Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2016-09-28T13:47:04Z No. of bitstreams: 1 2011- Marcio Osvaldo Lima Magalhaes.pdf: 4632406 bytes, checksum: 8ccefc16f724417fcb426aaf9aac9f4a (MD5) / Made available in DSpace on 2016-09-28T13:47:04Z (GMT). No. of bitstreams: 1 2011- Marcio Osvaldo Lima Magalhaes.pdf: 4632406 bytes, checksum: 8ccefc16f724417fcb426aaf9aac9f4a (MD5) Previous issue date: 2011-12-19 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Despite the known problems caused by the by-products generated from the exploration of oil, this activity will be a part of our reality for the next 50 years. The oil drilling and exploration industry creates a substantial amount of waste that, if not adequately disposed of, could cause environmental problems. One of the main contaminates found in the waste related to oil drilling is the element barium. The purpose of this study was to evaluate the contamination of soil containing barium, its impact on the growth of rice plants (Orysa sativa) and potential risk of contaminating groundwater. This paper was divided into four chapters. The goal of the first chapter was to evaluate the spatial variability of barium levels found in former oil well drilling waste disposal sites. For this study, soil was collected from georeferenced points, analyzed in terms of its pseudo total levels, and prepared for the geochemical fractionation of barium, classifying the material in accordance with resolution 420 of CONAMA [Brazilian National Counsel on the Environment] (2009). In the second chapter, the effect of redox potential in soil on the mobility and absorption of barium by rice, having barium sulfate P.A. as the element?s source, was assessed. The effect was evaluated by performing rice culture pot and column leaching tests. The aim of the third chapter was the characterization and traceability of heavy metals in waste generated during the recovery of oil well drilling fluids. The waste was collected during the drilling of well 7-MGP-98D-BA, where the material was separated by composite sample, based on depth and equipment. In the fourth chapter, the effects of redox potential in soil interaction and heavy metals coming from the waste generated from onshore oil well drilling were analyzed. This chapter was similar to chapter two, with the main difference being the waste generated from well 7-MGP-98D-BA, which supplied the source of barium. The waste materials selected were those that displayed the lowest levels of arsenic, cadmium, barium, lead, and sodium. The obtained results showed that waste generated from oil well drilling contains high levels of barium, and that when disposed of in soil can significantly contribute to site contamination, having used the guiding values of CONAMA (2009) as a reference. As such, the barium present in this area was in the form of low solubility, as evidenced by the geochemical fractionation of the element. It was also observed that the conditions of low values of redox potential (-200 mV) promoted an increase of barium in fractions of greater mobility, causing major losses of the element by leaching, and increased absorption by plants. Among the studied waste materials, the waste from the dehydrator and the centrifuge 1 presented high levels of sodium as its greatest limitation, which affected the development of plants. / Apesar da verifica??o de problemas ocasionados pelo uso de produtos gerados a partir da explora??o do petr?leo, essa atividade ? uma realidade nos pr?ximos 50 anos. A industria de perfura??o e explora??o de petr?leo ? uma atividade que gera muitos residuos que, caso dispostos de forma inadequada, podem ocasionar problemas ambientais. Um dos principais contaminantes relacionados aos res?duos de perfura??o de po?os de petr?leo ? o elemento b?rio. A proposta desse estudo foi de avaliar a contamina??o dos solos com b?rio e seu impacto no desenvolvimento de plantas de arroz (Orysa sativa) e o risco de contamina??o do len?ol fre?tico. Para isso o trabalho foi dividido em quatro cap?tulos. O primeiro cap?tulo teve como objetivo avaliar a variabilidade espacial dos teores de b?rio em antiga ?rea de disposi??o de res?duo de perfura??o de po?os de petr?leo. Nesse estudo foram coletados solos em pontos georreferenciados e analisados quanto aos teores pseudototais e feito o fracionamento geoqu?mico do b?rio, classificando o material de acordo com a resolu??o 420 do Conama (2009). No segunto cap?tulo foi avaliado o efeito do potencial redox do solo na mobilidade e absor??o de b?rio por arroz, tendo como fonte do elelmento o sulfato de b?rio P.A. Esse efeito foi avaliado atrav?s de ensaios em vasos com cultivo de arroz e em colunas de lixivia??o. O terceiro cap?tulo teve como objetivo a caracteriza??o e rastreabilidade de metais pesados em res?duos gerados na recupera??o do fluido de perfura??o de po?os de petr?leo. O res?duo foi coletado durante a perfura??o do po?o 7-MGP-98D-BA, onde os materiais foram separados em amostras compostas em fun??o da profundidade e do equipamento. No quarto cap?tulo foi analisado o efeito do potencial redox na intera??o solo e metais pesados provenientes de res?duos oriundos da perfura??o de po?os de petr?leo ?onshore?. Esse cap?tulo foi semelhante ao cap?tulo 2, diferindo principalmente na fonte de b?rio que foi o res?duo gerado no po?o 7-MGP-98D-BA. Os res?duos selecionados foram os que apresentaram como os mais restrit?vos com rela??o aos teores de ars?nio, c?dmio, b?rio, chumbo e s?dio. Os resultados obtidos evidenciaram que os res?duos oriundos da perfura??o de po?os de petr?leo possuem altos teores de b?rio, que quando dispostos nos solos podem contribuir significativamente para a contamina??o das ?reas, tendo como refer?ncia os valores orientadores do Conama (2009). Entretanto, o b?rio presente nessa ?rea estava sob forma de baixa solubilidade, evidenciada pelo fracionamento geoqu?mico do elemento. Tamb?m foi observado que a condi??o de baixos valores de potencial redox (-200 mV) promoveu o aumento do b?rio nas fra??es de maior mobilidade, ocasionando maiores perdas do elemento por lixivia??o e maior absor??o pelas plantas. Dentre os res?duos estudados, os res?duos do secador e da centr?fuga 1 apresentaram como maior limita??o os altos teores de s?dio, o que afetou o desenvolvimento das plantas.

CNPq / Faced with the need to implement a sustainable development, and seeking solutions for protecting the environment, the management of residues has undergone marked changes. Companies are increasingly involved in the optimization of residues produced in their production processes. The oil industry participates in this search by funding research and development of environmentally sound technologies. This study aimed to evaluate the development of barley plants (Hordeum vulgare L.) in soils incubated with drill waste from oil well treated by washing to eliminate the influence of sodium. Two residues generated during drilling of the well 7-SMC-50D-AL were selected to be used in two assays: one in pots planted with barley, and one with leaching columns. For the pots testing the residues were washed with water, using a ratio of 1:5, aiming to reduce the effects of the sodium. Thus, the washing treatment defined two other conditions: residue washed and unwashed. The quantity of residue added to the soil was defined in order to obtain the barium concentrations of 300 mg kg-1, 600 mg kg-1 and 1200 mg kg-1. The soil moisture was maintained at 70% of field capacity. The experimental units were kept incubated for 30 days, and covered with plastic bags to prevent water loss by evaporation. The plants sowing was made using 10 seeds in each pot, and after the thinning with 30 days there was left 4 plants per pot. After the harvesting, the plants were separated into root, shoot and grain; and it was evaluated the absorption of the elements barium, iron, manganese, calcium, sodium, zinc and potassium. The results showed that the residues of the centrifugal and the dryer promoted an increased production of plant dry matter, especially in the treatment with the residue washing. For the test columns, there was no washing of the residues. The same doses were tested with two conditions of humidity (70% of field capacity and reduced condition, simulating the presence of a ground water table). During the incubation the pH and the redox potential (Eh) were monitored until, in the reduction condition, values close to ? 200 mV were obtained, and then, waiting for 30 days to ensure the occurrence of the reduction reactions. After that, the leaching test proceeded, simulating rainfall and collecting the extract leachate to evaluate the barium content. The geochemical fractionation of barium was done using a modification of the BCR method. The fractionation results showed that the reduction condition provided greater availability of barium, increasing the bioavailable fraction for both cuttings. In the leaching test, there was an increase in barium level in the reduction condition, due to the reduction of sulfate to sulfide. / Diante da necessidade de implementar o desenvolvimento sustent?vel, buscando solu??es para a prote??o do meio ambiente, a gest?o de res?duos tem passado por mudan?as marcantes. As empresas est?o cada vez mais envolvidas na otimiza??o de res?duos produzidos em seus processos produtivos. A ind?stria petrol?fera participa dessa busca por solu??es atrav?s do financiamento de pesquisas e do desenvolvimento de tecnologias ambientalmente seguras. Este trabalho teve como objetivo avaliar o desenvolvimento de plantas de cevada (Hordeum vulgare L.) em solos incubados com res?duos de perfura??o de po?o de petr?leo tratados com lavagem para eliminar a influ?ncia do s?dio. Foram selecionados dois res?duos gerados durante a perfura??o do Po?o7-SMC-50D-AL para serem utilizados em dois ensaios: um com vasos cultivados com cevada e outro com colunas de lixivia??o. Para o ensaio com vasos foi feita a lavagem dos res?duos em ?gua, na propor??o 1:5, visando diminuir os efeitos do s?dio. Dessa forma, o tratamento de lavagem definiu duas condi??es: res?duo lavado e res?duo n?o lavado. A quantidade de res?duo adicionada ao solo foi definida de modo a atingir as concentra??es de b?rio de 300 mg kg-1, 600 mg kg-1 e 1200 mg kg-1. A umidade do solo foi mantida a 70% da capacidade de campo. As unidades experimentais permaneceram incubadas por 30 dias, cobertas com sacos pl?sticos para evitar a perda de ?gua por evapora??o. Em seguida foi feita a semeadura, utilizando 10 sementes em cada vaso, e com o desbaste ap?s 30 dias restaram apenas 4 plantas por vaso. Ap?s a coleta as plantas foram separadas em raiz, parte a?rea e gr?os e foi avaliada a absor??o dos elementos b?rio, ferro, mangan?s, c?lcio, s?dio, zinco e pot?ssio. Os resultados obtidos demonstraram que os res?duos do secador e da centr?fuga promoveram aumento da produ??o de mat?ria seca pelas plantas, principalmente no tratamento lavado. Para o ensaio com colunas n?o houve lavagem dos res?duos. Foram testadas as mesmas doses em duas condi??es de umidade (70% da capacidade de campo e ambiente reduzido com presen?a de l?mina de ?gua). Durante a incuba??o foi feito o monitoramento de pH e potencial redox (Eh) at? que, na condi??o de redu??o, fossem atingidos valores pr?ximos de -200 mV, aguardando por 30 dias para assegurar a ocorr?ncia das rea??es de redu??o. Em seguida foi feito o ensaio de lixivia??o, simulando uma precipita??o e coletando o extrato lixiviado para avalia??o quanto ao teor de b?rio. Foi feito o fracionamento geoqu?mico do elemento b?rio utilizando-se o m?todo BCR com algumas modifica??es. Os resultados mostraram que no fracionamento as fra??es biodispon?vel para ambos os res?duos na condi??o de redu??o proporcionou uma maior disponibilidade do b?rio. Na lixivia??o houve um aumento dos teores de b?rio na condi??o de redu??o proporcionado pela redu??o de sulfato a sulfeto.

The Ni-Fe-S C-cluster of carbon monoxide dehydrogenases (CODH), which catalyzes the reversible oxidation of CO to CO2, can be stabilized in four redox states: Cox, Cred1, Cint, and Cred2. The best-supported mechanism of catalysis involves a one-electron reductive activation of Cox to Cred1 and a catalytic cycle in which Cred1 binds and oxidizes CO, forming Cred2 and releasing CO2. Recently reported experiments appear to have disqualified this mechanism, as activation was concluded to require reduction to a C-cluster state more reduced than Cred1. The results presented in this dissertation suggest that the activation potential was milder than that required to reduce these clusters. The results support a mechanism in which Cred1 is the form of the cluster that reacts with CO. The structure of the active-site C-cluster in CO dehydrogenase from Carboxydothermus hydrogenoformans (CODHCh) includes a ??2-sulfide ion bridged to the Ni and unique Fe, while the same cluster in enzymes from Rhodospirillum rubrum (CODHRr) and Moorella thermoacetica (CODHMt) lack this ion. This difference was investigated by exploring effects of sulfide on activity and spectral properties. Sulfide partially inhibited CO oxidation activities of CODHRr and CODHMt. Adding sulfide to CODHMt in the Cred1 state caused the gav = 1.82 Electron Paramagnetic Resonance spectroscopy (EPR) signal to decline and new features to appear. Sulfide did not affect the gav = 1.86 signal from the Cred2 state. A model was developed in which sulfide binds reversibly to Cred1, inhibiting catalysis. The results also suggest that the substrate hydroxyl group bridges the Ni and unique Fe. A cysteine residue recently found to form a persulfide bond with the C-cluster was characterized. The Ser mutant of the persulfide-forming Cys316 was inactive and displayed no C-cluster EPR signals. Electronic absorption and metal analysis suggest that the C-cluster is absent in this mutant. The persulfide bond appears to be essential for either the assembly or stability of the C-cluster, and/or for eliciting the redox chemistry of the C-cluster required for catalytic activity.

The Ni-Fe-S C-cluster of carbon monoxide dehydrogenases (CODH), which catalyzes the reversible oxidation of CO to CO2, can be stabilized in four redox states: Cox, Cred1, Cint, and Cred2. The best-supported mechanism of catalysis involves a one-electron reductive activation of Cox to Cred1 and a catalytic cycle in which Cred1 binds and oxidizes CO, forming Cred2 and releasing CO2. Recently reported experiments appear to have disqualified this mechanism, as activation was concluded to require reduction to a C-cluster state more reduced than Cred1. The results presented in this dissertation suggest that the activation potential was milder than that required to reduce these clusters. The results support a mechanism in which Cred1 is the form of the cluster that reacts with CO. The structure of the active-site C-cluster in CO dehydrogenase from Carboxydothermus hydrogenoformans (CODHCh) includes a ??2-sulfide ion bridged to the Ni and unique Fe, while the same cluster in enzymes from Rhodospirillum rubrum (CODHRr) and Moorella thermoacetica (CODHMt) lack this ion. This difference was investigated by exploring effects of sulfide on activity and spectral properties. Sulfide partially inhibited CO oxidation activities of CODHRr and CODHMt. Adding sulfide to CODHMt in the Cred1 state caused the gav = 1.82 Electron Paramagnetic Resonance spectroscopy (EPR) signal to decline and new features to appear. Sulfide did not affect the gav = 1.86 signal from the Cred2 state. A model was developed in which sulfide binds reversibly to Cred1, inhibiting catalysis. The results also suggest that the substrate hydroxyl group bridges the Ni and unique Fe. A cysteine residue recently found to form a persulfide bond with the C-cluster was characterized. The Ser mutant of the persulfide-forming Cys316 was inactive and displayed no C-cluster EPR signals. Electronic absorption and metal analysis suggest that the C-cluster is absent in this mutant. The persulfide bond appears to be essential for either the assembly or stability of the C-cluster, and/or for eliciting the redox chemistry of the C-cluster required for catalytic activity.

Hexachloro-1,3-butadiene (HCBD) is a toxic aliphatic chlorinated hydrocarbon which is widely used as a fungicide, herbicide and heat transformer fluid. HCBD is resistant to microbial degradation and, therefore, persists in aquatic and soil environments worldwide. In this thesis, the ability of non-specific bacteria from various sources to dechlorinate HCBD in the presence of either acetate or lactate (as an electron donor) and cyanocobalamin (as an electron shuttle) under different conditions was investigated. Cultivating specific populations to reduce cyanocobalamin as a method to increase HCBD dechlorination rate was investigated. Also, the factors responsible for HCBD dechlorination and the stalling of dechlorination were studied. Lastly, redox potential measurement during the microbial reductive dechlorination of HCBD for online detection of ongoing dechlorination was evaluated. Findings from the Project „« Non-specific bacteria from activated sludge, anaerobic digested effluent from municipal waste, piggery waste and sheep rumen content are able to dechlorinate HCBD in the presence of cyanocobalamin to chlorine-free C4 gases in a biochemical reaction. „« Dechlorination was equated to the formation of completely dechlorinated end-products from HCBD dechlorination. „« Methanogens were found to be involved in HCBD dechlorination. „« Mediators rather than specific bacteria were responsible for the fast dechlorination rates. Results suggest that activated sludge may release synthesized mediators into the supernatant to enable enhanced HCBD dechlorination. „« HCBD dechlorination can be monitored using oxidation reduction potential (ORP). ORP has an effect on HCBD dechlorination rate. Scientific Significance/Novelty The most significant finding from this research is that it demonstrates chlorine-free end-products in contrast with other studies in literature (Booker and Pavlosthasis, 2000; Bosma et al., 1994) where dechlorination was equated with disappearance of HCBD into bacterial biomass and the detection of partially dechlorinated gases such as trichlorobutadiene. It also shows that, in contrast to literature where specific bacteria (i.e., pure strains/cultures) were commonly used for the dechlorination of polychlorinated hydrocarbons, results from this thesis show that non-specific bacteria were able to dechlorinate HCBD in the presence of cyanocobalamin at ratesƒx sufficiently high to be considered for bioremediation projects. Moreover, results demonstrate that ORP can be used to monitor HCBD dechlorination.

Diss. (sammanfattning) Stockholm : Tekn. högsk. / Härtill 4 uppsatser.

Fatty acid components on yeast plasma membrane were critical in maintaining proper cell activity during bioethanol fermentation. The alteration of fatty acid composition on yeast plasma membrane was recognized as an adaptive response to several environmental stress including osmotic pressure, ethanol inhibition and nutrients limit. These stresses were exacerbated under very-high-gravity condition in which excessive fermentable sugar was provided in feedstock. Controlling redox potential was proved beneficial in improving yeast performance under very-high-gravity condition. Fatty acid synthesis and desaturation pathways involved dissolved oxygen as well as balance between NAD+/NADH and NADP+/NADPH which could be influenced by the regulation of redox potential in media. In this study, fatty acid composition profiles under different glucose concentrations and different redox potential control level were examined. Its connection with yeast cell growth, ethanol productivity and other metabolites’ concentrations were studied as well to reveal any causal correlation between redox potential control, membrane fatty acid composition and yeast activity. Two glucose concentrations used in this study were 200 g/L and 300 g/L which represented normal and very high gravity respectively in bioethanol fermentation. In 300 g/L fermentation, three redox conditions were adopted while two different redox conditions were used in 200 g/L fermentation. Biomass concentration, ethanol productivity and fatty acid composition were observed to be affected by both gravity and ORP control strategy. Final biomass concentrations were 4.302 g/L in 200 g/L glucose with no ORP control condition and 7.658 in 200 g/L glucose with ORP controlled at -100 mV condition. In 300 g/L glucose fermentation, final biomass concentrations were 3.400 g/L for no ORP control, 4.953 g/L for -150 mV ORP control and 5.260 for -100 mV ORP control. Ethanol productivities were 2.574 g/Lh for 200 g/L glucose without ORP control and 3.780 g/Lh for 200 g/L glucose with -100 mV ORP control. In 300 g/L glucose fermentation, ethanol productivity decreased to 1.584 g/Lh when no ORP control was imposed. ORP control at -150 mV could improve the ethanol productivity to 1.693 g/Lh while -100 mV ORP control was able to further enhance the ethanol productivity to 1.829 g/Lh. Fatty acid composition was observed to shift to more saturated components when no ORP control was applied. Such trend of saturation was increased by higher gravity condition. ORP control was shown to change this tendency to saturation and help restore fatty acid components on plasma membrane to a more balanced distribution.

Os sedimentos aquáticos podem fornecer importantes subsídios na avaliação dos ecossistemas aquáticos lênticos, uma vez que grande parte dos nutrientes se encontra no estado sólido. A ocorrência de uma floração de cianobactérias tóxicas originada no Blang, segundo de três reservatórios em cascata do Sistema Salto de Hidrelétricas, localizado no município de São Francisco de Paula (RS), motivou a investigação das possíveis fontes de nutrientes, especialmente de fósforo (P) que foi identificado como limitante para a eutrofização. Foram investigadas fontes de origens difusas (solos, águas e sedimentos dos tributários) e pontuais (uso urbano e a carga interna representada pelo sedimento do leito dos reservatórios). Os resultados mostraram características oligotróficas nas fontes externas e a presença de P disponível em excesso no sedimento do leito, indicando que a carga interna poderia ser uma fonte significativa de nutrientes. A possibilidade de circulação da água hipolimnética foi investigada através de números adimensionais e características físicas do corpo de água, demonstrando que dificilmente ocorreria, uma vez que somente eventos climáticos extremos poderiam provocar a inversão da massa líquida. Excluídas as fontes externas, os resultados sugerem que a fertilização do reservatório Blang tenha sido causada pela abertura da comporta de fundo do reservatório Divisa, localizado imediatamente à montante, durante uma estiagem. O segundo objetivo desta pesquisa foi avaliar a importância dos agregados de partículas e da seleção granulométrica para a análise química de nutrientes em sedimentos aquáticos. Resultados obtidos em sedimentos de ambientes lóticos e lênticos (Sistema Salto, RS), demonstraram que os agregados maiores (465 - 63 μm) concentram nitrogênio nos ambientes lênticos, por isso a análise deve ser realizada, preferencialmente, na fração ≤ 465 μm em sedimentos de ambientes lênticos e na fração ≤ 63 μm dos ambientes lóticos. O último objetivo deste estudo foi testar os efeitos da oxidação sobre a capacidade e a velocidade da sorção de fosfato em sedimentos aquáticos orgânicos, identificando as melhores condições para retenção. Foram utilizados sedimentos aquáticos siliciclásticos de origens distintas, principalmente no que se refere ao clima e à origem do conteúdo orgânico, alóctone e autóctone, representados pelos tipos Dy (Reservatório Divisa, RS) e Sapropel (Reservatório de Tapacurá, São Lourenço da Mata, PE) respectivamente. O experimento foi realizado em suspensões de sedimentos mantidos sob níveis de potencial redox compreendidos entre - 200 mV e + 400 mV. Resultados demonstram que a sorção de fosfato é maior no sedimento tipo Dy em condições reduzidas e no Sapropel em condições oxidadas. / Water-borne sediments can provide important information for evaluating lentic aquatic ecosystems because a large proportion of their nutrients are found in the solid phase. A toxic algal bloom in the Blang Reservoir, the second of three in the Salto System chain of hydroelectric dams located in Sao Francisco de Paula in Rio Grande do Sul, Brazil, motivated the investigation of possible nutrient sources, especially phosphorus, which was identified as the limiting nutrient for eutrophization. Non-point sources, including soil, water and sediment carried by tributaries, and point sources, including urban areas and the internal load from the reservoir bottom, were examined. Results showed oligotrophic characteristics in the external sources and excess P availability in bottom sediments, indicating that the internal load may be a significant source of nutrients. The possible circulation of hypolimnic water was investigated using adimensional numbers and physical characteristics of the body of water, demonstrating that this is unlikely to occur, since only extreme climatic events could cause inversion of the liquid mass. By excluding external sources, results suggest that the fertilization of the Blang Reservoir was most likely caused by the opening of the floodgates from the Divisa Reservoir immediately upstream during a drought period. The second goal of this study was to evaluate the importance of particle aggregates and particle size selection for chemical analyses of nutrients and water-borne sediments. Results from sediments in lentic and lotic environments from the Salto System show that the larger aggregates (465 - 63 μm) concentrate nitrogen under lentic conditions and that, therefore, analyses should be performed on the fraction smaller than 465 μm in lentic environments and in the fraction ≤ 63 μm in lotic environments. The final objective of this study was to test the effects of oxidation on the phosphate sorption capacity and rate in organic aquatic sediments, identifying the best conditions for retention. Silicate aquatic sediments from different origins in terms of climate and source of organic content (allochtonous or autochtonous) were used, and were represented by the types Dy (Divisa Reservoir, RS) and Sapropel (Tapacurá Reservoir, São Lourenço da Mata, PE), respectively. The experiment was carried out in suspended sediment maintained under levels of redox potential between –200mV and +400mV. Results demonstrated that phosphate sorption is greatest in sediment type Dy under reduced conditions and in Sapropel under oxidized conditions.

Os sedimentos aquáticos podem fornecer importantes subsídios na avaliação dos ecossistemas aquáticos lênticos, uma vez que grande parte dos nutrientes se encontra no estado sólido. A ocorrência de uma floração de cianobactérias tóxicas originada no Blang, segundo de três reservatórios em cascata do Sistema Salto de Hidrelétricas, localizado no município de São Francisco de Paula (RS), motivou a investigação das possíveis fontes de nutrientes, especialmente de fósforo (P) que foi identificado como limitante para a eutrofização. Foram investigadas fontes de origens difusas (solos, águas e sedimentos dos tributários) e pontuais (uso urbano e a carga interna representada pelo sedimento do leito dos reservatórios). Os resultados mostraram características oligotróficas nas fontes externas e a presença de P disponível em excesso no sedimento do leito, indicando que a carga interna poderia ser uma fonte significativa de nutrientes. A possibilidade de circulação da água hipolimnética foi investigada através de números adimensionais e características físicas do corpo de água, demonstrando que dificilmente ocorreria, uma vez que somente eventos climáticos extremos poderiam provocar a inversão da massa líquida. Excluídas as fontes externas, os resultados sugerem que a fertilização do reservatório Blang tenha sido causada pela abertura da comporta de fundo do reservatório Divisa, localizado imediatamente à montante, durante uma estiagem. O segundo objetivo desta pesquisa foi avaliar a importância dos agregados de partículas e da seleção granulométrica para a análise química de nutrientes em sedimentos aquáticos. Resultados obtidos em sedimentos de ambientes lóticos e lênticos (Sistema Salto, RS), demonstraram que os agregados maiores (465 - 63 μm) concentram nitrogênio nos ambientes lênticos, por isso a análise deve ser realizada, preferencialmente, na fração ≤ 465 μm em sedimentos de ambientes lênticos e na fração ≤ 63 μm dos ambientes lóticos. O último objetivo deste estudo foi testar os efeitos da oxidação sobre a capacidade e a velocidade da sorção de fosfato em sedimentos aquáticos orgânicos, identificando as melhores condições para retenção. Foram utilizados sedimentos aquáticos siliciclásticos de origens distintas, principalmente no que se refere ao clima e à origem do conteúdo orgânico, alóctone e autóctone, representados pelos tipos Dy (Reservatório Divisa, RS) e Sapropel (Reservatório de Tapacurá, São Lourenço da Mata, PE) respectivamente. O experimento foi realizado em suspensões de sedimentos mantidos sob níveis de potencial redox compreendidos entre - 200 mV e + 400 mV. Resultados demonstram que a sorção de fosfato é maior no sedimento tipo Dy em condições reduzidas e no Sapropel em condições oxidadas. / Water-borne sediments can provide important information for evaluating lentic aquatic ecosystems because a large proportion of their nutrients are found in the solid phase. A toxic algal bloom in the Blang Reservoir, the second of three in the Salto System chain of hydroelectric dams located in Sao Francisco de Paula in Rio Grande do Sul, Brazil, motivated the investigation of possible nutrient sources, especially phosphorus, which was identified as the limiting nutrient for eutrophization. Non-point sources, including soil, water and sediment carried by tributaries, and point sources, including urban areas and the internal load from the reservoir bottom, were examined. Results showed oligotrophic characteristics in the external sources and excess P availability in bottom sediments, indicating that the internal load may be a significant source of nutrients. The possible circulation of hypolimnic water was investigated using adimensional numbers and physical characteristics of the body of water, demonstrating that this is unlikely to occur, since only extreme climatic events could cause inversion of the liquid mass. By excluding external sources, results suggest that the fertilization of the Blang Reservoir was most likely caused by the opening of the floodgates from the Divisa Reservoir immediately upstream during a drought period. The second goal of this study was to evaluate the importance of particle aggregates and particle size selection for chemical analyses of nutrients and water-borne sediments. Results from sediments in lentic and lotic environments from the Salto System show that the larger aggregates (465 - 63 μm) concentrate nitrogen under lentic conditions and that, therefore, analyses should be performed on the fraction smaller than 465 μm in lentic environments and in the fraction ≤ 63 μm in lotic environments. The final objective of this study was to test the effects of oxidation on the phosphate sorption capacity and rate in organic aquatic sediments, identifying the best conditions for retention. Silicate aquatic sediments from different origins in terms of climate and source of organic content (allochtonous or autochtonous) were used, and were represented by the types Dy (Divisa Reservoir, RS) and Sapropel (Tapacurá Reservoir, São Lourenço da Mata, PE), respectively. The experiment was carried out in suspended sediment maintained under levels of redox potential between –200mV and +400mV. Results demonstrated that phosphate sorption is greatest in sediment type Dy under reduced conditions and in Sapropel under oxidized conditions.

L'acidose ruminale est l'une des préoccupations majeures des exploitations laitières actuelles. Les levures vivantes (LV) ont été largement étudiées et utilisées chez les vaches laitières pour stabiliser la fermentation ruminale. Récemment, la mesure du potentiel redox ruminal (Eh, en mV) a été considérée comme un outil intéressant pour indiquer le trouble de la fermentation ruminale. L'effet positif de LV sur Eh ruminal a été rapporté, mais il reste variable selon les conditions expérimentales. Les objectifs de ce travail étaient de fournir une meilleure compréhension du mode d'action de LV et de définir la condition optimale de l'utilisation de LV chez les vaches laitières. La première partie de ce travail a consisté en une analyse quantitative des résultats de 22 expériences avec des vaches laitières canulées. La deuxième partie de ce travail a consisté à vérifier certains des résultats de l'analyse quantitative par une expérience chez des vaches en lactation. En utilisant l'analyse quantitative de données existantes provenant d'expériences antérieures, nous avons clarifié la relation entre le Eh ruminal et d'autres paramètres ruminaux principaux tels que le pH et le profil VFA, et suggéré que les variations de Eh pourraient être liées au transfert d'électrons dans les réactions dans le rumen. En outre, la réponse du Eh après la supplémentation en LV était également liée à celle du profil AGV ruminal, suggérant que l'effet de LV sur le profil VFA était atteint par l'augmentation du pouvoir réducteur, reflétant un meilleur transfert d'électrons dans le rumen. L'analyse a en outre démontré que la régulation du Eh ruminal par LV serait particulièrement efficace lorsque le risque de troubles digestifs est élevé. Puisque l'influence des caractéristiques de la ration sur le Eh ruminal a été quantifiée, l'effet de LV dans un régime donné pourrait être estimé indirectement. En outre, l'analyse quantitative a également révélé que la réponse de Eh suite à la supplémentation en LV était associée à la quantité de sucres solubles ingérée. L'expérience in vivo chez des vaches en début de lactation a confirmé un effet plus important de LV sur Eh ruminal avec une ration riche en sucres solubles, et a démontré que la supplémentation en LV avait un impact sur la richesse des bactéries, et que les métabolites ont également été influencés par la supplémentation en LV, probablement associée à la diminution du Eh ruminal. / Ruminal acidosis is one of the major concerns of current dairy farms. Live yeasts (LY) have been extensively studied and used in dairy cows for stabilization of rumen fermentation. Recently, measurement of ruminal redox potential (Eh, in mV) has been considered as an interesting tool to indicate ruminal fermentation disorder. The positive effect of LY on ruminal Eh has been reported, but it remains variable according to the experimental conditions. The aims of this work was to provide better understanding of mode of actions of LY, and to define the optimal condition of LY utilization in dairy cows. The first part of this work consisted to quantitative analysis of existing results from 22 experiments with cannulated dairy cattle. The second part of this work consisted to verify some of the results from quantitative analysis by an in vivo experiment in lactating cows. By using quantitative analysis of existing data from previously conducted experiments, we clarified the relationship between ruminal redox and other main ruminal parameters such as pH and VFA profile, and suggested that Eh variations might be related to the transfer of electrons in the reactions producing VFAs in the rumen. Moreover, response of ruminal Eh following live yeast supplementation was also related to that of ruminal VFA profile, which suggested that the effect of LY on VFA profile was achieved via the increase of reducing power, possibly reflected improved electron transfer and use in the rumen. The analysis further demonstrated that the regulation of ruminal Eh by LY would be particularly effective when risk of digestive disorder is high. Since the influence of dietary characteristics on ruminal Eh was quantified, the effect of LY in a given diet could be indirectly estimated. In addition, quantitative analysis also associated the response of ruminal Eh following LY supplementation to the intake of soluble sugars. The in vivo experiment in early-lactating cows confirmed greater effect of LY on ruminal Eh in diet rich in soluble sugars, and further demonstrated that i) LY supplementation tended to impact the richness of ruminal bacteria, and ii) some unidentified metabolites were also influenced by LY supplementation, probably associated to the decrease of ruminal Eh.