Submitted by Haroudo Xavier Filho (haroudo.xavierfo@ufpe.br) on 2016-04-06T16:47:08Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Carolina Rodrigues Gonzalez.pdf: 1642358 bytes, checksum: 3c6e27247b71fe24781e9ffe5a5add91 (MD5) / Made available in DSpace on 2016-04-06T16:47:09Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Carolina Rodrigues Gonzalez.pdf: 1642358 bytes, checksum: 3c6e27247b71fe24781e9ffe5a5add91 (MD5) Previous issue date: 2015-07-30 / CAPES / A matéria orgânica do solo (MOS) é uma componente importante na sustentabilidade dos sistemas nativos e antropizados. A manutenção da MOS é necessária para estabelecer práticas de manejo sustentáveis e que otimizem a produção agropecuária. No semiárido brasileiro, a maior dificuldade para estabelecer práticas de manejo adequado está na lacuna de conhecimento em relação à dinâmica da MOS sob as variadas condições edafoclimáticas, características da região. A modelagem dos processos biogeoquímicos é uma importante ferramenta que permite a compreensão da dinâmica da MOS no sistema solo-planta de forma prática, além de permitir projetar cenários futuros e, assim, embasar tomadas de decisões. O modelo CENTURY tem sido utilizado em vários ecossistemas e em diversos tipos de uso da terra para simular a ciclagem biogeoquímica de carbono, nutrientes e água. O presente estudo teve como objetivo avaliar o desempenho do modelo previamente calibrado para uma área de catinga no município de Santa Teresinha, PB, para simular os estoques de C e N em áreas de caatinga densa na região semiárida de Pernambuco. Para isso, foram utilizadas as informações dos estoques de C e N no solo e na vegetação coletados em áreas de caatinga sob seis classes de solo (Planossolo, Argissolo, Neossolo Litólico, Neossolo Regolítico, Luvissolo e Latossolo), em 25 pontos distribuídos pelo Agreste e Sertão de Pernambuco. O modelo previamente calibrado por Althoff (2015), foi rodado para as áreas de caatinga densa selecionadas, com alterações apenas nos valores característicos de cada local como dados históricos de temperatura e precipitação mensais médias, coordenadas geográficas, textura, densidade, profundidade e o conteúdo de rochas do solo. Os principais dados de saída avaliados foram os estoques de C e N no solo e o carbono na biomassa aérea e subterrânea. O modelo demonstrou melhor desempenho para simular o estoque de C no solo (0-20 cm) em áreas de caatinga densa no sertão oeste de Pernambuco. Ajustes no modelo resultaram em melhorias na simulação do estoque no solo no agreste. Os resultados mostram que o modelo calibrado para uma região específica da caatinga possui abrangência limitada. Portanto, há a necessidade de mais esforços para calibração do modelo com capacidade de simulação mais ampla dos estoques em outras áreas da caatinga. / Soil organic matter (SOM) is an important component to ensure the sustainability of native and anthropogenic systems. Maintaining of the SOM levels is important to establish sustainable management practices and to improve agricultural production. In the Brazilian semiarid region, the greatest difficulty to establish proper management practices is the lack of knowledge about the dynamics of SOM under different soil and climatic conditions that are characteristics of the region. The modeling of biogeochemical processes is an important tool for the SOM dynamics understanding in the soil-plant system in a practical way, and allows project future scenarios and thus to base public decisions. The CENTURY model demonstrated efficiency in simulate conditions in various ecosystems and different types of land use to simulate the carbon biogeochemical cycling, nutrients and water. The present study aimed to evaluate the performance of the model that were calibrated for a “caatinga” site in Santa Teresinha, PB, in simulate the stocks of C and N in areas of dense scrub in the semiarid region of the Pernambuco state. For this study, we used the information of C and N stocks in soil and vegetation collected in areas of “caatinga” under six soil classes (Planosol, Argisol Udorthent, Entisol, Luvisol and Latosol), 25 points distributed by Wasteland and Hinterland of Pernambuco. We used the model previously calibrated by Althoff (2015), and we run it in the areas of dense scrub selected. We changes only the specific characteristics values of each site, like historical temperature and average monthly rainfall, geographic coordinates, texture, density, depth and content soil rocks. The main data of this output were the stocks of C and N in the soil and the carbon in the shoot and root biomass. The model showed better performance to simulate the stock of C in the soil (0-20 cm) in areas of dense scrub in western hinterlands of Pernambuco. Adjustments in the model results in improvements in the simulation of the stock on the ground in the wild. Century model calibrated for a specific region of the savanna has limited scope. So is needed more efforts to model calibration with larger capacity of simulate stocks in other areas of the savanna.

No description available.

For decades the Baltic Sea has been subject to eutrophication due to heavy anthropogenic nutrient loads on the aquatic ecosystem. Quantitative projections of its effects require an understanding of its driving mechanisms, i.e., the hydrodynamics that are responsible for the physical transport and mixing and the biogeochemical nutrients pathways within the algal ecosystem and between the particulate and dissolved phases in the water and in the sediments. A simple basin-scale hydrodynamic framework is set for the Gulf of Finland to test different descriptions of the biogeochemical transformations and determine the most robust modelling strategy. A recently developed criterion to determine the occurrence of anoxic events, based on the amount of fresh carbon detritus in the sediments is implemented in comparison with the classical criterion based on the oxygen concentration in the bottom water. Time-averaging of the hydrodynamics over larger than daily intervals is proved to hinder the capture of rapid mixing events jeopardizing irremediably the water quality simulation. The new carbon based criterion for anoxia shows a better dynamic response and is less sensitive to the model’s internal parameters. An internal source in the sediments correlated to the amount of fresh detritus, to represent the release of iron-bound phosphorus is confirmed as a versatile modelling assumption.

Thesis: Ph. D., Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references. / This thesis examines the controls on organic, inorganic, and volatile species distributions in hydrothermal fluids venting at Von Damm and Piccard, two recently discovered vent fields at the ultra slow spreading Mid-Cayman Rise, Earth's deepest mid-ocean ridge. A wide variety of possible temperatures and substrates for fluid/rock reaction exist at ultraslow spreading ridges. The flux of chemicals delivered to the ocean by circulating vent fluids exerts a major control on mass transfer into and out of the oceanic crust and supports chemosynthetic ecosystems. In Chapter 2, abiotic organic synthesis is shown to occur via two distinct mechanisms in the serpentinizing Von Damm system. Longstanding questions concerning the spatial, temporal, and mechanistic nature of carbon transformations in deep-sea hot springs are addressed. In contrast with the current paradigm, CH4 is not actively forming during circulation of H2-rich vent fluids, but instead is derived from fluid inclusions in the host rocks. Chapters 3 and 4 present in-depth studies of the chemical and isotopic compositions of aqueous species in vent fluids at Von Damm and Piccard to elucidate the role of reaction temperature, pressure, substrate composition, and water/rock mass ratios during the chemical evolution of hydrothermal fluids at oceanic spreading centers. At Von Damm, sequential reaction of gabbroic and peridotite substrates at intermediate temperatures can explain generation of the observed fluids. Geochemical modeling shows that talc-quartz assemblage is expected to precipitate during fluid mixing with seawater at the seafloor. At Piccard, extremely high temperature subsurface water/rock reaction results in high temperature fluids that are richer in dissolved H2 than any previously observed fluids worldwide. At both locations, high-H2 conditions promote the abiotic reduction of [Epsilon]CO2 to formate species, which may fuel a subsurface biosphere. In Chapter 5, multiple sulfur isotopes were measured on metal sulfide deposits, So, and fluid H2S to constrain sulfur sources and the isotopic systematics of precipitation in a wide variety of seafloor hydrothermal vents. Areas studied include the eastern Manus Basin and Lau Basin back-arc spreading centers, the unsedimented basalt-hosted Southern East Pacific Rise, and the sediment-hosted Guaymas Basin mid-ocean ridge spreading centers. Limited isotope fractionation between fluid H2S and precipitating chalcopyrite implies that sulfur isotopes in a chimney lining may record past hydrothermal activity. / by Jill Marie McDermott. / Ph. D.

Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007. / Includes bibliographical references. / Zinc (Zn) stable isotopes can record information about important oceanographic processes. This thesis presents data on Zn isotopes in anthropogenic materials, hydrothermal fluids and minerals, cultured marine phytoplankton, natural plankton, and seawater. By measuring Zn isotopes in a diverse array of marine samples, we hope to understand how Zn isotopes are fractionated in the oceans and how Zn isotopes may be used as tracers of marine biogeochemical processes. Common forms of anthropogenic Zn had [delta]66Zn from +0.08 %o to +0.32 %o, a range similar to Zn ores and terrigenous materials. Larger variations were discovered in hydrothermal fluids and minerals, with hydrothermal fluids ranging in 666Zn from 0.02 %o to +0.93 %o, and chimney minerals ranging from -0.09 %o to +1.17 %o. Lower-temperature vent systems had higher [delta]666Zn values, suggesting that precipitation of isotopically light Zn sulfides drives much of the Zn isotope fractionation in hydrothermal systems. In cultured diatoms, a relationship was discovered between Zn transport by either high-affinity or low-affinity uptake pathways, and the magnitude of Zn isotope fractionation. We established isotope effects of [delta]66Zn = -0.2 %o for high-affinity uptake and [delta]66Zn = -0.8 %o for low-affinity uptake. This work is the first to describe the molecular basis for biological fractionation of transition metals. Biological fractionation of Zn isotopes under natural conditions was investigated by measuring Zn isotopes in plankton collected in the Peru Upwelling Region and around the world. / (cont.) Seawater dissolved Zn isotopes also reflect the chemical and biological cycling of Zn. The [delta]66Zn of deep seawater in the North Pacific and North Atlantic is about 0.5%0, and the dissolved [delta]66Zn gets lighter in the upper water column. This is unexpected based our observations of a biological preference for uptake of light Zn isotopes, and suggests that Zn transport to deep waters may occur by Zn adsorption to sinking particles rather than as primary biological Zn. The thesis, by presenting data on several important aspects of Zn isotope cycling in the oceans, lays the groundwork for further use of Zn isotopes as a marine biogeochemical tracer. / by Seth Greeley John. / Ph.D.

Thesis: Ph. D., Joint Program in Marine Geology and Geophysics (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Here I use a simple numerical model of reef profile evolution to show that the present-day morphology of carbonate islands has developed largely in response to late Pleistocene sea level oscillations in addition to variable vertical motion and reef accretion rates. In particular, large amplitude 'ice-house' sea-level variability resulted in long lagoonal depositional hiatuses, producing the morphology characteristic of modern-day barrier reefs. Reactivation of carbonate factories, transport of coarse reef material and rapid infilling of shallow water accommodation space since deglaciation makes these unique sites for reconstructing Holocene climate. Integration of new tropical cyclone reconstructions from both back-barrier reef (central Pacific) and carbonate bank (the Bahamas) settings with existing storm archives suggests a coordinated pattern of cyclone activity across storm basins since the late Holocene. Seesawing of intense tropical cyclone activity between the western Pacific (-0- 1000 yrs BP) and North Atlantic/Central Pacific (~1000 ~2500 yrs BP) appears closely tied with hydrographic patterns in the tropical Pacific and El Niflo-like variability. Decoupling of North Atlantic (inactive) and South Pacific (active) tropical cyclone patterns during the mid-Holocene suggests precession driven changes in storm season insolation may constrain ocean-atmosphere thermal gradients and therefore cyclone potential intensity on orbital timescales. / by Michael Toomey. / Ph. D.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007. / Includes bibliographical references. / Basaltic ocean crust has the potential to host one of the largest endolithic communities on Earth. This portion of the biosphere, however, remains largely unexplored. In this study, we utilize molecular biological, microscopic, and geochemical tools to gain a better understanding of the geomicrobiology of the ocean crust. Specifically, we examine the phylogenetic diversity of microorganisms inhabiting basaltic lavas, the activities and abundances of these microorganisms, the spatial extent of the biosphere, and the potential effect that microbial activity has on the geochemistry of the ocean crust and overlying water column. Our study demonstrates that young, fresh volcanic lavas near mid-ocean ridges host an incredibly diverse and dense population of microorganisms dominated by Bacteria, quite distinct from the microbial communities found in surrounding deep seawater and hydrothermal vents. Furthermore, these communities may contribute to the elemental cycling of Fe, S, Mn, N, and C in this environment. The inability to definitively identify microorganisms in drill-cores of old (> 15 Ma) ocean crust, however, implies that these once prolific communities may become scarce as the crust ages and moves further away from the ridge axis. Finally, we provide evidence suggesting that these communities are fueled by oxidative alteration reactions occurring in the basaltic crust. / by Cara M. Santelli. / Ph.D.

O estado de Rondonia possui hoje o 8° maior rebanho bovino do pais. Essa caracteristica o torna urn estado essencialmente pecuarista, muito embora ja se perceba um avanco na atividade agricola. Em termos de impacto ambiental, a pecuaria é extremamente agressiva, pois nas praticas antigas de manejo do gado era comum a conversdo direta da floresta em pastagem e consecutivas queimas nos primeiros anos para a limpeza da biomassa remanescente da floresta. Este trabalho tem por objetivo avaliar possiveis alteracOes na biogeoquimica das aguas do rio Urupd mediante esse cenario de contraste entre areas que preservam as caracteristicas naturais e areas corn elevado grau de perturbacao. Corn este intuito, foram realizadas amostragens em seis pontos ao longo do rio Urupd, de forma a termos um gradativo cendrio de perturbacdo no use do solo. 0 primeiro ponto refere-se ao setor da nascente, e é o mais preservado da bacia, corn praticamente 100% de suas caracteristicas naturais, ao passo que o Ultimo, que abrange toda a bacia de drenagem, mantem aproximadamente 51% de floresta. Para essas unidades de drenagens foram analisadas as concentraeOes de ions maiores (Nat, Kt, Mg2+, Ca2+, HCO3\", CY e SO42), de carbono organic° dissolvido (COD), e a razao isotOpica do carbono inorganic° dissolvido (613C do CID). Em geral, os resultados mostraram que, apesar da quantidade de pastagem aumentar de uma unidade de drenagem para outra, e as concentracCies de ions dissolvidos aumentarem consideravelmente, as diferencas nas concentracOes apresentam melhor relacdo coin a distribuicao da Capacidade Efetiva de Troca de Cations, caracteristica inerente dos solos. Portanto, em termos das concentracOes de ions maiores, apesar do extenso desmatamento, ndo ha indicios de que os processos naturais tenham sido suplantados por antropogenicos como principais fatores determinantes da dinamica neste sistema. Contudo, a distribuicdo espacial e temporal das concentraceies de carbono organic° dissolvido demonstram que o aumento do percentual de pastagens relaciona-se corn concentracOes significativamente maiores desta forma de C nas aguas do canal principal. A composicao isot6pica (613C) do carbono inorganic° dissolvido demonstrou que, nos setores mais a juzante da bacia do rio Urupd, a quimica das aguas e predominantemente determinada por processos de intemperismo de rochas carbonatadas / The state of Rondonia has the 8th largest cow herd of the country. This characteristic makes it a state where cattle raising dominates the landscape, although other agricultural uses are becoming noticeable. In terms of environmental impacts cattle raising is extremely aggressive, since early practices were based on slash and burn techniques. This study intends to evaluate changes in the biogeochemistry of the Urupá river waters in such a scenario of remaining pristine areas and heavily impacted ones. In order to understand that, 6 sampling stations were established along the river, at different degrees of land use changes. The first station refers to the headwaters and is the most pristine reach, with almost 100% of its original vegetation, whereas the the last corresponds to the whole basin and has only 51% or remaining forests. The waters where analyzed for the concentrations of major ions (Na+, K+, Mg2+, Ca2+, HCO3-, Cl- e SO42-), dissolved organic carbon (DOC) and the isotopic composition (?13C) of dissolved inorganic carbon (DIC). Generally, the results show that, although the percentages of pasture and major ion concentrations increase significantly along the basin, the latter relates better with a natural characteristic of the soils, which is the effective cation exchange capacity. Consequently, in terms of the ionic concentration of these waters, even with the extensive deforestation observed in the basin, it is not possible to conclude that anthropogenic processes have overcome natural ones as main forces driving the dynamics of this system. However spatial and temporal DOC distributions show that pastures are directly related to increases of this form of C in these waters. DIC isotopic composition (?13C) shows that the chemistry of the Urupá river lower reaches is controlled by the weathering of carbonate rocks

De nombreux écosystèmes forestiers français sont développés sur des sols acides et pauvres en éléments nutritifs. Dans de nombreux contextes, la fertilité minérale de ces sols forestiers se dégrade lentement, en lien notamment avec des pressions extérieures passées ou actuelles (e.g. diminution des apports atmosphériques de nutriments, augmentation des exportations de biomasse). Ce constat préoccupe la communauté forestière et des solutions de restauration/remédiation sont souvent envisagées. L’amendement avec un produit carbonaté est une pratique connue pour réduire l'acidité du sol, améliorer le fonctionnement global de l'écosystème et compenser les pertes de nutriments causées par la récolte de biomasse. Cependant, les effets de l’amendement sur les processus et le cycle biogéochimique du calcium et magnésium dans les écosystèmes forestiers sont peu connus à ce jour. Cette étude se focalise sur le devenir du magnésium et du calcium provenant de la dissolution des produits d’amendement dans cinq hêtraies situées dans le nord de la France sur une période allant jusqu’à 45 ans après l’apport. Pour cela, les approches élémentaires « conventionnelles » ont été combinées avec une approche multi-isotopique (26/24Mg, 44/40Ca et 87/86Sr). Les données provenant des parcelles témoins mesurées tout au long de la période d'étude suggèrent, quel que soit le site considéré, que les pools échangeables de cations nutritifs dans le sol ont diminué sur les dernières décennies et que cette tendance, associée à la faible richesse chimique du sol, se reflète dans la nutrition foliaire (Ca, Mg, K, P). En comparaison des placettes témoins, les pools échangeables de Mg et de Ca dans l’horizon 0-40 cm du sol ont augmenté dans les placettes amendées durant la première décennie après l’amendement, mais les différences s’estompent après 20 à 30 ans. Cependant, l'effet de l’amendement sur la nutrition des arbres est encore observé 40 ans après l’apport, très probablement parce que le cycle biologique de ces éléments a été dynamisé par l’amendement. La réponse des écosystèmes à l’amendement varie d'un site à l'autre, en fonction de la nature du produit (CaCO3 ou Ca-MgCO3) et du niveau de richesse chimique initial du sol, les sites les plus pauvres chimiquement enregistrant les réponses les plus marquées. Les variations naturelles des rapports isotopiques du Mg, Ca et Sr, en complément des approches conventionnelles, mettent en évidence l’importance de la composante Bio des cycles biogéochimiques du Ca et Mg dans ces hêtraies à faible fertilité minérale. Ces outils isotopiques ont également permis de démontrer l'incorporation durable de Ca et Mg issus des produits d’amendement dans leur cycle biologique respectif et de mettre en évidence des modifications de fonctionnement biogéochimique des écosystèmes suite à l’amendement / In France, many forest ecosystems grow on acidic and nutrient poor soils. In numerous cases, the chemical fertility of forest soils is slowly degrading due to increasing external pressures (e.g. decreasing atmospheric inputs, increasing biomass exportations) and is a growing concern in the international forest community. Forest management often must resort to restauration/remediation practices to ensure the sustainability of the ecosystem. Forest liming with a carbonate product is a known practice to reduce soil acidity, globally improve the ecosystem functioning and compensate nutrient losses caused by biomass harvest and exportation. However, our understanding of the effects of liming on magnesium and calcium biogeochemical processes and cycling in forest ecosystems is still incomplete. This study focuses on the fate of magnesium and calcium originating from the dissolution of liming products in the soils and trees of five beech forests located in Northern France over a period up to 45 years. In order to do so, “conventional” total-element approaches were combined with a multi-isotopic approach (26/24Mg, 44/40Ca et 87/86Sr). At all five sites, the data measured in control plots throughout the study period suggest that the exchangeable pools of nutrient cations in the soil has decreased over the last several decades and that this trend, together with the low chemical fertility level of the soil, was reflected in foliar nutrition (Ca, Mg, K, P). Compared to the control plots, soil exchangeable pools of Mg and Ca in the 0-40cm layer in the limed plots increased during the first decade after liming but differences were no longer observable in soil pools after 20 to 30 years. However, the effect of liming on tree nutrition was still observed after 40 years, most probably because the biological cycling of these elements was enhanced by the lime input. The ecosystem response to the lime input varied between sites depending on the nature of the liming product (CaCO3 or Ca-MgCO3) and the initial chemical fertility level of the soil, the poorest sites showing the strongest responses. The natural variations of Mg, Ca and Sr isotopic ratios combined with conventional approaches highlight the importance of the BIO component of the biogeochemical cycling of Mg and Ca in the studied low chemical fertility beech forests. These isotopic tools also enabled to show the long-lasting incorporation of the Mg and Ca released from the liming product in the biological cycle and highlight the changes in the biogeochemical functioning of these forest ecosystems after the liming operation

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Quorum sensing (QS) via acylated homoserine lactones (AHLs) was discovered in the ocean, yet little is known about its role in the ocean beyond its involvement in certain symbiotic interactions. The objectives of this thesis were to constrain the chemical stability of AHLs in seawater, explore the production of AHLs in marine particulate environments, and probe selected behaviors which might be controlled by AHL-QS. I established that AHLs are more stable in seawater than previously expected and are likely to accumulate within biofilms. Based on this result, I chose to study AHLQS in the bacterial communities inhabiting biofilms attached to Trichodesmium spp. and detrital (photosynthetically-derived sinking particulate organic carbon, POC) particles. These hot spots of microbial activity are primary sites of interaction between marine primary producers and heterotrophs and crucial components of the biological pump. Biofilm communities associated with Trichodesmium thiebautii colonies in the Sargasso Sea differed considerably from seawater microbial communities. In addition, there was no overlap between the communities associated with tuft and puff colonies. These results suggest that bacterial communities associated with Trichodesmium are not random; rather, Trichodesmium selects for specific microbial flora. Novel 16S rRNA gene sequences are present both in clone libraries constructed from DNA extracted from colonies of Trichodesmium spp. and in culture collections derived from wild and laboratory cultivated Trichodesmium spp., supporting the idea that the phycosphere of Trichodesmium is a unique microenvironment. Using high performance liquid chromatography-mass spectrometry, I demonstrated that bacteria isolated from Trichodesmium synthesize AHLs. In addition, I detected AHLs in sinking particles collected from a site off of Vancouver Island, Canada. AHLs were subsequently added to laboratory cultures of non-axenic Trichodesmium colonies and sinking POC samples. This is the first time AHLs have been detected in POC and indicates that AHL-QS was occurring in POC. Further, I showed that AHLs enhanced certain organic-matter degrading hydrolytic enzyme activities. My results suggest that AHL-QS is a factor regulating biogeochemically relevant enzyme activities on sinking POC and within the biofilms attached to Trichodesmium colonies and thereby may impact the timing and magnitude of biogeochemical fluxes in the ocean. / by Laura Robin Hmelo. / Ph.D.