Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 16 of 16 for “"Iron Speciation"”.
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Influence of Iron Speciation on Redox Cycling and Reactivity With Persistent Organic Contaminants
… were used as surrogate models for studying iron-mediated redox processes. Initially, the redox reactivity of Fe II-organic ligand complexes with nitro-organic explosives was investigated. Ligand-screening experiments demonstrate that organic ligands containing catechol, thiol, and …
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Determination of Dissolved Iron Speciation in the North East Atlantic Ocean by Flow Injection Chemiluminescence
The knowledge of iron biogeochemistry is constrained by paucity in the understanding of its uptake, transport and the partitioning of the element between different phases, redox states and coordination sites. The work presented in this thesis describes the optimisation and evaluation of a Flow …
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Marine Deoxygenation Predates the End-Triassic Mass Extinction Within the Equatorial Panthalassa and its Influence on Marine Ecosystems Before the Biotic Crisis
… is thought to have been caused by a series of environmental changes triggered by the emplacement of the Central Atlantic Magmatic Province (CAMP). While the overall driver of the ETME is well-accepted, the specific roles of subsequent environmental changes in driving the extinction remain …
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Biogeochemical Cycling and Paleoenvironmental Reconstructions of the Toarcian Oceanic Anoxic Event from Western North America
… is thought to have resulted in significant environmental change. Associated with this interval was the widespread deposition of organic-rich sediments, carbon cycle and seawater chemistry changes, global warming, the development of marine anoxia, and major extinction events. The majority of …
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A multiproxy investigation of oceanic redox conditions during the Cambrian SPICE event
… across a range of spatial scales using the iron speciation paleoredox proxy to characterize redox conditions within individual basins and to facilitate comparison of conditions between basins. In addition to these analyses, we apply a new proxy, thallium stable isotopes to this interval to …
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From Continental Margins to the Deep Ocean
… redox proxies. This thesis examines three environments: the Peruvian Margin (continental margin), the Guaymas Basin (semi-restricted), and Pacific Gyres (oxic pelagic, ~90 Myr). Proxies such as iron speciation, Mo and U concentrations, and isotopes (δ98Mo, δ15N) were used to reconstruct redox …
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An integrated geochemical and sedimentological analysis of a lacustrine Lagerstätten in the Triassic Cow Branch Formation of the Dan River Basin
… total organic carbon (TOC), pyrite sulfur and iron speciation data suggest anoxic, ferruginous waters. At the lagerstätte interval, TOC content increases significantly, coinciding with the presence of darker, more laminated sedimentary lithofacies. At the interval of the highest TOC content, a …
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Geochemical investigations of the late early Cambrian extinctions
… straightforward interpretation. In addition, iron speciation and mercury content analyses from the Flatwoods Member within the stratigraphic interval tentatively linked to the olenellid extinction suggest the occurrence of transient local euxinic (anoxic, sulfidic) conditions. These findings …
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SUSTAINABLE CATALYSIS VIA IRON AND ZINC COMPLEXES: FROM TUNABLE METALLATE SYSTEMS TO PHOTOCHEMICAL REACTIVITY
This thesis investigates the use of iron and zinc complexes as sustainable catalysts for transformations of small, strained heterocycles in the field of carbon dioxide valorization, as well as the synthesis of iron complexes as catalysts for photochemical oxidation. In the first part of the work, …
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Paleoecology and Taphonomy of Ediacaran macrofossils from the Khatyspyt Formation, Olenek Uplift, Siberia
… taphonomic history, ecology, and paleoenvironmental distribution. Thus, new ways of investigation need to be employed to unveil enigmas of Ediacaran organisms. As well as, scientists need to engage other representatives of Ediacaran assemblages, such as macroalgae, to fully understand how …
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Molecular determination of marine iron ligands by mass spectrometry
… of biologically important metals such as iron, copper, cobalt, and zinc. In marine environments where the availability of iron limits microbial growth and carbon fixation rates, the ability to access organically bound iron confers a competitive advantage. Thus, the compounds that microbes …
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Cloud Chemical Heterogeneity and Its Influence on Aqueous sulfur(IV) Oxidation
… hydroxymethanesulfonate (HMS) and trace metals iron and manganese were measured. Samples were collected with three cloud samplers capable of partitioning the cloud drop size spectrum into two or three independent drop size fractions. Measurements of pH variations within natural cloud drop …
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Molecular determination of marine iron ligands by mass spectrometry
… of biologically important metals such as iron, copper, cobalt, and zinc. In marine environments where the availability of iron limits microbial growth and carbon fixation rates, the ability to access organically bound iron confers a competitive advantage. Thus, the compounds that microbes …
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Evaluating redox cycling across the Toarcian Oceanic Anoxic Event with implications for paleo-environmental reconstructions and organic matter sulfurization
… can result in changes in the carbon, sulfur, and iron cycles on our planet. Changes in these elemental cycles lead to distinctive variation in the chemical composition of seawater that is recorded in marine sediments that are preserved into the sedimentary record. Our modern ocean is experiencing …
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The Fate and Mobility of Heavy Metals in East Anglian Salt Marsh Sediments
… to reconstruct past redox conditions—such as the speciation of iron mineralogy, δ98Mo, and δ53Cr—rely on the assumption that the geochemical signature acquired at the sediment surface is translated directly into the geologic record. In this thesis, I have used East Anglian salt marsh anoxic pond …
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Geochemical investigation of the co-evolution of life and environment in the Neoproterozoic Era
The co-evolution of life and the environment stands as a cornerstone in Earth's 4.5-billion-year history. Environmental fluctuations have wielded substantial influence over biological evolution, while life forms have, in turn, reshaped Earth's surface and climate. This dissertation centers on a …