Weeks Bay, AL is a governmentally protected reserve near Mobile Bay, AL, while Old Tampa Bay, FL is an urbanized estuary, located along the western coast of Florida. Estuary health is important to local economies and the health of local marine life, with an emphasis on low levels of eutrophication. Sediment oxygen demand (SOD) is usually measured to qualify the environmental health of estuaries, but SOD is timeconsuming and expensive. Average acid volatile monosulfides (AVS) concentrations were found to accurately predict SOD variances. The Degree of Pyritization (DOP) is a measure of long-term sediment oxidation conditions, which indicates normal estuary state. Despite the urban land use practices of these two bays, the DOP of each bay is similar.

Methylmercury (MeHg) production is magnified in the natural environment by geochemical influxes and an active sulfate reducing bacteria community. It has been found that the presence of sulfides, excess nutrients, and the type of depositional environment (normal marine or euxinic) greatly influences MeHg production and degree of pyritization (DOP). The aim of this research is to investigate a possible connection between MeHg accumulation and the DOP in Weeks Bay sediment. Collected sediment samples have confirmed a significant presence of total reduced sulfides, inorganic mercury, reactive iron, and total organic carbon. Pyritization results indicate a normal marine environment and, of the three measured elements (S, Fe, and C,) carbon and sulfur are the dominant limiting factors to the DOP in Weeks Bay. Current geochemical and pH/redox conditions favor MeHg and pyrite production. The quantified pyrite greatly exceeds that of MeHg indicating DOP inhibits MeHg precipitation.

No description available.

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

No description available.

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.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2018-03-12T17:39:30Z No. of bitstreams: 1 Tese Manuel Moreira.pdf: 26683391 bytes, checksum: 22f4cca548ed444677c5428a580b351d (MD5) / Made available in DSpace on 2018-03-12T17:39:30Z (GMT). No. of bitstreams: 1 Tese Manuel Moreira.pdf: 26683391 bytes, checksum: 22f4cca548ed444677c5428a580b351d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / A acumulação dos elementos-traço nos sedimentos desempenha um importante papel na ciclagem destes elementos nos ambientes marinhos, associado a variáveis formas de retenção no reservatório sedimentar, em diferentes escalas temporais. No presente estudo foi avaliado o fracionamento geoquímico de Fe, Mn, As, Cd, Co, Cr, Cu, Mo, Ni, Pb e Zn entre as frações solúveis em HCl, associada à pirita (FeS2) e associada à fração orgânica, como forma de elucidar os processos que determinam a acumulação destes elementos nos sedimentos da plataforma continental do Sistema de Ressurgência de Cabo Frio (SRCF) nos últimos 8.000 anos. Foi observado que o fracionamento dos elementos Fe, Mn, As, Cr, Ni, Pb e Zn apresenta uma maior proporção na fração solúvel em HCl nos três testemunhos sedimentares coletados ao longo da plataforma continental. O Cu em todas as estações apresentou uma maior proporção na fração da matéria orgânica. O Cd (plataforma interna) e o Pb (plataforma externa) apresentaram uma fração da matéria orgânica importante. O Mo apresentou uma fração pirítica mais importante. O fracionamento geoquímico demonstrou que as formas nas quais os elementos foram acumulados, indicam fortemente influência da diagênese sedimentar. As concentrações de Fe e de S pirítico não foram fatores limitantes no grau de piritização dos elementos-traço. A associação de elementos-traço, tanto à fração ligada à MO quanto à fração ligada à pirita, contribuiu para determinar a retenção de elementos nos sedimentos. Quanto mais intensos foram os processos de re-oxidação do ciclo do S (indicados pela assinatura isotópica da pirita, δ34S), maior foi o grau de piritização do Pb, ao contrário do encontrado para Fe, Cu e Mo, em áreas específicas da plataforma. A estabilização do nível do mar foi o principal evento paleo-oceanográfico determinando a variação vertical da acumulação nos últimos 8.000 anos cal AP, sendo que a variabilidade dos fluxos dos elementos estudados (em relação ao somatório das frações não-detríticas obtidas na extração sequencial) não tendeu a acompanhar a variabilidade do fracionamento geoquímico. Mesmo sob condições oxidantes da coluna d’água, pode ser encontrado um sinergismo da associação à MO e à pirita, contribuindo para determinar a retenção de elementos como Cd, Co, Cu, Mo e Pb nos sedimentos / The accumulation of trace elements in the sediments plays an important role in the cycling of these elements in marine environments, associated with different forms of retention in the sedimentary reservoir, at different time scales. In the present study, the geochemical fractionation of Fe, Mn, As, Cd, Co, Cr, Cu, Mo, Ni, Pb and Zn was evaluated between the fractions soluble in HCl, associated with pyrite (FeS2) and associated with the organic fraction, To elucidate the processes that determine the accumulation of these elements in sediments of the continental shelf of the Cabo Frio Upwelling System (CFUS) in the last 8,000 years. It was observed that the fractionation of the elements Fe, Mn, As, Cr, Ni, Pb and Zn presents a higher proportion in the soluble fraction in HCl in the three sediment cores collected along the continental shelf. Cu in all seasons presented a higher proportion in the fraction of organic matter. The Cd (inner shelf) and the Pb (outer shelf) presented a fraction of the important organic matter. Mo presented a more important pyritic fraction. Geochemical fractionation has shown that the forms in which the elements are being accumulated are strongly influenced by sedimentary diagenesis. The concentrations of Fe and S pyritic were not limiting factors in the degree of piritization of trace elements. The association of trace elements to the fraction bound to the MO and to the fraction bound to pyrite contributed to determine the retention of elements in the sediments. The more intense the S-cycle re-oxidation processes (indicated by the isotopic signature of pyrite, δ34S), the higher the Pb pyritization degree, as opposed to Fe, Cu and Mo, in specific areas of the shelf. The stabilization of the sea level was the main paleo-oceanographic event determining the vertical variation of the accumulation in the last 8,000 years BP. The variability of the fluxes of the elements studied (in relation to the sum of the non-detrital fractions obtained in the sequential extraction) did not tend to follow the variability of the geochemical fractionation. Even under oxidizing conditions of the water column, a synergism of the association with OM and pyrite can be found, contributing to determine the retention of elements such as Cd, Co, Cu, Mo and Pb in the sediments

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2016-04-13T15:18:33Z No. of bitstreams: 1 Mestrado Manuel Moreira.pdf: 7413069 bytes, checksum: 0f15055b235c438ffd4fac6dde85f099 (MD5) / Made available in DSpace on 2016-04-13T15:18:33Z (GMT). No. of bitstreams: 1 Mestrado Manuel Moreira.pdf: 7413069 bytes, checksum: 0f15055b235c438ffd4fac6dde85f099 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ / Elementos-tarços são freqüentemente utilizados como indicadores das condições redox e da paleoprodutividade marinha, que podem afetar a distribuição e o fracionamento geoquímico destes elementos. O potencial efeito do ciclo re-oxidativo da pirita sedimentar sobre o grau de piritização destes indicadores (degree of trace metal pyritization – DTMP) não tem sido anteriormente avaliado. Esta avaliação foi realizada em testemunhos sedimentares da plataforma continental sob influência do Sistema de Ressurgência de Cabo Frio (RJ). A relação do DTMP com a assinatura isotópica do S na pirita (δ34S), que se torna mais leve em resposta ao ciclo re-oxidativo da pirita na área de estudo, sugere que a influência pode ser alta (para Pb, As, Cd e Mn), baixa (para Zn e Cu) ou desprezível (para Cr e Ni), dependendo do elemento considerado. Sedimentos mais antigos e ricos em pirita possibilitaram a identificação de um aparente limiar para o efeito da re-oxidação, após o qual os elementos Pb, As, Cd, Mn e Zn apresentaram maior piritização. Um testemunho em posição intermediária na plataforma apresentou correlações negativas das concentrações reativas de Mn, Cu, Ni e Pb com as concentrações de Fe na pirita, assim como outros dois testemunhos apresentaram em relação a Mn e Pb. Isto sugere um consumo de óxidos de Mn (e metais associados) em reação com a pirita, contribuindo para explicar o alto DTMP apresentado pelo Pb, que discorda das predições termodinâmicas e de cinética de incorporação deste metal pela pirita. As assinaturas isotópicas da pirita na área de estudo (que apresenta condições óxicas), foram semelhantes às de ambientes sedimentares anóxicos e euxínicos reportadas na literatura, sugerindo que o ciclo re-oxidativo pode afetar a susceptibilidade de incorporação e a preservação dos elementos na pirita em uma ampla variedade de condições sedimentares. A abordagem metodológica proposta pode subsidiar a melhor interpretação do processo de piritização e suas aplicações para a indicação de condições paleo-redox e de paleo-produtividade / Potential effects of sedimentary pyrite re-oxidative cycling on the degree of trace metals pyritization (DTMP) were evaluated in four sediment cores from the continental shelf under the influence of a tropical upwelling system (Cabo Frio, Brazil). The DTMP relation with stable isotope signals (δ34S) of chromium reducible sulfur, which became lighter in response to intense pyrite re-oxidative cycling in the study area, suggests high (Pb, As, Cd and Mn), low (Zn and Cu) or negligible (Cr and Ni) re-oxidation influences. Oldest pyrite-richer sediments provide an apparent threshold for intense pyrite re-oxidation, after which most trace elements (Pb, As, Cd, Mn and Zn) presented more accentuated DTMP. A middle shelf core presented negative correlations of reactive Mn, Cu, Ni and Pb with pyrite iron, suggesting Mn oxide (and associated metals) depletion in reaction with pyrite. This contributes to explain the observed high degree of Pb pyritization in disagreement with predictions derived from both thermodynamics and water exchange reaction kinetics. Pyrite δ34S signatures under the oxic bottom water from the study area were similar to those from euxinic sedimentary environments, suggesting that pyrite re-oxidative cycling can affect trace element susceptibility to be incorporated and preserved into pyrite in a wide range of sedimentary conditions