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 20 of 93 for “"redox conditions"”.
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A multiproxy investigation of oceanic redox conditions during the Cambrian SPICE event
… 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 assess potential …
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Characterization of redox conditions in a petroleum contaminated aquifer: Implications for bioremediation potential
… of contaminant mass loss. The measurement of redox conditions and evaluation of TEAPs are critical in assessing the capacity for bioremediation at any site. A series of batch microcosm experiments, using sediment collected from a gasoline-contaminated aquifer at Fort McCoy, Wisconsin, was …
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Studying Redox Conditions of Devonian and Neoproterozoic Oceans Using I/ca Proxy From Bulk Carbonate Rocks
… an important trace element in biogeochemical and redox reactions. It has a nearly consistent concentration of ~0.46 μmol/L in the seawater and the inorganic speciation (IO3− and I−) of iodine is primarily controlled by redox conditions in water columns. Iodate (IO3−), not iodide (I−), is the only …
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Groundwater redox conditions at a petroleum contaminated site, Kuils River, South Africa : pathways for BTEX biodegradation
… field measurements of electrical conductivity, redox potential, and pH. The variation and distribution of these redox-sensitive groundwater constituents show that bioremediation via NO₃- reduction, Fe³+ reduction, and SO₄²- reduction (and possibly methanogenesis in the most reduced part of the …
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The Archean origin of assimilatory sulfate metabolisms provides novel insight into redox conditions of early Earth environments
… isotopic fractionations acting on distinct redox states (e.g. sulfate, sulfide, sulfite) for anabolism (Liu et al., 2012). An assimilation pathway exists, which starts with sulfate adenylyltransferase (sat/ATP sulfurylase) catalyzing a reaction of adenosine triphosphate (ATP) and sulfate …
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Provenance, redox conditions, and diagenesis of shales in Chang 7 member of Upper Triassic Yanchang Formation, Ordos Basin, China
<p>“This study aims to decipher provenance, redox conditions, and burial history of shales in Chang 7 Member of Upper Triassic Yanchang Formation, Ordos Basin, China. The first paper discusses the origins of single-channeled, vertical, sinuous, and calcite-bitumen-filled cracks in the shales. …
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Reconstructing local redox conditions, mineral precipitation processes and nutrient availability in seawater during deposition of the Transvaal Supergroup, South Africa
… The chemistry of ancient oceans influenced iron redox states and primary mineral precipitation, affecting the cycling of other trace elements and nutrients. While carbonate minerals are commonly used as geochemical archives, reconstructions using IF have proved more challenging, with many studies …
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Development of New Methods to Control Redox Conditions in High-pressure Experiments and their Application to Study Ore Metal Solubilities in Sulfur-bearing Magmatic Fluids
… values in hydrous experiments. Using CoPd alloy redox sensors, the method was shown to be accurate within 0.3 log units for the P-T range of 960 – 2060 bar and 800 – 1100⁰C. The rate of progressive oxidation caused by diffusive H2 loss through the Molybdenum Hafnium Carbide (MHC) pressure vessel …
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The Influence of Hydrogeomorphology, Soil Redox Conditions, and Salinity on the Spatial Zoning of Saltgrass, Salt Rush, and Cattails in Scotts Creek Marsh, Swanton Pacific Ranch, CA
… Creek Marsh, (ii) soil oxidation and reduction (redox) conditions, (iii) salinity, and (iii) the effectiveness of Adobe Photoshop CS 5.1 (AP5) to analyze IRIS images. All three halophytes were well suited for anoxic, redox, and saline conditions by utilizing morphological adaptations (arenchyma, …
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From Continental Margins to the Deep Ocean
… is uncertain, making reconstructions of past redox conditions, to better understand the future, essential. For this porpose, redox-sensitive proxies are widely used, but their signals can be altered by depositional and diagenetic processes. In this thesis, we investigate the behavior of these …
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Shallow Groundwater Quality in Alberta (Canada) with a Focus on the Occurrence of Nitrate and Methane
… study characterized the hydrogeochemistry and redox state of shallow groundwater (< 150 mbgs) in Alberta, with a focus on the occurrence of nitrate and methane. Chemical analyses of > 60,000 groundwater samples collected from landowner wells (part of the Alberta Health Services dataset) were …
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OXIDE FILM FORMATION AND CONVERSION MECHANISM ON CARBON STEEL UNDER MILDLY BASIC CONDITIONS
… and hence, its kinetics depends on the aqueous redox condition and the physical and chemical nature of surface oxide formed during corrosion. Nuclear plant environment includes the additional challenge of fields of ionizing radiation that can affect the redox conditions in solution. To develop a …
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Controls on arsenic mobility in contaminated wetland and riverbed streams
… Geochemical modeling was used to predict redox conditions and As associations. We found that most As in the wetland was adsorbed onto amorphous Fe (hydr)oxide phases. Riverbed sediments differed from wetland sediments in that redox conditions were more reducing, and As was associated with …
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The Fate and Mobility of Heavy Metals in East Anglian Salt Marsh Sediments
Measuring the evolution of redox conditions in Earth’s atmosphere and oceans through time is a prominent challenge in Earth Sciences. Geochemical proxies in sedimentary rocks used to reconstruct past redox conditions—such as the speciation of iron mineralogy, δ98Mo, and δ53Cr—rely on the assumption …
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Eutrophication Assessment for Lyndon B. Johnson Lake, a Subtropical Reservoir in Central Texas: Impacts from Urbanization and Upstream Sources
… allowing for seasonal anoxia and low redox conditions nearly every year in the hypolimnion. These conditions resulted in internal loading of nitrogen and phosphorus. At the other stations, the seasonal development of water column stability was weakened or completely inhibited during …
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Physical, chemical, and microbial dynamics in the hyporheic zone
… ways in which hyporheic zone dissolved oxygen conditions respond to surface channel flow perturbations. I show that the surface channel flow velocity exerts a strong influence on hyporheic dissolved oxygen conditions, that there is lag between surface channel flow perturbations and response in …
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Investigating chromium cycling in global oxygen deficient zones with chromium isotopes
… isotopes have shown great potential as a paleo-redox proxy to trace the redox conditions of ancient oceans and atmosphere. However, its cycling in modern environments is poorly constrained. In my thesis, I attempt to fill in the gap of our understanding of chromium cycling in the modern ocean, …
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Isotopes of selenium as redox tracers of geochemical processes influencing the export and behavior of selenium contamination in coal mine watersheds
Selenium is a redox-active element that is necessary for life in small quantities but causes toxic effects for wildlife above 5 μg/L in water and for humans above 50 μg/L in drinking water. Se contamination is released by oxidative weathering of Se-bearing shales, and this contamination is often …
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Investigating Chromium Cycling in Global Oxygen Deficient Zones with Chromium Isotopes
… isotopes have shown great potential as a paleo-redox proxy to trace the redox conditions of ancient oceans and atmosphere. However, its cycling in modern environments is poorly constrained. In my thesis, I attempt to fill in the gap of our understanding of chromium cycling in the modern ocean, …
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Evaluating rhizodegradation of petroleum hydrocarbons and polycyclic aromatic hydrocarbons in wetland sediments containing spartina patens
… for PHC, PAH, microbial density, nutrients, pH, redox and root biomass at 2.5 and 7.5 cm in sediments with <12% PHC. The sediments contained on average 6.5% to 9.5% PHC and 56 to 124 parts per million (ppm) total PAH. The plants exhibited a 95% survival rate and added from 1% to 2% root biomass …
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