L'atmosphère terrestre a subi, au cours de son histoire précoce, de très violents changements dans sa composition chimique. L'émergence des premiers êtres vivants photosynthétique a provoqué la mise en place et la modification des grands cycles biogéochimiques. L'usage des isotopes comme traceurs des processus physico-chimiques actifs pendant ces périodes s'est développé depuis les années 80. L'observation de compositions isotopiques anormales dans certaines molécules atmosphériques (ozone notamment), similaires à celles observées dans les météorites par Clayton (1973), pose question. De nombreuses hypothèses ont été proposées pour expliquer ce phénomène "anormal". L'objectif principal de cette thèse de doctorat est de développer, par l'expérimentation, l'étude d'un certain nombre de réactions en phase plasma du point de vue isotopique. Seront particulièrement étudiées des réactions appelées réactions à trois corps de formation de l'ozone, où la formation d'un complexe intermédiaire excité entre en jeu dans les mécanismes de génération de ces fractionnements isotopiques anormaux. / The Earth's atmosphere has undergone, during its early history, very violent changes in its chemical composition. The emergence of the first photosynthetic living beings has led to the establishment and modification of major biogeochemical cycles. The use of isotopes as tracers of active physico-chemical processes during these periods has been developed since the 1980s. The observation of abnormal isotopic compositions in certain atmospheric molecules (ozone in particular), similar to those observed in meteorites by Clayton (1973), raises questions. Many hypotheses have been proposed to explain this "abnormal" phenomenon. The main objective of this doctoral work is to develop, through experimentation, the study of plasma reactions from an isotopic point of view. In particular, ozone formation third-body reactions, where the formation of an excited intermediate complex is involved in the mechanisms of generating these abnormal isotopic fractionations, will be studied.

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Cette thèse a pour but d’identifier et de préciser les processus biotiques et abiotiques qui contrôlent le comportement du Ca et plus spécifiquement le fractionnement des isotopes du Ca à l’interface géosphère-biosphère-hydrosphère en combinant différentes études expérimentales (hydroponiques et microcosmes). Les résultats obtenus lors des expérimentations hydroponiques ont permis d’identifier 3 niveaux de fractionnement des isotopes du Ca au sein des végétaux, ces 3 niveaux de fractionnement sont induits par des mécanismes physico-chimiques qui enrichissent les organes de végétaux en 40Ca.Les résultats des expérimentations hydroponiques montrent également que l’évolution de la composition isotopique du Ca de la solution nutritive et des plantes suit une loi de fractionnement des isotopes du Ca à l’équilibre (αplantes/solution nutritive = 0,99858). Les expérimentations abiotiques en microcosmes, quant à elles, indiquent que la dissolution de l’apatite par des acides organiques ou inorganiques n’influence pas la signature isotopique en Ca de la phase dissoute résultante. À l’inverse, lors des expérimentations biotiques en microcosmes, seule l’action combinée des racines de pins et des bactéries sur un substratum d’apatite enrichit la solution qui percole en 44Ca de 0,22‰. / The aim of this thesis is to identify and to specify biotic and abiotic processes affecting the Ca behavior and specifically the Ca isotope fractionation at the geosphere/biosphere/hydrosphere interface by combining different experimental studies (hydroponic and microcosm).Results of hydroponic experiments allow to identify three Ca isotopic fractionation levels, which are driven by physico-chemical mechanisms and enrich the plant organs in the light 40Ca isotope. Moreover, the evolution of Ca isotopic composition of nutrient solution and plants follow an equilibrium law (αplants/nutrient solution = 0.99858).Abiotic column experiments show no Ca isotopic fractonation during apatite disolution, whatever the nature of the acid (mineral or organic). At the opposite, during biotic microcosm experiments, only the combined action of roots of scots pines and bacteria on apatite substratum enrich the percolate solution in heavy 44Ca of 0.22‰.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-03-14T13:09:52Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE_DETERMINAÇÃO DO CARBONO E NITROGÊNIO ORGANICO PARTICULADO EM AMBIENTES OCEÂNICOS E ESTUARINO - COSTEIRO, NA REGIÃO N~1.pdf: 3127471 bytes, checksum: 07f07e56cbb161e91a0b19e2387b5734 (MD5) / Made available in DSpace on 2017-03-14T13:09:52Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE_DETERMINAÇÃO DO CARBONO E NITROGÊNIO ORGANICO PARTICULADO EM AMBIENTES OCEÂNICOS E ESTUARINO - COSTEIRO, NA REGIÃO N~1.pdf: 3127471 bytes, checksum: 07f07e56cbb161e91a0b19e2387b5734 (MD5) Previous issue date: 2016-07-14 / CAPES / O objetivo principal da presente tese constitui em agregar informações ao conhecimento sobre a fração orgânica do material em suspensão na região oceânica- costeira - estuarina do litoral de Pernambuco e na região costeira adjacente, principalmente no que se refere às suas concentrações, avaliando a distribuição do COP e NT. Em função da sua importância e estudos relacionados ao material em suspensão serem escassos para o carbono e nitrogênio nessas regiões. A tese é apresentada como um conjunto de capítulos interligados, nos quais foram apresentados resultados da distribuição do COP e NT nas plumas dos rios Capibaribe e Jaboatão e o arquipélago de Fernando de Noronha, com relativamente pouca influência humana, e foi escolhida como área de controle. A exportação de matéria orgânica via fluxo estuarino, ficou definida pelas medianas do Carbono Elementar de (2,04% e 0,97%) e Nitrogênio Elementar de (0,63% e 0,24%) e razão C/N de (6,60 e 9,30) nas plumas do Capibaribe e Jaboatão respectivamente. A análise de componentes principais aplicada aos dados sugeriu que os altos índices pluviométricos e o material carreado pelo fluxo fluvial para região costeira influenciaram a distribuição dessas frações e que tais diferenças podem resultar das diferentes cargas de ação antrópica e mecanismos de transporte estuário – região costeira revelando a complexidade da distribuição da matéria orgânica nestes ambientes. No segundo capítulo-artigo estudo caracterizou a matéria orgânica em função das razões elementares e isotópicas δ13C, δ15N, C/N do material particulado em suspensão na água superficial em 21 pontos amostrais sendo 12 no estuário do rio Capibaribe e 9 no estuário do rio Jaboatão. Os maiores valores de δ13C, δ15N, C/N (-17,75‰, 23,71‰ e 13,45‰) no Capibaribe e, (-21,97‰, 27,30‰ e 14,74‰) no Jaboatão, respectivamente. Os valores encontrados sugerem que uma grande parte da matéria em suspensão dos rios em estudo, se origina a partir de entradas de efluentes com alto teor de matéria orgânica, como também que a MO exportada pelos rios é fortemente influenciada pelo seu elevado estado de eutrofização, com acentuada produção autóctone. Nos estuários superiores os valores empobrecidos de 13C indicam maior presença de material tanto de origem continental quanto de origem mista. É também observado que δ13C e a razão C/N não são correlacionados no estuário do Capibaribe e estes resultados sugerem que existem áreas no estuário de preferência, fontes de matéria orgânica sob a influência tanto de autóctones (estuário inferior) como de alóctones (estuário superior). O terceiro e último capítulo - artigo ocorreu na região costeira de PE e foram agregadas as frações COP e NT à fração de COD, as quais não apresentaram correlação, indicando que elas não tenham a mesma fonte, destacando a influência alóctone para o aumento dessas frações e assim os efeitos de influencia do rio Capibaribe nas águas oligotróficas costeiras. / The main objective of this thesis is to add information to the existing knowledge of the organic fraction of suspended matter in the oceanic-coastal-estuarine region of the coast of Pernambuco, Brazil and the adjacent coastal zone, mainly in regard to its concentrations, by evaluating the distribution of POC and NT. In spite of the importance of this topic, studies on suspended matter for carbon and nitrogen are scarce in these regions. The thesis is presented as a set of interrelated chapters that contain the results of POC and NT distribution in the plumes of rivers Capibaribe and Jaboatão. The Fernando de Noronha Archipelago was chosen as a control area because of the minimal human influence in this region. The export of organic matter through estuarine flow was defined using the medians of elemental carbon (2.04% and 0.97%) and elemental nitrogen (0.63% and 0.24%), and C/N ratio (6.60 and 9.30) in the Capibaribe and Jaboatão plumes, respectively. The principal component analysis applied to the data suggests that the high rainfall and the matter carried by the river flow to the coastal region influence the distribution of these fractions. The analysis also suggests that the detected differences can be caused by different charges of human action and estuarycoastal mechanisms of transport, thus revealing the complexity of the distribution of organic matter in these environments. In the second chapter of the article, organic matter was characterised on the basis of elementary and isotopic ratios δ13C, δ15N, and C/N of the suspended particulate matter in surface water at 21 sampling points, of which 12 were in the estuary of river Capibaribe and 9 in the estuary of river Jaboatão. The highest values of δ13C, δ15N, and C/N (-17.75‰, 23.71‰, and 13.45 ‰) in Capibaribe and (-21.97‰, 27.30‰, and 14.74 ‰) in Jaboatao, respectively. The values found in this study suggest that a large proportion of suspended matter from the rivers originates from effluent inputs with high organic matter content. Also, the OM exported by the rivers is heavily influenced by a high state of eutrophication, with pronounced autochthonous production. In the upper estuary, the impoverished values of δ13C indicate a greater presence of matter of continental origin and of mixed origin. It was also observed that δ13C and C/N ratio are not correlated in the estuary of the Capibaribe, which suggests that there are areas at the estuary of preference where sources of organic matter are under the influence of autochthonous (lower estuary) or allochthonous (upper estuary) contributions. The third and final chapter-article occurred in the coastal zone of PE. Here, the fractions of POC and NT were added to the fraction of DOC and showed no correlation, which indicates that they do not share the same source. Moreover, this finding highlights the influence of allochthonous contributions to the increase of these fractions and the consequent effects of the influence of Capibaribe river in coastal oligotrophic waters.

This study presents results from stable isotope analyses of a modern stalagmite and three soda straw stalactites from Kapsia Cave, the Peloponnese, Greece. The resulting values from the stalagmite are put into context of local meteorological data, as well as previous research from Kapsia Cave. The potential for using soda straw stalactites as complementary climate archives on shorter time scales on the Peloponnese is also explored. The isotopic values in the stalagmite confirm a strong link to the amount effect on an annual scale. On a seasonal scale, variations in the isotopic signal can be detectedas a result of i.e. increased cave air temperature in summer. The stable isotope values in the soda straw stalactites largely correspond to previous isotopic measurements in Kapsia Cave. The trend of the isotopic carbon signal in two of the straws also strengthens earlier theories suggesting a link to CO2 concentrations in the external atmosphere. Soda straws are, thus, encouraged for use in future climate studies, although the sampling method should be further explored. The results of this study contribute to an increased understanding of Peloponnesian speleothems in relation to environmental processes and new insights are suggested into the use of soda straw stalactites as climate archives.

L’azote et les gaz rares présents dans les astéroïdes, les comètes et les atmosphères planétaires sont piégés dans de la matière organique et ont des compositions chimiques qui sont différentes de celle du Soleil, représentatif du gaz primordial à partir duquel les différents objets du système solaire se sont formés il y a 4,5 milliards d’années. Au cours de cette thèse, des synthèses de matière carbonée à partir d’un mélange de gaz ont été réalisées dans un plasma appelé le Nébulotron, afin de mieux comprendre les processus à l’origine des compositions de l’azote et des gaz rares présents dans les météorites. Les caractéristiques de la matière organique ainsi que la composition des gaz rares piégés dans les météorites sont relativement bien reproduites dans les expériences, mais pas celle de l’azote. Ces résultats expérimentaux permettent de proposer des mécanismes clé à l’origine des compositions des éléments volatils présents dans les objets du système solaire. / Nitrogen and noble gases present in asteroids, comets or planetary atmospheres are trapped in organic matter and bear a composition that is different from the composition of the Sun, which is representative of the primordial gas from which the different objects in the solar system were formed 4.5 billion years ago. During this thesis, experimental syntheses of organic matter from gas mixtures in a plasma setup called the Nebulotron were performed in order to better understand the processes responsible for this chemical difference between the meteorites and the Sun for nitrogen and noble gases. The characteristics of the organic matter and the signature of the noble gases trapped in meteorites are relatively well reproduced in the experiments, whereas the composition of nitrogen is not. These experimental results give hints about the key mechanisms that are responsible for the variations of the volatile elements composition in the solar system objects.

Freshwater lakes constrain its methane (CH4) emissions through CH4 oxidation. CH4 includes three carbon (C) isotopes; the stable isotopes 12C,13C and the unstable and more uncommon isotope 14C. Methanotrophs (i.e. methane oxidizing bacteria) oxidize the lighter isotope more rapidly. Changes in relative isotopic composition can therefore be used to calculate how much CH4 is oxidized in a system. This study investigates an annual CH4 oxidation in a freshwater lake. Water samples and bubbles of CH4 gas were collected once a month, from March to November, in lake Gundlebosjön. The CH4 gas was separated from the water samples with a headspace extraction technique. The concentration and isotopic composition of CH4 was analyzed in a cavity ring down spectrometer. The isotopic data was used in two mathematical models, based on open-steady state and closed systems. It was found that the stable isotope method to estimate CH4 oxidation was only useful during periods when clear concentration and isotope differences could be observed in the water column. CH4 oxidation could only be estimated in the water column in August, and in the surface layer in June and July. / Utsläppen av metan (CH4) från sötvattensjöar begränsas genom CH4 oxidation. Det är två stabila kolisotoper som dominerar i CH4; 12C och 13C. Den ostabila kolisotopen 14C finns även i CH4, men den är mer ovanlig i naturen. Metantrofer (metanoxiderande bakterier) oxiderar den lättare kolisotopen snabbare. Förändringar i isotopsammansättningen kan användas för att beräkna hur mycket CH4 som oxideras i ett system. Denna studie undersöker en årlig CH4 oxidation i en sötvattensjö. Vattenprover och bubblor av CH4-gas samlades en gång i månaden, från mars till november, i Gundlebosjön. CH4 gasen separerades från vattenproverna med en ”headspace extraction” teknik. Koncentration och isotopsammansättningen av CH4 analyserades i en ”cavity ring down spectrometer”. Isotopdata användes i två matematiska modeller, baserade på öppet-stabilt tillstånd och stängt system. Den stabila isotopmetoden för att uppskatta CH4 oxidation var endast användbar under perioder då tydliga skillnader i koncentrationen och isotopsammansättningen kunde observeras i vattenpelaren. CH4 oxidation kunde endast uppskattas i vattenpelaren i augusti, och i vattenpelarens ytskikt i juni och juli.