Made available in DSpace on 2015-03-26T13:53:04Z (GMT). No. of bitstreams: 1 texto completo.pdf: 9391655 bytes, checksum: a8ab2eac1fae078c826bf566567e9ee1 (MD5) Previous issue date: 2008-02-08 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Oceanic islands are breeding places for several migratory species of birds whose their excrements are deposited on to the surface, besing subject to phosphatization. The occurrence of phosphatization has been related to specific environmental conditions and, for this reason, it is capable to indicate past environmental changes, associated to climate, oceanic currents, sea level changes, amongst others. Besides, it has strong influence in nutrients cycling and biological productivity of adjacent sea. Despite that, litte is known about this process, and how it can affect the formation of insular soils. Based on that, this work aimed at characterizing the phosphatization in São Pedro and São Paulo Archipelagos (ASPSP) and Fernando de Noronha (AFN), more specifically in Belmonte and Rata Islands, respectively. Samples of rocks and soils were collected in those two islands, and were submitted to chemical, physics, and microscopic analyses. The rocks were also submitted to total elements chemical analyses, X-Ray diffraction and scanning electronic microscopy. Six products of phosphatization were observed in ASPSP. Phosphates rocks were characterized by the accumulation and/or interaction of P- rich solutions with the substrate. Among them, it thick phosphates crusts occur on milonitizaded peridotites, phosphates espeleotems on the borders and inner fractures. Also we find phosphates filling out weathering fractures or constituting framboidals coats on their borders, as well as rich greenish phosphate crusts with Ni and Cr, guano and ornitogenic soils. The latter is represented by a Lithosol with high P content and fragmentary lithic character. In Rata Island, Noronha Arquipelago, we identified sloping Neosols, associates with calcarenites dissolution, whose physical and chemical properties indicate signs of pedogenetic evolution, and Cambisols in the rest of the island. These Cambisols are originated from calcarenites and basalts under low weathering degree. Phosphatization of these soils was processed in past conditions, under vanying humid to arid conditions. Colluviation processes mixed to phosphatizaded carbonatic san with a Al-P coating. Through this, it is observed a variscitization of P-Ca fragments, constituting P-Al oolitic aggregates. / A utilização das ilhas oceânicas por diversas espécies migratórias de aves faz com que estes animais depositem seus excrementos sobre seus substratos, fosfatizando-os. A fosfatização tem sua ocorrência relacionada a condições ambientais específicas e, por isso, é capaz de revelar evidências de mudanças ambientais pretéritas, associadas ao clima, correntes oceânicas, mudanças do nível do mar, entre outras. Além disso, exerce forte influência na ciclagem de nutrientes e na produtividade biológica das áreas marinhas adjacentes. Mesmo assim, pouco se conhece sobre este processo e como ele pode afetar a formação de solos insulares. Diante disso, este trabalho objetivou caracterizar a fosfatização nos Arquipélagos de São Pedro e São Paulo (ASPSP) e Fernando de Noronha (AFN), mais especificamente nas ilhas Belmonte e Rata, respectivamente. Foram coletadas amostras de rochas e solos fosfatizados nos dois arquipélagos. Os solos foram submetidos a análises químicas, físicas e microscópicas. As rochas, por sua vez, foram submetidas a análises químicas de elementos totais, Difração de Raio-X, microscopia eletrônica de varredura e microssondagens. No ASPSP foram observados seis produtos da fosfatização. As rochas fosfatizadas compreendem tipos ou feições que se caracterizam pela acumulação e/ou interação de soluções ricas em fósforo com o embasamento (rochas ultramáficas infracrustrais). Dentre tais feições, destacam-se crostas fosfáticas espessas sob peridotitos milonitizados, espeleotemas ou florescências de fosfatos nas bordas e interior de fraturas, formas de fosfatos percolados preenchendo fraturas intemperizadas ou constituindo revestimento framboidais em suas bordas, crostas esverdeadas ricas em P, Ni e Cr, guano e solos ornitogênicos, sendo o último um perfil de Neossolo Litólico com altos teores de P e caráter lítico fragmentário. Na Ilha Rata, AFN, são encontrados Neossolos nas baixadas, associados a um relevo ruiniforme proveniente da dissolução de calcarenitos, cujas propriedades físicas e químicas indicam sinais de sua evolução pedogenética, e Cambissolos no restante da Ilha. Os Cambissolos são originados de arenitos carbonáticos e de lavas ankaratríticas e se apresentam mais intemperizados. A fosfatização destes solos se processou em condições pretéritas, onde, numa fase mais árida, processos de coluvionamento misturaram à matriz carbonática, já fosfatizada, sedimentos aluminosos também fosfatizados. O que se observa, a partir disso, é a variscitação dos fragmentos de P-Ca constituindo agregados oolíticos de P-Al.

La thèse présentée porte sur les possibilités d’utilisation de la spectroscopie sur plasma induit par laser (LIBS) utilisée dans le laboratoire ainsi qu’à l’extérieur en utilisant l’appareil portable mis au point par nous et destiné pour analyser la composition élémentaire en matières. Cet appareil a été testé sur les échantillons géologiques dans l’objectif de la détection du Laacher See Tephra (LST) dans la craie lacustre enlevée dans le Jura en France. Le traitement statistique des cartes élémentaires pour les éléments Al, Ca, Fe, Ti, Ba et Na ont été effectuées à partir d’une coupe de la colonne sédimentaire contenant LST et cela a permis d’optimiser les conditions de l’expérience. La profilométrie a été utilisée sur les échantillons d’ammonites dans l’objectif de déterminer le processus de la fossilisation. La pyritisation a été considérée comme potentiellement détectable, mais l’appareil s’est révélé incapable de déterminer la phosphatation. Concernant le LIBS effectué dans le laboratoire, une réponse spectrale du spectromètre à échelle a été déterminée dans une gamme comprise entre 215 nm et 950 nm. Le modèle du rayonnement des molécules diatomiques de N2, NO et OH a été utilisé pour obtenir la source du rayonnement de référence de la décharge luminescente dans l’air. La réponse spectrale a été utilisée pour la correction des spectres mesurés dans d’autres recherches. Pour des tests sans calibration (CF-LIBS), les échantillons d’alliages d’aluminium avec de différentes compositions des éléments (Al, Mg, Mn, Si et Cu) ont été utilisés. Les résultats de l'acquisition des spectres de la localisation de 2 mm au-dessus de la surface de l’échantillon sont plus précis que ceux qui ont été acquis de la localisation de 1 mm. Une étude examinant des possibilités d’utilisation de l’auto-absorption pour analyser la concentration du magnésium dans les alliages d’aluminium est présentée dans le dernier chapitre de la thèse. A cette fin, un modèle bicouche de plasma a été utilisé et ajusté aux profiles des raies du Mg I 285,213 nm et Mg II 280,271 nm expérimentalement mesurés. Les résultats ont été comparés avec les valeurs nominales et pour la raie d’ion du Mg II 280,271 le résultat démontre une possibilité de déterminer la concentration du Mg dans l’alliage / No abstract

Laser Induced Breakdown Spectroscopy (LIBS) offers possibility for fast de- tection of sample composition without its preparation. For this reason it is attractive anywhere where the fast detection and no sample preparation are needed. As in many other branches the technical and scientific progress im- proves and spreads the possibilities of LIBS based devices and laboratory appa- ratuses. The time-resolved spectroscopy is allowed by spectrograph equipped with fast camera, broadband spectra can be acquired in single exposition by broadband spectrometers. Smaller and lighter laser sources together with com- pact spectrometers can be implemented to portable device and can be used out of laboratory. Computers offer quick data processing. The device named ChemCam installed on the NASA's next Mars rover, curiosity, is good exam- ple of high technology application in LIBS. However, there are still challenges and we hope that this work will be fruitful for anyone who is interested in the LIBS. The project of presented thesis was performed as a joint supervision project between the Department of Experimental Physics at Comenius University in Bratislava and Laboratiore Interdisciplinaire Carnot de Bourgogne at Univer- sit ́e de Bourgogne in Dijon. The aim of the project was to join experience from both laboratories, experience in laser constructions from Dijon and experience with spectroscopy from Bratislava. The both are essential for LIBS. In Bratislava the work was coordinated by prof.Pavel Veis and it was fo- cused on LIBS under the laboratory conditions. The time-resolved broadband spectrometry was used in the research. In order to achieve required spectra, the spectral response of the optical system was determined which was later used for the corrections. The research of self-absorption phenomena started in the last period with aim to use this effect, usually considered as negative, for the composition determination. In Dijon the work was supervised by Dr. Olivier Musset and directed toward development of LIBS device which could be used out of laboratory. The small 6 7 laser which was previously developed in the laboratory was implemented in the device. The development was successfully finished and testing process began in the last period of the thesis. The geological samples have been used for the testing process which was performed in deep cooperation with geologists. The first chapter comprises a brief introduction to LIBS. It is divided into some parts about laser induced plasma, laser induced breakdown and evolution of the plasma after breakdown. The section dealing with local thermodynamic equilibrium is also included. The section describes importance of LTE and the possibilities to determine this state. The second chapter is dedicated to the developed portable LIBS device. In the introduction, different type of LIBS devices are presented with their possibilities. Then the portable device developed in Dijon is described part by part with brief characteristic of developed software. The device possibilities and limits are sketched in the last section of the chapter with respect to results obtained in the testing process. The third chapter deals with capabilities of LIBS apparatus which was set up in the laboratory. The process of spectral response measurement and its results are presented and consequently used in next sections in process of plasma parameters determination. The composition of used samples are determined by using of calibration free method with aim to choose proper location in the plasma for which results are the most representative. The last chapter includes introduction to the subject of self-absorption phenomena. The simple model and basic theory are presented with suggestion how to use the phenomena in positive way. The simple experiment and its results are presented at the end of the chapter together with discussion about the possibilities and perspectives of the suggested method.