climate is classified as Aw according to Köppen system. The harvest was achieved in 2012. The experimental design was in randomized blocks. Each plot measured 1,20 x 6,60 m and were four the number of treatments with five replications. The three products, in the mentioned equivalent doses, induced the latosolic Concretionary Petric Plintosol studied to reach a pineapple Pérola production capacity equivalent to the typical Distrocohesive Yellow Latosol. Calcium sulfate, calcium carbonate and calcium & magnesium carbonate, individually, increased the tenor of changeable bases in the upper layers of both soils, wich made it possible to obtain greater pineapple Pérola yielding.<br>Plintossolo Pétrico Concrecionário latossólico é o menos fértil dos solos cerradinos. Fazê-lo produzir alimentos para contribuir com o agronegócio brasileiro, tornase um desafio para a ciência. Em adição a este fato, abacaxi é uma importante fonte de divisas para o país. Por estas razões, o presente trabalho objetivou avaliar efeitos de aplicações, no solo, de calcário calcítico, calcário dolomítico e gesso agrícola sobre a produtividade do abacaxizeiro (Ananas comosus L. Merril) var. Pérola cultivado em Latossolo Amarelo Distrocoeso típico e em Plintossolo Pétrico Concrecionário latossólico de uma mesma topossequência de bioma Cerrado. Logo após o plantio, foram aplicadas, aos dois solos, as seguintes doses equivalentes (kg ha-1): na área de latossolo – 2.000, 2.000 e 1.000; e na área de plintossolo – 3000, 3000 e 1 .500 de calcário calcítico, calcário dolomítico e gesso agrícola, respectivamente. Como efeitos, as produções médias de frutos (t ha-1), nos dois solos, foram: 8,32; 12,94; 13,82; 15,09; 5,02; 12,60; 14,11; e 14,82, na mesma ordem das doses equivalentes descritas acima. Os ensaios foram instalados em 2010, no município de Anápolis (GO), com latitude de 16º19ˈ 36 ̎ S, longitude 48º57ˈ 10 ̎ W e altitude 1017 m. A média anual de pluviosidade é de 1.200 mm e a temperatura oscila entre 21 e 35ºC; clima é classificado como Aw no sistema Köppen. A colheita realizou-se em 2012. O delineamento experimental foi em blocos ao acaso. Cada parcela mediu 1,20 x 6,60 m, e foram quatro os tratamentos de cinco repetições. Os três insumos, nas doses equivalentes mencionadas, induziram o Plintossolo Pétrico Concrecionário latossólico estudado a atingir uma capacidade de produção de abacaxi Pérola estatisticamente igual à do Latossolo Amarelo Distrocoeso típico. O gesso agrícola, o calcário dolomítico e calcário calcítico, individualmente, aumentaram os teores de bases trocáveis nas camadas mais superficiais dos dois solos, o que possibilitou a obtenção de maiores produtividades do abacaxizeiro Pérola.

En raison de leur porosité élevée, les roches carbonatées forment d'importants réservoirs d'eau et d'hydrocarbures, et conviennent également à d'autres applications telles que le stockage de CO2 ou des déchets nucléaires. Cependant, le compactage localisé dans les roches carbonatées affecte le champ des contraintes et les propriétés hydromécaniques de ces roches, entraînant des déformations inélastiques et des dommages avec des impacts économiques, environnementaux et sociaux potentiels. Des études antérieures sur le terrain et des études expérimentales en laboratoire que dans les roches carbonatées poreuses, contrairement aux grès, une variété de micromécanismes tels que l'effondrement des pores, le broyage des grains, la petre de cimentation, la plasticité des cristaux et la dissolution sous contrainte peuvent entraîner une densification inélastique. En raison de la coexistence de ces multiples processus inélastiques et de leur interactions, le micromécanisme prédominant à l'origine du processus de localisation et de rupture reste mal compris.Cette thèse de doctorat présente une étude expérimentale sur les mécanismes de déformation régissant le comportement mécanique et le mode de rupture des roches carbonatées à haute porosité. A cet effet, le Tuffeau de Maastricht, un calcaire sédimentaire bioclastique présentant jusqu'à 52% de porosité, a été testé à l'état sec. Cette étude s'est concentrée sur la façon dont le chemin des contraintes, la pression de confinement et l'orientation de la stratification influent sur l'apparition et la propagation des bandes de compaction. Trois campagnes expérimentales principales sont menées sur des éprouvettes cylindriques pour étudier la transition fragile-ductile :compression isotrope,compression uniaxiale et compression triaxiale. Une analyse systématique du comportement anisotrope du Tuffeau de Maastricht est effectuée sur des échantillons qui ont été forés perpendiculairement, obliquement 45° et parallèlement au plan de la stratification. La micro-tomographie à rayons X à haute résolution est utilisée pour obtenir des images 3D de l'ensemble de l'échantillon en cours de chargement. Les images acquises sont traitées et des mesures de plein champ ont été utilisées pour élucider les mécanismes d'initiation et de propagation des zones de compactage localisées. Les variations de porosité pendant le chargement sont mesurées macroscopiquement et localement. L'utilisation systématique des rayons X combinée à l'utilisation de l'analyse d'image avancée et de la corrélation d'images numérique fournit une information 3D quantitative du champ de déformation et de son évolution pendant un test.Deux modes de rupture sont identifiés, selon les mesures de porosité et la CIVD: les bandes de cisaillement contractantes développées à basse pression de confinement et les bandes de compaction formées perpendiculairement à la contrainte principale majeure de compression à un confinement plus élevé. Ces bandes se développent à contrante déviatoire presque constante et se propagent dans tout l'échantillon, phase marquée par des chutes épisodiques de la contrainte deviatoire. Les essais de compression triaxiale conduit à des niveux de déformation axiale plus élevée présentent trois phases distinctes: une phase initiale quasi-linéaire, suivie par un plateau de contrainte déviatoire, enfin un durcissement post-plateau. L'observation essentielle de ces expériences est l'existence d'un mécanisme de dégradation del la cimentation entre grains qui transforme l'échantilon cohésif et frottant en un miliu granulaire purement frottant. D'autres expériences réalisées sur du sable obtenu par dégradation artificielle de la roche originelle mettent l'accent sur cette phase de déstructuration qui se produit lors du plateau de la contrainte déviatoire. Les résultats expérimentaux mettent également en évidence la forte influence due à l'anisotropie sur le comportement mécanique du matériau étudié<br>Given their high porosity, carbonates form important water and hydrocarbons reservoirs, and they are also suitable for other applications such as CO2 storage and nuclear waste disposal. However, localized compaction in carbonates affects the stress field and the hydromechanical properties of these rocks leading to inelastic deformation and failure with potential economic, environmental and social impacts. Previous field and experimental studies have shown that in porous carbonates, unlike sandstones, a variety of micromechanisms such as pore collapse, grain crushing, debonding, crystal plasticity and pressure solution can potentially lead to inelastic compaction. Due to the coexistence of such multiple inelastic processes and the interplay among them, the dominant micromechanism responsible for failure remains poorly understood.This doctoral thesis presents an experimental investigation into the deformation mechanisms governing the mechanical behavior and failure mode of high porosity carbonate rocks. To this end, Tuffeau de Maastricht, a bioclastic sedimentary limestone exhibiting up to 52% porosity, has been tested under dry conditions. This study focuses on how stress path, confining pressure and bedding orientation affect the onset and propagation of localized compaction. Three main experimental campaigns are conducted on cylindrical specimens of 11.5 mm diameter and 22 mm height to study the brittle-ductile transition: (i) isotropic compression, (ii) uniaxial compression, and (iii) triaxial compression tests at confining pressures ranging from 1 to 5 MPa. A systematic analysis of the anisotropic behavior of Tuffeau de Maastricht is conducted on samples cored perpendicular, oblique 45° and parallel to the bedding plane. High resolution x-ray computed tomography (CT) is used to obtain 3D images of the entire specimen under loading. The acquired images are processed and full-field measurements have been used to elucidate the mechanics of initiation and propagation of localized compaction. Porosity variations during loading are measured macroscopically as well as locally. The porosity measurements are performed over a REV, which is defined with the use of statistical tools. The systematic use of x-ray micro tomography combined with the use of advanced image analysis and Digital Image Correlation (DIC) provides a quantitative 3D information the strain field inside a sample and its evolution during a test.Two failure modes are identified, based on porosity measurements and DIC: compactive shear bands at low confining pressure, and compaction bands (perpendicular to the maximum compressive stress) at higher confinement. These bands develop at essentially constant deviator stress and propagate through the whole sample punctuated by episodic stress drops. Triaxial compression tests at much higher axial strain present three distinct phases: (1) an initial quasi-linear increase of deviator stress, followed by (2) a plateau and (3) a post-plateau hardening. The essential observation from these experiments if the occurrence of a debonding phase which converts the specimen from rock-like to sand-like. A second localization, typical of dense sand, eventually occurs for very axial strain. Additional experiments that are performed on artificially debonded specimens emphasize this destructuration phase during the plateau of deviator stress. The experimental results also highlight the strong anisotropy of the mechanical behavior of the studied material

This thesis describes a series of experiments both in solution systems and soil systems to study the precipitation of calcium carbonate in soils and the effects of the precipitation on soil pH after urea had been applied. (1) A gas bubbling system has been established which introduces ammonia at a steady rate to the reaction solution and keeps it equilibrated at 0.00484 atm partial pressure of carbon dioxide. (2) In a non-seeded system, the effects of calcium, urea, Mg (magnesium), P (phosphate), and DOC (water-dissolved organic matter) on the precipitation were examined individually and in various combinations. Calcite and vaterite were found in the 10 mM CaC1₂ solutions with and without the addition of urea. When the solutions contained Mg, P, and DOC, vaterite was not found. Aragonite was found in the reaction solution containing 5 mM Mg. In high initial concentration of P (5x10^-4 M) , the formation of calcium phosphate (amorphous by X-ray analysis) catalysed the formation of calcite. The effects of urea and Mg on the precipitation are negligible compared with the effects of P and DOC. (3) In a seeded system, 16 sets of experiments with four sizes of calcite-seeds were carried out to study the precipitation rate of calcium carbonate. This was described by the equation LR=-4.113±0.132 + 0.379±0.029 LWA + LSI where LR=log (precipitation rate, PR, in mole litre^-1 min^-1), LWA= log (newly formed calcium carbonate, g ml^-1), and LSI=log (degree of supersaturation of calcium carbonate, SI). (4) A wide range of concentrations of urea (0.05, 0.1, 0.3, 0.5, 0.7, and 1 M) were added to three soils (Beg., Uni., and VWH) with or without the addition of 5 per cent of calcite (10-15 μm) to establish a rate model for the precipitation of calcium carbonate in soils. The precipitation model (in logarithmic form) in soils is lnPR=-9.47±0.30 + lnK_SOIL + 0.379±0.029 InWA + InSI - 1686±703 P - 6.13±3.02 DOC + 3854±1775 (P DOC) where P and DOC are the concentrations in soil solutions, and lnK_SOIL is the effect of soils on the precipitation, which is - 1.98, 0.43, and -0.10 for Beg., Uni., and VWH soils respectively. The amount of newly formed calcium carbonate is about a third to a half of the amount of ammoniacal-N released by urea hydrolysis. It was able to reduce the increase of soil pH by more than 0.6 pH units in some circumstances.

Dans le cadre du suivi environnemental de ses installations en conditions nominales d’exploitation ou en situation accidentelle, le CEA doit assurer la mise en place de méthodes et d’outils opérationnels permettant de mesurer, contrôler et prédire les rejets de ses installations dans l’atmosphère, les sols et les nappes. Cette thèse s’inscrit ainsi dans la mise en place d’un outil de transport réactif permettant de prédire la migration de radionucléides en concentration trace tels que 90Sr et 137Cs, les principaux radionucléides d’intérêt, dans les sols et les roches. L’objectif de cette thèse est d’évaluer l’applicabilité et le caractère prédictif d’un modèle couplé chimie-transport, dans le cas de la migration de Cs et Sr dans un sédiment naturel représentatif de la couche aquifère sous-jacente au site de Cadarache. Le modèle de rétention utilisé est basé sur la Théorie des Echangeurs d’Ions multi-sites (TEI), intégré dans PhreeqC couplé à HYDRUS 1D (HP1) ou dans Crunchflow.La caractérisation des propriétés physico-chimiques du sédiment étudié et l’identification des minéraux réactifs a permis dans un premier temps d’élaborer une base de données de rétention de Sr2+, Cs+ et Ca2+ (principal cation du milieu) sur les minéraux argileux majoritairement présents, illite et smectite. La construction de cette base de données s’est faite à partir d’une révision critique des données de la littérature, complétée par l’acquisition de données manquantes. A partir de cette base de données, et faisant l’hypothèse de l’additivité des propriétés de rétention des minéraux purs dans un matériau considéré comme un mélange de minéraux purs, il a été possible, dans un second temps, de vérifier l’applicabilité du modèle de rétention au cas de l’adsorption de Sr2+ et Cs+ sur le sédiment.Enfin, ce modèle de rétention a pu être couplé à un modèle de transport, et appliqué au cas de la migration de Sr et Cs dans des colonnes de sédiment. Ces expériences ont été réalisées sur deux types de colonne, à l’échelle centimétrique sur des colonnes standards et à l’échelle décimétrique sur un banc expérimental équipé d’un générateur X permettant de suivre en continu les paramètres physico-chimiques au sein de la colonne. Les simulations des expériences de transport réactif de Sr par le modèle d’échange d’ions multi-sites, couplé à l’équation d’advection-dispersion ont pu reproduire convenablement les courbes de percée de Sr sans aucun ajustement des paramètres. Les coefficients de dispersivité de chaque colonne ont été déterminés lors d’expériences de transport non réactif à l’aide de traceurs inertes (2H, Cl- et I-). Par ailleurs, les courbes de percée de Cs semblent plus difficiles à reproduire, ce qui serait imputable aux incertitudes existant encore sur les paramètres de rétention relatifs à cet élément ou un effet cinétique.La bonne concordance entre les résultats des expériences de transport réactif de Sr en colonne à deux échelles différentes et les simulations ont montré que le modèle de transport réactif mis en place permet de reproduire le comportement de Sr dans le sédiment de Cadarache étudié, sans ajustement de paramètres, en considérant la rétention chimique par un processus d’échange d’ions sur les minéraux argileux du système. Cette première étape indispensable à l’évaluation du modèle mis en place permet de confirmer le caractère prédictif de ce modèle, dans la mesure où les conditions physico-chimiques sont bien contraintes<br>As part of the environmental monitoring of its installations under nominal operating conditions or in accident situation, CEA must ensure the implementation of operational methods and tools to measure, control and predict the discharge of its installations into the environment, atmosphere, soil and groundwater. This work is part of the implementation of a reactive transport tool, which allows predicting the migration of radionuclides in trace concentration such as 90Sr and 137Cs, the main radionuclides of interest, in soils and rocks. The aim of this thesis is to evaluate the applicability and predictive nature of a coupled chemistry-transport model in the case of migration of Cs and Sr in a natural sediment, representative of the aquifer underlying the nuclear site of Cadarache. The retention model used is based on the Multi-Site Ion Exchange Theory, integrated in PhreeqC coupled with HYDRUS 1D (HP1) or Crunchflow.The characterization of the physico-chemical properties of the sediment studied and the identification of the reactive minerals allow to develop a database of retention of Sr2+, Cs+ and Ca2+ (major cation of the medium) on the clay minerals mostly present, illite and smectite. The construction of this database was based on a critical review of the data in the literature, supplemented by the acquisition of missing data. From this database and assuming the additivity of the retention properties of pure minerals in a material considered as a mixture of pure minerals, it was possible to verify the applicability of the retention model in the case of the adsorption of Sr2+ and Cs+ on the sediment.Finally, this retention model could be coupled to a transport model and applied to the case of the migration of Sr and Cs in sediment columns. These experiments were carried out on two types of column, at the centimeter scale on standard columns and at a decimetric scale on an experimental device equipped with a X generator recording continuously the physicochemical parameters within the column. Simulations of the Sr reactive transport experiments by the multi-sites ion exchange model coupled with the advection-dispersion equation were able to adequately reproduce the Sr breakthrough curves without any parameter adjustments. The dispersivity coefficients of each column were determined in non-reactive transport experiments using inert tracers (2H, Cl- and I-). Moreover, the Cs breakthrough curves seem more difficult to reproduce, which could be due to the uncertainties still existing on the retention parameters related to this element or a kinetic effect.The good agreement between the results of the reactive Sr transport experiments in a column at two different scales and the simulations showed that the reactive transport model implemented allows reproducing the behavior of Sr in the Cadarache sediment without parameter adjustment by considering the chemical retention by an ion exchange process on the clay minerals of the system. This first step, essential to the evaluation of the model confirms the predictive nature of this model, insofar as physicochemical conditions are well constrained

Dans le cadre de problématiques liées à l’industrie nucléaire (stockage géologique profond, démantèlement et suivi environnemental de site), le but de cette étude a été de caractériser les interactions uranium-colloïdes grâce à une approche de fractionnement en ligne couplée à une multi-détection. Le principal avantage ici est de fournir un maximum d’informations sur la répartition de l’uranium au sein des différentes populations colloïdales. En faisant varier les paramètres-clés du protocole de lixiviation employé, différents scénarii potentiellement impliqués dans la mobilisation colloïdale de l’uranium ont été étudiés. Chacun des échantillons obtenus a ensuite été caractérisé et ainsi, la taille (masse molaire, rayon de giration et rayon hydrodynamique) et la nature ainsi que la quantité d’uranium transporté par les colloïdes mis en évidence ont été déterminées. Les mécanismes d’interaction uranium-colloïdes mis en jeu ont également été étudiés<br>In order to assess the fate of actinides in the environment, it is essential to identify the interactions between actinides and soil components. In the case of problems connected to the nuclear industry (deep geologic storage, dismantling and environmental monitoring of nuclear sites), the purpose of this study was to characterize the uranium-colloids interactions by on-line fractionation multi-detection methods. The main advantage here is to supply a lot of information on the uranium distribution within the various colloidal populations. By varying the keys-parameters of a batch leaching protocol, different scenarios potentially implied in the colloidal mobilization of uranium were studied. Each sample collected was also characterized and their size (hydrodynamic and gyration radius), their nature as well as the uranium concentration carried by colloids were determined. The mechanisms of the uranium-colloids interactions were also studied

La restauration des sols forestiers acides et leur dynamique sont abordées par l'étude des effets des formes et quantités d'amendements apportés, en interaction avec la qualité de l'humus. Le caco#3, caco#3+mgo et caso#4 sont apportés en surface avec des doses de 0, 0. 56, 2. 8 et 5. 6 t/ha équivalent cao et les principaux résultats sont: le sol: la valeur du ph du sol est augmentée de 4 unités ph dans les couches de surface (a#1) et d'une unité ph en moyenne en profondeur (b) avec les amendements carbonates. La restauration a été rapide (moins de 7 mois) dans les premiers centimètres du sol avec une migration également de particules de carbonates (>40% du ca) de la litière vers la couche a#1#1 (-3 cm). La saturation n'est pas modifiée dans les couches inferieures du (b) (16 a 21 cm), sauf pour la forme sulfate où elle a augmente de 50% par rapport au témoin. Les mécanismes d'échanges de l'aluminium par le calcium expliquent ces changements sur les surfaces d'échange; la solution du sol: par rapport au témoin, la composition des eaux a été modifiée rapidement (2 mois) par le sulfate avec un enrichissement du flux d'aluminium et de calcium. L'effet des carbonates sur la solution, sous (b) (-21 cm), a été moins rapide (7 mois). Les analyses des eaux montrent une modification de la dynamique de l'azote. Dans le traitement carbonate le mécanisme reste le même et l'anion dominant est le nitrate. Dans le traitement caso#4, l'anion vecteur est le sulfate, 52% de l'azote d'azote est transporté hors du profil sous forme d'ammonium

L'objectif de la thèse est de traiter des sédiments marins et des sols fins équivalents (fines de carrière) considérés comme des déchets, par un procédé de solidification/stabilisation et de les valoriser en matériau pour des sous couches routières. Ces traitements ont donné lieu à des mélanges composites sédiments-liants et/ou ajouts de cendres volantes, de fumée de silice, de produits chimiques réactifs et de fibres suivis d'une analyse comportementale des performances mécaniques et de durabilité. Après avoir sélectionné un panel représentatif de sédiments marins et une fine de carrière, une phase de caractérisation a été entreprise sur les paramètres déterminants en vue de traiter ces sédiments. Elle repose sur l'étude des propriétés physiques (répartition des grains, limites d'Atterberg) et chimiques (la teneur en matière organique et en carbonates). Les différentes caractéristiques, dosages et paramètres dimensionnels des constituants (ciment, chaux, cendre volante, fumée de silice, sables correcteur, produit chimique réactif et fibres naturelle et géosynthétiques) des mélanges sont déterminés. Le programme expérimental complet est présenté, il intéresse les sédiments marins à stabiliser ou solidifier. Les essais mécaniques de résistance et de durabilité (compression simple, traction indirecte, mouillage-séchage) ont été effectués sur échantillons cylindriques. L'analyse et l'interprétation des résultats ont permis de mieux cerner les différents facteurs influant sur la résistance à la compression et à la traction indirecte des mélanges traités avec des additions de liants hydrauliques et de liant pouzzolanique, puis avec des ajouts spécifiques de fumée de silice, de sable correcteur et de produits chimiques réactifs. Une phase innovante a porté sur l'utilisation de fibres déchets dans les mélanges. Ces fibres naturelle (lin) et artificielles (géosynthétiques) ont été proposées pour améliorer le comportement mécanique des mélanges de sédiments marins et/ou fine de carrière. En conclusion, pour les dosages économiques retenus et les mélanges étudiés, une application en sous couche routière est possible (classes S1à S5). La teneur en matière organique des sédiments marins a une forte influence sur l'efficacité des traitements des sédiments marins aux liants. Les renforts fibreux sont tout à fait prometteurs et l'idée de covaloriser deux déchets constitue une avancée dans la gestion durable et la valorisation des sédiments.

Sur le site minier orphelin de Sentein (Pyrénées), la dynamique de Zn, Pb et Cd est étudiée à l'échelle du bassin versant amont du Lez, en couplant des approches géochimiques et minéralogiques. A partir de la minéralisation, primaire et naturelle, l'exploitation minière a redistribué les métaux en plusieurs sources secondaires (sols contaminés, résidus d'extraction et de traitement). Les résidus de traitement constituent le principal réservoir de métaux. Dans ce contexte carbonaté, l'exportation des métaux sous forme dissoute est limitée par la formation de phases minérales secondaires. L'érosion mécanique est le mécanisme majeur de mobilisation des métaux. A l'exutoire du bassin, la dispersion particulaire des métaux est dominante, notamment lors des crues. La contribution de ce site minier au flux de métaux transportés par la Garonne est estimée<br>On the orphan Sentein mining district (Pyrénées), the Zn, Cd and Pb dynamics is studied at the scale of the Lez upstream catchment, with geochemical and mineralogical approaches. From the primary and natural mineralization, mining exploitation has lead to the redistribution of metal into several secondary sources (contaminated soils, extraction wastes and tailings). Tailings are the main storage compartment of metals. Submitted to erosion, they constitute the principal source. In this carbonated context, the metal exportation under dissolved form is limited by the formation of secondary minerals. Runoff and erosion are dominant processes for metal mobilization. At the catchment outlet, particulate dispersion is dominant specially, during storm events. The contribution of this mining site to Garonne metal fluxes is assessed

S’han investigat les poblacions naturals d’Arabidopsis thaliana de Catalunya per identificar mecanismes d’adaptació local als sòls carbonatats. Després de caracteritzar les propietats químiques dels sòls natius, petits rodals de poblacions biològiques d' A. thaliana (que anomenem “demes”), es van realitzar experiments anuals de camp, en parcel·les amb diferents nivells de carbonats al sòl, per avaluar l’aptitud diferencial entre els “demes”. La progènie d’aquests demes va mostrar una millor aptitud en el sòl control, sense carbonats. Les diferencies en l’aptitud dels demes per créixer l sòl carbonatat està associada amb el percentatge de CaCO3 dels sòls natius. Aquest fet confirma que el nivell de carbonats al sòl és el factor limitant per a l’adaptació local. Els demes contrastants A1 (moderadament tolerant) i T6 (sensible) es varen seleccionar per analitzar les característiques fisiològiques. Quan creixen bé en presencia de carbonats o bé amb deficiència de ferro s’observen diferencies en el contingut de clorofil·les, l’activitat de SOD i el perfil de compostos fenòlics exsudats per les arrels. El deme tolerant A1 presenta l’al·lel AtFPN2 com el genotip de referència Col.0. Per contra s’ha trobat que el deme sensible T6, presenta la seqüència de l’al·lel com Ts-1. La presencia de l’al·lel dèbil de AtFPN2 de Ts-1 podria justificar l’elevada acumulació de metalls divalents a la fulla del deme sensible T6. Creuaments realitzats entre demes tolerants i sensibles revelen l’herència d’aquests trets. En la F3 es van seleccionar famílies tolerants i sensibles per fer l’anàlisi de “bulk-segregation”, que encara esta en procés de realització. Per tal d’identificar gens candidats per a l’adaptació als sòls carbonatats, s’ha utilitzat una col·lecció HAP-MAP provinent de NASK. Aquestes accessions van ser plantades en sol carbonatat i sòl control i es va dur a terme un seguiment del creixement i un anàlisis ionòmic de la part aèria. El Genome wide association analysis (GWAS) ens ha proporcionat una llista de gens potencialment relacionats amb la tolerància als sòls carbonatats. En conclusió, els nostres resultats demostren que les plantes d’A. thaliana que tenen com a habitat natural sòl amb concentracions moderades o baixes de carbonat són més tolerants als carbonats que les plantes que viuen en sòls sense carbonats. Aquesta “tolerància” és heretable i el GWAS ha revelat múltiples gens candidats a ser els responsables d’aquesta tolerància al sòl carbonat. Els resultats que s’obtindran amb el BSA-seq anàlisis proporcionaran informació útil i addicional per a la identificació dels gens clau involucrats en aquesta tolerància.<br>Natural populations of Arabidopsis thaliana from Catalonia were investigated to identify mechanisms of local adaptation to carbonate soils. After characterizing the chemical properties of the native soils of multiple small stands of A. thaliana (called “demes”), multi-year common garden experiments, based on contrasting soil carbonate levels, were performed to identify differential fitness among demes. Progenies from these demes performed better on control soil without carbonate. However, fitness differences among demes on carbonate soils were associated with the percentage of CaCO3 in the native soils. This confirms that the soil carbonate level is a driving factor for local adaptation. Contrasting demes A1 (moderately tolerant) and T6 (sensitive) were selected for analyzing physiological traits. When growing either with carbonate or under iron deficiency both demes differed in chlorophyll content, SOD activity, and the profile of phenolic compounds in root exudates. Tolerant deme A1 has the AtFPN2 allele like the reference genotype Col.0. Contrastingly, in sensitive deme T6 the allele sequence is as in Ts-1. The presence of the weak allele of AtFPN2 of Ts-1 could justify the higher accumulation of divalent metals in the leaf of deme T6. Crosses between tolerant and sensitive demes revealed heritability of these traits. In F3, tolerant and sensitive families were selected for bulk segregation analysis, which is still under progress. For further identifying candidate genes for adaptation to carbonate soil, a Hap-Map collection from NASK was used. Different accessions were grown in carbonate and control soils. Growth and shoot ionome was compared to plants growing on non-carbonate soil. Genome wide association analysis (GWAS) provided a list of genes potentially related with plant tolerance to carbonate soils. In conclusion, our results demonstrate that A. thaliana plants naturally adapted to soil with moderate-low carbonate concentrations are more carbonate tolerant than plants from soils without carbonate. This tolerance is inheritable and GWAS revealed multiple candidate genes responsible for tolerance to carbonate soil. BSA-seq results will provide further useful information for the identification of the key genes involved.

Le transfert des solutés en milieu crayeux est étudié tout d'abord sur le site expérimental de Béthune (Pas-de-Calais) dans la nappe semi captive de la craie sénonienne. Différents traceurs sont injectés dans les puits de pompage et montrent des courbes divergentes par rapport aux courbes théoriques, phénomène du sans doute à l'oxydoréduction, l'acidification du milieu, l'interaction être traceurs et phase solide. D'autre part les expériences sur colonnes montrent les mêmes divergences qui prouvent que les échanges entre les deux milieux se font essentiellement par diffusion moléculaire, le coefficient de l'uranine dans la craie étant estimé à 3,4. 10-10 m²/s-1.

COSTA, P. A. Pedogênese de um solo calcário e alterações de seus atributos em resposta a irrigação. 2012. 115 f. Dissertação (Mestrado em Agronomia/Solos e Nutrição de Plantas) - Centro de Ciências Agrárias, Universidade Federal do Ceará, Fortaleza, 2012.<br>Submitted by Francisco Lacerda (lacerda@ufc.br) on 2014-09-17T20:18:05Z No. of bitstreams: 1 2012_dis_pacosta.pdf: 3758109 bytes, checksum: 488951ad9986c9b054dc386e926b2a48 (MD5)<br>Approved for entry into archive by José Jairo Viana de Sousa(jairo@ufc.br) on 2014-09-24T17:21:26Z (GMT) No. of bitstreams: 1 2012_dis_pacosta.pdf: 3758109 bytes, checksum: 488951ad9986c9b054dc386e926b2a48 (MD5)<br>Made available in DSpace on 2014-09-24T17:21:26Z (GMT). No. of bitstreams: 1 2012_dis_pacosta.pdf: 3758109 bytes, checksum: 488951ad9986c9b054dc386e926b2a48 (MD5) Previous issue date: 2012<br>Water is a priceless natural resource. More than an essential input to production is a strategic resource for economic development. The semiarid region, as well as the rest of the world, suffer more with climate change associated with global warming. These climate changes have impacts on both supply and demand for water in this region. In northeastern Brazil, where there is an uneven distribution of rainfall, agricultural production is substantially improved through the use of irrigation. The adoption of the use of irrigation in these semiarid regions leads to changes in soil moisture regime and may even change its properties and processes. The objective of this study was to investigate the effects during 23 years of irrigation on calcareous soils in semiarid Ceará, with emphasis on the study of pedogenetic changes provided by this practice. The areas chosen for study are located in Chapada do Apodi located in the city of Limoeiro do Norte - Ce. 8 amostrgens were performed in each area (in the irrigated area and the area outside and adjacent to the pivot). Subsequently, in each of the areas, trenches were opened to perform the morphological descriptions and collected soil samples for physical characterization, chemical, mineralogical and micromorphological. The results indicate significant differences have occurred in the irrigated area compared to non-irrigated area, and verified the increased dissolution of CaCO3 and increased levels of calcium, sodium and phosphorus. Furthermore, the flooded soil has changed its physical characteristics, and found an increase in density of particles decreased permeability of the soil air and the formation of pores less continuous. The analysis results showed that the profiles of 23 years of irrigation had effect on irrigated soil, making it more evolved in comparison to non-irrigated, it was verified by the results obtained in morphology with increasing soil thickness in physics with a lower silt / clay ratio and higher clay content in soil, mineralogy with evidence of increased neoformation of kaolinite and interstratified minerals, in micromorphology with the highest degree of pedalidade. The irrigated soil was classified as Chernosol by presenting chernozênico horizon followed by an incipient B horizon and possess high activity clay.<br>A água é um recurso natural de valor inestimável. Mais que um insumo indispensável à produção é um recurso estratégico para o desenvolvimento econômico. A região semiárida, assim como o resto mundo, sofre cada vez mais com as alterações climáticas, associadas ao aquecimento global. Essas mudanças climáticas têm impactos tanto na oferta como na demanda por água nessa região. Na região Nordeste do Brasil, onde há uma distribuição irregular de chuvas, a produção agrícola é substancialmente melhorada através do uso da irrigação. A adoção do uso da irrigação nessas regiões semiáridas causa modificações no regime de umidade dos solos e pode ainda alterar suas propriedades e processos. O objetivo deste trabalho foi investigar os efeitos causados durante 23 anos de irrigação sobre solos calcários no semiárido cearense, com ênfase no estudo das alterações pedogenéticas proporcionadas pelo uso dessa prática. As áreas escolhidas para o estudo estão localizadas no perímetro irrigado localizado na Chapada do Apodi no município de Limoeiro do Norte-CE. Foram realizadas 8 tradagens em cada área (na área irrigada e na área externa e limítrofe ao pivô). Posteriormente, em cada uma das áreas, foram abertas trincheiras para realização das descrições morfológicas e coleta de amostras de solo para fins de caracterização física, química, mineralógica e micromorfológica. Os resultados referentes às tradagens indicam terem ocorrido diferenças significativas na área irrigada quando comparada à área não irrigada, sendo verificadas a intensificação da dissolução de CaCO3 e o aumento dos teores de cálcio, sódio e fósforo. Além disso, o solo irrigado sofreu alterações dos seus atributos físicos, sendo verificado aumento da sua densidade de partículas, diminuição da permeabilidade do solo ao ar e a formação de poros menos contínuos. Os resultados das análises dos perfis mostraram que os 23 anos de irrigação tiveram efeito no solo irrigado, tornando-o mais evoluído em comparação ao não irrigado, isso foi verificado através dos resultados obtidos na morfologia com aumento da espessura do solum, na física com a menor relação silte/argila e maior conteúdo argila nesse solo, na mineralogia com indícios de aumento da caulinita e neoformação de minerais interestratificados e na micromorfologia com o maior grau de pedalidade. O solo irrigado foi classificado como Chernossolo Háplico carbonático saprolítico, por apresentar horizonte A chernozênico seguido de horizonte B incipiente e possuir argila de atividade alta.

A Ãgua à um recurso natural de valor inestimÃvel. Mais que um insumo indispensÃvel à produÃÃo à um recurso estratÃgico para o desenvolvimento econÃmico. A regiÃo semiÃrida, assim como o resto mundo, sofre cada vez mais com as alteraÃÃes climÃticas, associadas ao aquecimento global. Essas mudanÃas climÃticas tÃm impactos tanto na oferta como na demanda por Ãgua nessa regiÃo. Na regiÃo Nordeste do Brasil, onde hà uma distribuiÃÃo irregular de chuvas, a produÃÃo agrÃcola à substancialmente melhorada atravÃs do uso da irrigaÃÃo. A adoÃÃo do uso da irrigaÃÃo nessas regiÃes semiÃridas causa modificaÃÃes no regime de umidade dos solos e pode ainda alterar suas propriedades e processos. O objetivo deste trabalho foi investigar os efeitos causados durante 23 anos de irrigaÃÃo sobre solos calcÃrios no semiÃrido cearense, com Ãnfase no estudo das alteraÃÃes pedogenÃticas proporcionadas pelo uso dessa prÃtica. As Ãreas escolhidas para o estudo estÃo localizadas no perÃmetro irrigado localizado na Chapada do Apodi no municÃpio de Limoeiro do Norte-CE. Foram realizadas 8 tradagens em cada Ãrea (na Ãrea irrigada e na Ãrea externa e limÃtrofe ao pivÃ). Posteriormente, em cada uma das Ãreas, foram abertas trincheiras para realizaÃÃo das descriÃÃes morfolÃgicas e coleta de amostras de solo para fins de caracterizaÃÃo fÃsica, quÃmica, mineralÃgica e micromorfolÃgica. Os resultados referentes Ãs tradagens indicam terem ocorrido diferenÃas significativas na Ãrea irrigada quando comparada à Ãrea nÃo irrigada, sendo verificadas a intensificaÃÃo da dissoluÃÃo de CaCO3 e o aumento dos teores de cÃlcio, sÃdio e fÃsforo. AlÃm disso, o solo irrigado sofreu alteraÃÃes dos seus atributos fÃsicos, sendo verificado aumento da sua densidade de partÃculas, diminuiÃÃo da permeabilidade do solo ao ar e a formaÃÃo de poros menos contÃnuos. Os resultados das anÃlises dos perfis mostraram que os 23 anos de irrigaÃÃo tiveram efeito no solo irrigado, tornando-o mais evoluÃdo em comparaÃÃo ao nÃo irrigado, isso foi verificado atravÃs dos resultados obtidos na morfologia com aumento da espessura do solum, na fÃsica com a menor relaÃÃo silte/argila e maior conteÃdo argila nesse solo, na mineralogia com indÃcios de aumento da caulinita e neoformaÃÃo de minerais interestratificados e na micromorfologia com o maior grau de pedalidade. O solo irrigado foi classificado como Chernossolo HÃplico carbonÃtico saprolÃtico, por apresentar horizonte A chernozÃnico seguido de horizonte B incipiente e possuir argila de atividade alta.<br>Water is a priceless natural resource. More than an essential input to production is a strategic resource for economic development. The semiarid region, as well as the rest of the world, suffer more with climate change associated with global warming. These climate changes have impacts on both supply and demand for water in this region. In northeastern Brazil, where there is an uneven distribution of rainfall, agricultural production is substantially improved through the use of irrigation. The adoption of the use of irrigation in these semiarid regions leads to changes in soil moisture regime and may even change its properties and processes. The objective of this study was to investigate the effects during 23 years of irrigation on calcareous soils in semiarid CearÃ, with emphasis on the study of pedogenetic changes provided by this practice. The areas chosen for study are located in Chapada do Apodi located in the city of Limoeiro do Norte - Ce. 8 amostrgens were performed in each area (in the irrigated area and the area outside and adjacent to the pivot). Subsequently, in each of the areas, trenches were opened to perform the morphological descriptions and collected soil samples for physical characterization, chemical, mineralogical and micromorphological. The results indicate significant differences have occurred in the irrigated area compared to non-irrigated area, and verified the increased dissolution of CaCO3 and increased levels of calcium, sodium and phosphorus. Furthermore, the flooded soil has changed its physical characteristics, and found an increase in density of particles decreased permeability of the soil air and the formation of pores less continuous. The analysis results showed that the profiles of 23 years of irrigation had effect on irrigated soil, making it more evolved in comparison to non-irrigated, it was verified by the results obtained in morphology with increasing soil thickness in physics with a lower silt / clay ratio and higher clay content in soil, mineralogy with evidence of increased neoformation of kaolinite and interstratified minerals, in micromorphology with the highest degree of pedalidade. The irrigated soil was classified as Chernosol by presenting chernozÃnico horizon followed by an incipient B horizon and possess high activity clay.

The rate of biodegradation of hydrocarbon contaminated soils can be studied using the radiocarbon (14C) content of CO2 efflux from the ground surface over an impacted area.14C is used as a tracer to distinguish modern 14C CO2 from natural respiration processes and 14C depleted CO2 derived from petroleum degradation. Studies have shown that this analysis provides reliable, quantifiable data and an effective means of correcting for background CO2 which may present some natural depletion from older subsurface organics. The study area for this project is a remote community in Northern Yukon where organic rich sediments overlying continuous permafrost are contaminated by diesel oil. An objective of this study was to evaluate the use of 14C to quantify background CO2 in permafrost soils with abundant, older labile organics. A second objective was to test a new sampling technique to facilitate sample shipment from remote sites, which traps soil CO2 in small sealed exetainers as a solid barium carbonate. Data obtained from established radiocarbon sampling procedures and this new novel approach were shown to be comparable and reproducible. This technique facilitated both sample collection and shipment as well as analysis by accelerator mass spectrometry (AMS), allowing for rapid, efficient sampling techniques to be deployed in remote areas. Results of this study show the carbonate method to be an economical and effective sampling method, and used at the Old Crow site, demonstrated that under current climate conditions, older organics in the subsurface do not confound the use of 14CO2 for source zone biodegradation assessment at this hydrocarbon impacted permafrost site.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Agrárias, Programa de Pós-Graduação em Aquicultura, Florianópolis, 2014.<br>Made available in DSpace on 2015-02-05T20:29:10Z (GMT). No. of bitstreams: 1 328869.pdf: 709204 bytes, checksum: 857a7255d9a4b7574c04aea67d2510ed (MD5) Previous issue date: 2014<br>O presente trabalho teve por objetivo avaliar a reatividade e o poder neutralizante de diferentes fontes de carbonato de cálcio comercializados no Estado de Santa Catarina (SC) para o aumento da alcalinidade da água doce e para a correção da acidez dos solos em aquicultura. Foram testadas três marcas de calcário durante 48 dias com três repetições cada, incubados em solos com baixos valores pH obtidos na cidade de Lages no Estado de SC, usando a metodologia SMP, sendo que a eficiência dos corretivos foi determinada com base no Poder Neutralizante (PN), Reatividade (RE) e Poder Relativo de Neutralização Total (PRNT). A alcalinidade foi determinada através do processo de neutralização acido/base usando ácido sulfúrico (H2SO4) 0.01 mol/L, e com o uso de indicadores ácido-base. Foram observadas diferenças significativas (P<0,05) no PN, RE e PRNT entre os corretivos, ou seja, os corretivos apresentaram diferenças na capacidade potencial de neutralizar a acidez dos solos e na velocidade de ação quando em contato com o solo. O pH do solo incubado com estes corretivos teve diferenças significativas (P<0,05). O corretivo A permitiu elevar o pH do solo de 4,2 para aproximadamente 7,0 num período de 8 dias, o corretivo B dentro de 32 dias e o corretivo C num período 48 dias. A origem e o tipo de calcário mostraram diferenças na velocidade e capacidade de elevar o pH ao nível desejado, por outro lado, os produtos A, B e C foram capazes de produzir um aumento significativo na alcalinidade da água, porém não diferentes em termos estatísticos, sendo que o produto A produziu uma alcalinidade significativamente menor que os demais. As três marcas de corretivos comercializados no Estado de SC demonstraram a possibilidade para corrigir a acidez solos e elevação da alcalinidade, embora duas marcas possam ser indicadas na calagem e correção da alcalinidade da água em viveiros de aquicultura.

Cette étude présente les architectures et la dynamique sédimentaire de la pente carbonatée au nord de Little Bahama Bank (Bahamas) à partir des données de sondeur multifaisceaux, de sondeur de sédiments (Chirp) et de sismique multitraces Haute Résolution (HR) issues de la mission Carambar 1(2010). Une analyse morpho-sédimentaire de surface permet de définir les grands domaines physiographiques et les éléments architecturaux de la pente et précise la répartition spatiale des sédiments dans le contexte actuel de haut niveau marin relatif. Elle révèle une pente dominée par de la boue de périplate-forme avec différents niveaux d’induration et entaillée par des glissements et des canyons sous marins.La variabilité spatiale du transfert de boue depuis la plate-forme vers la pente, couplée à l’évolution latérale de l’intensité du courant des Antilles est à l’origine de grandes différences morphologiques d’est en ouest. Dans la partie occidentale, la pente est environ deux fois plus étendue que dans la partie orientale,elle s’apparente à un système progradant. La pente orientale, quant à elle, est marquée par des processus de bypass. En effet, cette partie est caractérisée par de nombreux canyons sous-marins se poursuivant par des sillons distributaires alimentant des zones de dépôts distales confinées. Une étude intégrée permet la caractérisation à haute résolution des glissements et des canyons et la proposition d’un modèle déformation. Ces éléments architecturaux sont initiés par des déstabilisations intra-pente et leur évolution est contrôlée par des épisodes d’érosion régressive, la sédimentation pélagique et les écoulements gravitaires boueux. Enfin, une analyse sismo-stratigraphique permet de reconstituer l’évolution tectono-sédimentaire de la pente de l’Albien à l’Actuel en lien avec le contexte géodynamique des Caraïbes, l’eustatisme et la production carbonatée sur la plate-forme<br>This study focuses on the architectures and the sedimentary dynamic of a carbonate slope located on the northern part of Little Bahama Bank (Bahamas) using a dataset composed of multibeam echo sounder,subbottom profiler (Chirp) and High-Resolution (HR) multichannel seismic collected during the Carambar 1cruise (2010). A morpho-sedimentary surface analysis defines the physiographic domains and the architectural elements of the slope and investigates the spatial distribution of sediments in the context of the current sea-level highstand. It reveals a slope dominated by periplatform ooze with several levels of induration and incised by numerous slides and submarine canyons. The spatial variability of off-bank transport, combined with the lateral variability of the Antilles Current intensity, are at the origin of a morphological evolution from west to east in the study area. In the western part, the slope is around twice as large as the eastern part and can be considered as a prograding system. The eastern slope is marked by bypass processes. Indeed, numerous submarine canyons are visible on the seafloor and are connected to several shallow distributary furrows feeding confined depositional areas. An integrated study allows a high resolution characterisation of slides and submarines canyons and enables us to propose a model of formation. These architectural elements are initiated by intra-slope destabilisations and their evolution is controlled by phases of retrogressive erosion,pelagic sedimentation and muddy gravity flows. Finally, a seismo-stratigraphic analysis allow to reconstitutethe tectonic and sedimentary evolution of the slope since the Albian to the present-day by establishing a link with the geodynamic context of Caraïbes, relative sea-level changes and the carbonate production on the platform

Le premier objectif de cette étude est d'examiner la dégradation abiotique de paroi végétale de paille de blé dans un milieu simulant les sols de craie où semblent régner des conditions physico-chimiques favorables pour que des processus de dégradation abiotiques soient efficaces. Le second objectif est d'examiner les possibilités d'incorporation covalente de pesticides aux lignines au cours de leur oxydation par les métaux. La macération de la paille dans le carbonate induit une déstructuration de la paroi végétale qui se traduit par une modification de la composition des lignines en structures b-o-4 et par une modification du fractionnement des constituants pariétaux. Celles-ci résulteraient de la solubilisation d'une fraction de lignine qui favoriserait le gonflement des hémicelluloses en milieu alcalin et qui modifierait ainsi les interactions entre les différents constituants pariétaux ainsi que leur accessibilité aux réactifs. La présence de cuivre induit quelques perturbations supplémentaires par rapport au carbonate dans l'organisation de la paroi en diminuant l'extractibilité des constituants pariétaux et en augmentant la quantité de structures b-O-4 analysées dans les lignines résiduelles. Ceci pourrait résulter à la fois d'une dépolymérisation des lignines résiduelles et d'une modification des interactions entre les différents constituants suite à la formation de complexes avec le cuivre. Enfin, la possibilité de couplage covalent entre des modèles de lignine avec différents pesticides a été examinée dans ces conditions. Le couplage covalent de l'isopropylaniline, métabolite de l'isoproturon a été montré lors de l'oxydation de l'alcool coniférylique par les métaux. Ce couplage dépend de la propriété nucléophile ou de la capacité des pesticides et modèles à générer des radicaux au cours de l'oxydation. Des couplages covalents entre l'isopropylaniline et les DHP peuvent être créés lors de l'oxydation sans exclure des phénomènes d'association et d'absorption.

Le but de ce travail a consiste a modifier la surface du carbonate de calcium par des organosilanes, en vue de son incorporation en tant que charge dans le polypropylene isotactique, et l'etude des proprietes du materiau resultant. Dans un premier temps, nous avons decrit la synthese de molecules bisilylees de type (eto)#3si-r-si(oet)#3, avec r = c#6h#4 et (ch#2)#n (n = 2, 6, 10, 14), et (eto)#2mesi-(ch#2)#6-sime(oet)#2. Dans un second temps, nous avons mis au point un pretraitement du carbonate de calcium par la silice, avant de le traiter par differents silanes selon le procede sol-gel. Nous avons caracterise les particules traitees par differentes methodes. Enfin, nous avons decrit l'incorporation de ces particules au polypropylene isotactique et l'etude des proprietes du materiau resultant.

Cette thèse concerne l'étude expérimentale et la modélisation de la déformation des roches polyminérales par le mécanisme de la dissolution cristallisation sous contrainte. D'une part, il est montré qu'une augmentation de la proportion de grains peu solubles dans une roche diminue la résistance à la déformation. Cela indique une compétition entre deux mécanismes: d'une part la dissolution sous contrainte aux contacts des grains accélère la déformation, et d'autre part la cicatrisation de ces contacts inhibe la dissolution et ralentit le fluage. D'autre part, il a été réalisé des expériences de poinçonnement de monocristaux de calcite en présence de fluide. La vitesse de déformation de la calcite est de deux ordres de grandeur plus élevée que prévu par la théorie. Cet effet peut être expliqué par le développement de microfissures dans la calcite au contact du poinçon. Ces résultats sont appliqués au comportement des sites de stockage de déchets radioactifs et de séquestration du CO2.

Acid deposition forms when emission-derived sulfur dioxide and nitrogen oxides interact with precipitation and was particularly severe in the northeastern US. Effects of acid deposition include declining soil quality due to low pH and base cation leaching, which subsequently altered the composition of soil solution, ground water (GW) and eventually stream water. Because of the high buffering capacity of carbonates, watersheds underlain by carbonate rich rocks have received limited attention in acid deposition studies, however, carbonate weathering by strong anthropogenic acids can increase atmospheric CO2 levels. Emission reductions due to the Clean Air Act and Amendments has led to a substantial reduction of acid deposition and many ecosystems are now recovering and stream water exports contain lower concentrations of acid anions and base cations. However, the effects of recovery on watershed soil, soil solution, and GW composition, which potentially varies with landscape position, are not well constrained. The objective of this study was therefore to investigate links between soils and water composition in a watershed with important carbonate contents in the underlying rock, the Sleepers River Research Watershed (SRRW), using long-term datasets that span the recovery period. Temporal trends (1991-2015) for acid anions (sulfate and nitrate), pH, base cations (Ca, Na) and Si were investigated for stream water and trends with time, depth, and landscape position (hilltop, hillslope, and riparian zone) for the same solutes were assessed in GW and soil solution (2004-2013). Furthermore, soil elemental composition and mineralogy in archived (1996) and modern (2017) soil samples were analyzed to investigate changes in soil composition due to base cation leaching and carbonate weathering with time and landscape position. Results indicate that SRRW is indeed recovering from acidification as evidenced by declining sulfate content and rising pH in stream water, GW, and soil solution. Additionally, Ca typically derived from carbonate weathering decreased progressively with time in GW and showed signs of decreasing in soil solution at various landscape positions due to reduced leaching. However, Ca in stream water shows slight increases, likely due to Ca released from riparian soil stores. Spatial heterogeneity is especially pronounced in headwater catchments with steep topography as evidenced by changes in solution and soil composition along hillslopes. In addition to the paper submitted for publication (Chapter 2) to Frontiers in Earth Science – Biogeochemistry this thesis includes i) a background and literature review to inform the reader on pertinent topics, ii) an appendix containing additional soil data with figures, iii) and an appendix with additional aqueous phase data with figures.

Um experimento em casa de vegetação, foi conduzido objetivando comparar os efeitos da aplicação de sulfato de cálcio, fosfogesso, e carbonato de cálcio sobre a alteração das propriedades da fase sólida e liquida de amostras de subsolo de dois latossolos vermelho-amarelos álicos, dois latossolos roxos ácricos e um latossolo vermelho escuro álico do estado de São Paulo. Avaliaram-se os efeitos dessas alterações sobre o crescimento e a absorção de água e nutrientes pelo milho (Zea mays L.). Utilizou-se uma técnica de raiz bipartida vertical, em que quatro plantas de milho foram cultivadas inicialmente em um recipiente contendo 130 g de uma amostra de solo fértil. Quinze dias após a germinação, removeu-se o recipiente e o bloco de terra com as plantas foi introduzido em um vaso preenchido com 2 dm3 de amostra de subsolo, que recebeu um dos seguinte tratamentos: sem corretivo, sulfato de cálcio, fosfogesso e carbonato de cálcio, aplicados na dose de 10 mmo.dm- 3 de terra, além de 56 mg de N e 78 mg de K. Passados mais dezenove dias, as plantas foram colhidas e o subsolo contido nos vasos foi amostrado para determinações do teor de água e do comprimento radicular e para a realização de análise química. O sulfato de cálcio e o fosfogesso aumentaram o pH em cloreto de cálcio e o teor de Ca2+ trocável e reduziram o Al3+ trocável e o H+ + Al3+, mas em menor proporção que o carbonato de cálcio. Não houve diferença significativa entre o sulfato de cálcio e o fosfogesso quanto a esses efeitos. Os valores de pH em água diminuíram devido ao efeito do sal na medida do pH. As amostras de subsolo utilizadas apresentaram severas restrições ao desenvolvimento do sistema radicular do milho. Com a adição dos corretivos o comprimento de raízes aumentou em até 194 % devido à correção da deficiência de cálcio e/ou redução da toxicidade do alumínio. O carbonato de cálcio reduziu a atividade do Al3+ pelo aumento do pH. Nos latossolos ácricos e no latossolo vermelho escuro álico, o sulfato de cálcio e o fosfogesso também provocaram a redução da atividade de Al3+ como resultado do aumento da força iônica da solução e formação do par iônico AlS04 +. No caso do fosfogesso, a formação de complexos de Al com F (AlF2+ e AlF2 +) foi a principal causa da redução da atividade do Al3+. Já nos latossolos vermelho-amarelos álicos, o aumento do comprimento de raízes nos tratamentos com sulfato de cálcio e fosfogesso deveu-se, provavelmente, ao efeito do cálcio em reduzir a toxicidade do alumínio, uma vez que a atividade do Al3+ foi aumentada. A produção de matéria seca do milho aumentou com a aplicação dos corretivos em todos os solos. Nos latossolos ácricos e no latossolo vermelho escuro, o efeito do calcário foi inferior ao efeito do sulfato de cálcio e do fosfogesso devido à menor concentração de nutrientes na solução. Nos latossolos vermelho-amarelos álicos não houve diferença entre os corretivos. O sulfato de cálcio e o fosfogesso foram tão eficazes quanto o carbonato de cálcio em favorecer a absorção de nitrogênio e potássio do subsolo<br>not available