Ocean uptake of anthropogenic CO2 causes ocean acidification, a secular, global-scale decline in the pH of seawater. In order to better understand the implications of contemporary acidification for marine organisms and ecosystems, there is a need to better characterise natural variability in carbonate chemistry. In this thesis, climatological seasonal variability of sea surface pH and aragonite saturation state (OmegaA) in the open ocean is indirectly derived from other parameters of the marine CO2 system, namely total alkalinity (TA) and seawater pCO2/fCO2 (pCO2sw/fCO2sw). New monthly sea surface TA, fCO2sw and temperature climatologies are developed for this purpose, utilising newly-released observational synthesis products (PACIFICA for TA and SOCAT v2 for fCO2sw). Two versions of the new SST climatology are developed, referred to as upper and lower SST (USST and LSST), to test sensitivity to the depth range of the input observations. Annual ranges are generally found to be larger for the USST climatology, derived using observations from the upper 2 m, compared to LSST (which is based on deeper observations). Further, a seasonal cycle is found in the monthly average of the differences between these climatologies north of 30 degN, perhaps partly due to seasonal variation in near-surface stratification. The USST seasonal ranges are also found to be generally larger than in two previous SST climatologies, however, difference in the depth distribution of the input measurements is unlikely the main cause. The new monthly sea surface TA climatology extends coverage into the Nordic seas, excluded from previous climatologies. TA seasonality is found to be small outside of regions with large seasonal ranges in salinity. Large seasonal ranges in salinity and TA are found beneath the Intertropical Convergence Zone, in the Antarctic seasonal sea ice zone and in the western Greenland Sea. Non-salinity driven TA seasonality is found to be large in the Gulf of Alaska, eastern equatorial Pacific and western Greenland Sea. Compared to the Lee et al. (2006) TA climatology, substantially lower annual means and seasonal ranges are found for the subarctic Pacific, a region with greatly improved coverage courtesy of PACIFICA. The pH/OmegaA climatologies derived in the final chapter suggest pH seasonality is predominantly temperature driven in the subtropics and mainly driven by variation in salinity normalised dissolved inorganic carbon (sDIC) in the subpolar north Atlantic, western subarctic Pacific and Southern Ocean. Salinity variation is found to only exert a strong influence on pH seasonality in the western Greenland Sea. Climatological seasonal pH ranges are found to be mostly small in the tropics (<0.05), moderate in the subtropics (0.05-0.10) but very large (>0.1) in parts of the Ross, Weddell, Irminger and Iceland Seas and western subarctic Pacific gyre. OmegaA seasonality is found to be predominantly sDIC-driven everywhere except in the western Greenland Sea, with temperature variation generally being of modest influence. Seasonal cycles of pH and OmegaA are found to be in anti-phase where pH is mainly thermally driven and in-phase where pH is mainly sDIC-forced (both pH and OmegaA vary inversely with DIC). Comparison is made between the primary new pH/OmegaA climatology and various open ocean carbonate chemistry time-series. The climatology captures the general form of the climatological seasonal cycles of pH and OmegaA from the time-series, although with some differences in phasing and seasonal range. Analysing the time-series for long-term trends, I find that inter-decadal anthropogenic CO2 uptake driven pH and OmegaA declines can be modulated by trends in temperature, salinity or sTA. Investigation is also conducted into how the amplitude of pH and OmegaA seasonal cycles might change by 2100 for a subpolar and subtropical time-series. Under a high CO2 emissions scenario, the seasonal range of pH is found to be strongly enhanced for the subpolar time-series and moderately reduced for the subtropical time-series, with both being due to changes in seawater buffer capacity. / Graduate / 0425 / 0415 / robdj87@hotmail.com

This thesis focuses on the vibrational spectroscopy of the aragonite and vivianite arsenate minerals (erythrite, annabergite and hörnesite), specifically the assignment of the spectra. The infrared and Raman spectra of cerussite have been assigned according to the vibrational symmetry species. The assignment of satellite bands to 18O isotopes has been discussed with respect to the use of these bands to the quantification of the isotopes. Overtone and combination bands have been assigned according to symmetry species and their corresponding fundamental vibrations. The vibrational spectra of cerussite have been compared with other aragonite group minerals and the differences explained on the basis of differing chemistry and crystal structures of these minerals. The single crystal spectra of natural erythrite has been reported and compared with the synthetic equivalent. The symmetry species of the vibrations have been assigned according to single crystal and factor group considerations. Deuteration experiments have allowed the assignment of water vibrational freque ncies to discrete water molecules in the crystal structure. Differences in the spectra of other vivianite arsenates, namely annabergite and hörnesite, have been explained by consideration of their differing chemistry and crystal structures. A novel approach to the assignment of site occupancy of ions in the erythrite - annabergite solid solution has been reported. This approach has utilised vibrational spectroscopy, in conjunction with careful consideration of the crystal structures of the minerals. It has been shown that in the erythrite - annabergite solid solution Coprefers metal site 2 contrasting nickel which prefers site 1. This study in conjunction with other studies has yielded the trend that the more electronegative metal prefers to occupy site 1, with the least electronegative metal preferring to occupy site 2. Fundamentally this thesis has increased the knowledge base of the spectroscopic properties of the aragonite and the vivianite minerals. The site occupancy of metal ion substitutions in solid solution series of the vivianite group of minerals has been further enhanced, with novel method of studying the site occupancy of ions in solid solutions has been developed. A detailed knowledge and understanding of factor group analysis applied to the study of minerals has been achieved.

Made available in DSpace on 2014-10-09T12:35:56Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:32Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:35:56Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:32Z (GMT). No. of bitstreams: 0 / A forma isomórfica predominante nos biominerais (casca de ostra, coral, madrepérola e concha) estudados foi a aragonita. Contudo, o surgimento da fase calcita deu-se à temperatura de 500°C a uma taxa de aquecimento de 10°C/s para todas as amostras; e para a amostra de coral, à temperatura de 400°C, independente da taxa de aquecimento. O elemento mais abundante nas amostras de biominerais foi o Ca na forma de CaO e para os silicatos (tremolita, diopsídio e rodonita), o Si na forma de SiO. O elemento traço mais presente nas amostras de biominerais foi o Fe. A análise de ressonância paramagnética eletrônica mostrou as linhas de Mn2+ nas amostras de coral e madrepérola, antes da irradiação. Para amostras irradiadas, os defeitos encontrados foram os radicais CO2-, CO33-, CO3-, SO2-, SO3-, e num intervalo de g entre 2,0010 e 2,0062. Na análise por absorção óptica dos biominerais foram encontradas transições devido à presença de Mn nas amostras. Foi observado um pico termoluminescente (TL) em aproximadamente 140°C para os biominerais e em 180°C para os silicatos, cuja intensidade depende diretamente da dose. Para amostras expostas a diferentes tipos de radiações, o pico TL ocorre em temperaturas mais baixas. Para as curvas dose-resposta obtidas para esses materiais, foi possível determinar um intervalo de linearidade para o qual a sua aplicação em dosimetria de doses altas se torna possível. Levando-se em consideração o tipo de radiação, dentre os biominerais e os silicatos, obteve-se a menor dose detectável (40mGy), para a radiação gama em amostra de casca de ostra utilizando-se a técnica de medição de luminescência opticamente estimulada (LOE). Para radiação beta, as amostras de tremolita e diopsídio obtiveram a menor dose detectável (60mGy). No geral, obteve-se uma boa reprodutibilidade para as amostras, utilizando-se as técnicas TL, LOE e emissão exoeletrônica termicamente estimulada (TSEE) para as radiações alfa, beta e gama. Portanto, pode-se concluir que as amostras caracterizadas neste trabalho podem ser utilizadas como detectores/dosímetros de doses altas. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Carbonate geochemistry plays an important role in understanding environmental conditions during the time of precipitation. The studies for this dissertation research were focused on carbonate precipitation and crystallization in different chemical and physical environments. The first project aimed to precipitate aragonite at low oxygen levels to identify a correlation between partitioning of trace elements and anoxic and suboxic conditions. The second study focused on the precipitation of amorphous calcium carbonate in varying magnesium concentrations to determine the identity of crystalline material after transformation of ACC. Lastly, the third project was developed to understand transformation of CaCO3 polymorphs. Specifically, whether or not geochemistry is retained from one polymorph to the next. All projects could aid in development of paleoproxies to be used for determining past environmental and climatic conditions in the past.

Thermal waters in Karlovy Vary are characterized by carbonate sedimentation in places of their emergence. These sediments contain radium. Radium bond in every type of sinter (aragonite, calcite) has been investigated experimentally by acid sinter dissolution. It has been found out, that radium can join dissoluble fraction in both sinter types . The original hypothesis that radium can bond only aragonite-type of sinter has been refuted. Additional experiments have been processed using synthetic radiobarite. Present radium in radiobarite can be partly dissoluted using acids. If radium was incorporated in radiobarite (it is known from locality Vřídlo in Karlovy Vary and elsewhere) then maybe it would be partly dissoluted in experiments.

La datation absolue des archives climatiques est essentielle pour comprendre les mécanismes du climat. Cette étude a porté sur la fraction fine (<63 μm) riche en aragonite (adaptée à la datation U/Th) et sur les tests de foraminifères planctoniques (>150 μm) d'une carotte de sédiments marins de la Mer des Caraïbes couvrant le dernier million d'années, en utilisant une approche minéralogique et des traceurs géochimiques. Les objectifs sont : 1) évaluer le<br />synchronisme entre le δ18O et les âges absolus de deux fractions de tailles différentes et 2) reconstruire les paléoenvironnements de la zone. La minéralogie de la fraction fine est contrôlée par les changements du niveau marin à l'échelle glaciaire-interglaciaire. Les décalages temporels entre le δ18O et le 14C des deux fractions durant la Terminaison I sont en partie expliqués par un modèle de bioturbation. Les essais de datation U/Th sur la fraction fine des Terminaisons II et V ont montré une contamination par du Th non-radiogénique, nécessitant des développements analytiques. Les reconstitutions des variations de δ18O de l'eau de mer suggèrent une diminution de la salinité de surface à la fin de la Transition Mid-Pléistocène, associée à la position de l'ITCZ au niveau de la Mer des Caraïbes.

L'objectif de cette thèse était de synthétiser des particules de carbonate de calcium (CaCO3) poreuses pour applications industrielles comme charge dans du papier à cigarette, ainsi que pour l'encapsulation d’'arômes. Nous avons cherché à maîtriser les paramètres de synthèse pour obtenir de la vatérite de taille contrôlée. Nous avons étudié sa transformation à haute température et dans l’'eau, car ce polymorphe est métastable. La transition de phase vatérite/calcite a été étudié par DRX et imagerie par diffraction des rayons X cohérents qui permet d’accéder à l’'image en 3D des particules. Nous avons montré que la vatérite de taille 1 à 2µm présentant 20% de porosité peut être synthétisée de façon reproductible. Les particules préparées ont été introduites comme charge dans du papier à cigarette pour évaluer l’'impact de nouvelles formes de CaCO3 sur les propriétés physiques du papier ainsi que sur la réduction des certains composées nocifs contenus dans la fumée. Nous avons développé l’analyse conjointe de l’'absorption et de la diffraction des rayons X pour estimer la charge réelle introduite ainsi que la porosité des papiers. Nous avons démontré que l’'utilisation de CaCO3 sous forme des sphères poreuses permet d’'augmenter la diffusivité du papier et de réduire l’'émission de CO dans la fumée principale.L’encapsulation d'arômes par la co-cristallisation et l'inclusion moléculaire dans le carbonate de calcium a été aussi étudiée. Nous avons montré que CaCO3 peut être utilisé comme matrice d’'imprégnation d'arômes avec une efficacité d’'encapsulation de plus que 55%. Les particules aromatiques ont été après ajoutées dans le papier pour évaluation sensorielle. / The aim of this thesis was to synthesize porous calcium carbonate (CaCO3) particles for industrial applications as fillers for cigarette paper as well as a matrix for flavour encapsulation. We show that we can control the fabrication of porous particles of vaterite with a given size by tuning the parameters of synthesis. After the synthesis, the stability of vaterite in aqueous solution and at high temperature was studied. The phase transition was analyzed by XRD and coherent X-ray diffraction imaging that allows us to have a 3D-image of the particles. Finally, particles of 1-2 μm size with 20% porosity were reproducibly synthesized. Prepared vaterite particles were introduced as a filler in cigarette paper, with the goal to evaluate their impact on the physical properties of papers as well as on the reduction of some harmful compounds during the smoking. It was demonstrated that the use of vaterite can increase the diffusivity of paper and reduce the CO emission in the mainstream smoke. We also show that the use of X-ray absorption and diffraction can provide an estimation of the filler fraction and porosity of the papers in a non-destructive way. The encapsulation of flavours in CaCO3 particles was performed by co-crystallization and molecular inclusion. It was demonstrated that CaCO3 can be used as a matrix for flavour impregnation with more than 55% of encapsulation efficiency. Flavoured particles was added in paper for sensory evaluation. We shown that it is possible, to flavour the final product with flavoured calcium carbonate particles.

No description available.

Ce travail concerne l'évolution au cours du temps d'un système carbonaté sous l'effet de phénomènes de transport et de processus chimiques. La diagenèse carbonatée étudiée ici est la calcitisation, i.e., la transformation en calcite de l'aragonite constituant le squelette des coraux du genre Porites. En effet, le corail, qui sécrète son squelette en environnement marin peut subir au cours de son histoire une évolution au milieu sub-aérien suite à l'émersion du récif. Le squelette aragonitique alors confiné dans les lentilles d'eau douce, caractéristiques des aquifères coralliens, devient métastable et peut, à terme, être totalement calcitisé.<br />La compréhension de ces phénomènes est appréhendée par une approche pluridisciplinaire qui relève à la fois de la géologie (1) et de la physique des milieux poreux (2).<br />1. Géologie - Différents stades de calcitisation sont investigués sur des coraux fossiles datés de l'Holocène et du Pléistocène échantillonnés sur les terrasses soulevées de Nouvelle-Calédonie, Vanuatu et Wallis et Futuna (Pacifique Sud-Ouest). Les produits de la diagenèse sont observés et caractérisés par différentes techniques d'analyses (Diffraction de Rayons X, microscopie optique, imagerie de cathodoluminescence, spectroscopie Raman, Microscopie Electronique à Balayage, microsonde électronique...) pour argumenter l'origine de la calcite néoformée et identifier les processus mis en jeu, notamment l'implication ou non d'une étape de transport. <br />2. Physique des milieux poreux - Les données expérimentales révèlent l'existence d'hétérogénéités structurales à l'échelle de la lame mince. Pour expliquer ces hétérogénéités, on développe, à l'échelle microscopique, un modèle de transport réactif multicomposant incluant les processus représentatifs de la diagenèse du corail (diffusion de type traceur, migration, adsorption/désorption, réactions cinétiques et /ou à l'équilibre). Des simulations numériques préliminaires 1D sont présentées et discutées pour évaluer l'importance relative des phénomènes intervenant dans la précipitation de la calcite. Ce type de simulations numériques peut servir de point de départ à une procédure de changement d'échelles, permettant d'intégrer des paramètres supplémentaires (notamment plusieurs échelles de descriptions...). Ceci est illustré à l'aide de la prise de moyenne volumique, dans le cas d'un échantillon 3D de Porites subissant un processus de transport réactif fortement idéalisé.