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.
Results
Showing 1 to 20 of 124 for “"biogeochemical cycles"”.
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Coupled Biogeochemical Cycles of Iron and Organic Carbon in Soils
… knowledge gap for understanding the coupled biogeochemical cycles of C and Fe.This study comprehensively investigated the amount and characteristics of Fe-bound OC in forest soils as well as the coupled biogeochemical reactions of Fe and OC during redox processes. Iron-bound OC contributed …
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Self sustained thermohaline oscillations and their implications for biogeochemical cycles
An ocean general circulation model (OGCM) configured with a paleo ocean bathymetry such as late Permian shows that different modes of ocean circulation might exist in warm climate: a strong 'thermal mode' induced by cooling at high latitudes and a weak 'haline mode' induced by evaporation at …
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Mechanistic models of oceanic nitrogen fixation
Oceanic nitrogen fixation and biogeochemical interactions between the nitrogen, phosphorus and iron cycles have important implications for the control of primary production and carbon storage in the ocean. The biological process of nitrogen fixation is thought to be particularly important where the …
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The large scale understanding of natural organic matter : processes and application
Natural biogeochemical cycles of the macronutrient elements carbon (C), nitrogen (N) and phosphorus (P) have been transformed by food and fuel production, through atmospheric pollution and climate change. Further, land disturbance has led to considerable losses of nutrients from terrestrial …
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High-frequency sensor data capture short-term variability in Fe and Mn cycling due to hypolimnetic oxygenation and seasonal dynamics in a drinking water reservoir
The biogeochemical cycles of iron (Fe) and manganese (Mn) in lakes and reservoirs have predictable seasonal trends, largely governed by stratification dynamics and redox conditions in the hypolimnion. However, short-term (i.e., sub-weekly) trends in Fe and Mn cycling are less well-understood, as …
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Cross-Scale Drivers of the Reciprocal Impacts Among Freshwater Mussels, Hydrology, and Floodplains on River Biogeochemistry
… the functional role of animal species in shaping biogeochemical cycles and resource patterns, therefore, it is necessary to account for variation in watershed features and hydrologic conditions. Freshwater mussels (Family: Unionidae) provide a valuable model system for examining the influence that …
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Environmental Causes of Pigment Heterogeneity In Phytoplankton Species
… phytoplankton species is important to understand biogeochemical cycles and the pelagic food chain system in the ocean, which could be manipulated by several environmental influences including nutrient availability, temperature, carbon dioxide levels, and light availability. Environmental …
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Distributional models of ocean carbon export
… aspect of marine microbial ecology and biogeochemical cycles. Particle flux is also variable and intricately complex, impeding its mechanistic or quantitative description. In this thesis we pair compilations of available data with novel mathematical models to explore the relationships …
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Uncovering Mechanisms of Phytoplankton Response to Climate Change
… into predicting how marine food webs and biogeochemical cycles may be altered by climate change.
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Coupled cycling of metals with nitrogen and carbon in marine sediments
… complex and often understudied components within biogeochemical cycles. In this thesis, I use stable isotopes of carbon, nitrogen, and oxygen as the primary tools to interrogates these complex reactions. First, I report abiotic oxidation of nitrite to nitrate by manganese(III)-pyrophosphate. This …
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Coupled cycling of metals with nitrogen and carbon in marine sediments
… complex and often understudied components within biogeochemical cycles. In this thesis, I use stable isotopes of carbon, nitrogen, and oxygen as the primary tools to interrogates these complex reactions. First, I report abiotic oxidation of nitrite to nitrate by manganese(III)-pyrophosphate. This …
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Soil bacterial structure and function associated with the invasive grass Microsteguim vimineum and two native grasses
Soil microorganisms play vital roles in biogeochemical cycles and are necessary for maintaining soil health. An invasive plant that alters the structure and function of the soil microbial assemblage could gain an advantage over native plants, enhancing its ability to invade new habitats, alter …
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Bioproducts and environmental quality: biofuels, greenhouse gases, and water quality
… fossil fuels, they may exacerbate other parts of biogeochemical cycles, notably nutrient loads in the aquatic environment. In three essays, this dissertation explores the tradeoff between GHG emissions and nitrogen leaching associated with biofuel production using general equilibrium models. The …
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Organic geochemistry and stable isotope constraints on Precambrian biogeochemical processes
Details of the biogeochemical cycles and the dominant mechanisms present in Precambrian remain heavily debated topics. The events of the Late Proterozoic onset to glaciations and what types of early life existed in the Archean are two of the many provoking topics within the Precambrian. We set out …
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A determination of air-sea gas exchange and upper ocean biological production from five noble gases and tritiugenic helium-3
… matching the time scales of many relevant biogeochemical cycles. The time-series of helium isotopes, tritium, argon, and oxygen was used to constrain upper ocean biological production. Specifically, the helium flux gauge technique was used to estimate new production, apparent oxygen …
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A Field and Modeling Assessment of Methyl Mercury Accumulation in an Engineered Retention Pond
… and changing lake characteristics impact lake biogeochemical cycles, and therefore, MeHg production and transport. A field and modeling analysis was performed on a small suburban lake located on the University of Connecticut campus to determine the impact of lake characteristics on the …
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Phase Speciation of Carbohydrates and Dioxins in Rivers and Coastal Waters in the Northern Gulf of Mexico
… organic matter and play an important role in biogeochemical cycles of carbon and other trace elements in marine environments. This study aimed to examine the abundance and partitioning of CHO between dissolved and particulate phases and their seasonal variations in the Mississippi Sound/Bight …
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Organic matter remineralization in coastal sediments in and around Kane‘ohe Bay, Hawaiʻi
Nutrient cycles in shallow, near shore environments can be profoundly influenced by sediments, via the burial or release of nutrients through organic matter (OM) remineralization during diagenesis. The decomposition and burial of OM in sediments are key processes influencing biogeochemical cycles …
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From Continental Margins to the Deep Ocean
… ~9% of the ocean but strongly influence marine biogeochemical cycles. The response of these zones to climate change 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 …
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A determination of air-sea gas exchange and upper ocean biological production from five noble gasses and tritiugenic helium-3
… matching the time scales of many relevant biogeochemical cycles. The time-series of helium isotopes, tritium, argon, and oxygen was used to constrain upper ocean biological production. Specifically, the helium flux gauge technique was used to estimate new production, apparent oxygen …
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