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 20 for “"Biogeochemical cycle"”.
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Modeling the Biogeochemical Cycle of Selenium in the San Francisco Bay
… and San Joaquin River inputs on the selenium cycle, the model ECoS 3 (distributed from Plymouth Marine Laboratory, United Kingdom) was modified to simulate the biogeochemical cycle of selenium in the Northern Reach. The model is designed to simulate salinity, total suspended material, …
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Exploring the microbe-mediated soil H² sink : a lab-based study of the physiology and related H² consumption of isolates from the Harvard Forest LTER
… The largest and least understood term in the H² biogeochemical cycle, microbe-mediated soil uptake, is responsible for about 80% of Earth's tropospheric H² sink. A recent discovery of the first H²-oxidizing soil microorganism (Streptomyces sp. PCB7) containing a low-threshold, high-affinity …
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The Distribution of Dissolved Barium Along the U.S. Geotraces North Atlantic Transect: Impact of Biogeochemical Processes, Circulation and Phase Association
… there has been a growing interest in the biogeochemical cycle of barium (Ba) due to its potential as a proxy for interpreting the geologic record. The typical barium distribution exhibits removal in the upper water column and regeneration at depth, consistent with its classification as a …
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Determination and speciation of mercury in sediment and related samples from Greece and Scotland
… Hg detection and improve understanding of its biogeochemical cycle and risks to human health. In this study, a simple, colorimetric method utilising the reaction of Hg with copper(I)iodide was characterised and adapted for screening marine samples, and the speciation and relationships of Hg …
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Thermal responses of marine phytoplankton: Implications to their biogeography in the present and future oceans
… as primary producers and as regulators of the biogeochemical cycle. However, some may form harmful algal blooms that are a global problem due to the production of toxins that pose a risk to public health, the environment, and our economy. Climate change poses a serious threat to phytoplankton …
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Modelling biogeochemical controls on planetary habitability
… star, and the operation of any (bio)geochemical cycles that may serve to regulate planetary climate. A stellar evolution model was developed to investigate the control of increasing main-sequence stellar luminosity on the boundaries of the radiative habitable zone, which was then coupled with a …
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Quantifying mercury surface fluxes by combining atmospheric observations and models
… concern. Although an important component of its biogeochemical cycle, large uncertainties still exist in the estimates of surface fluxes of mercury. Three projects presented in this thesis improve our understanding of mercury surface fluxes at different spatial scales by combining atmospheric …
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Studies of mercury in water, sediment, and fish in Mississippi: Concentrations, speciation, cycling, and isotopic composition
… goal of this project is to better understand the biogeochemical cycle of mercury (Hg) in Mississippi to aid those managing the resources and developing related policy. To that end, Hg levels were determined in a total of 202 fish from Enid, Sardis and Grenada Lakes; Enid and Grenada have fish …
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Studies on Selected Microbial Biotransformations of Arsenic Compounds
… poison and a cure in its past. It has a complex biogeochemical cycle in nature which was investigated. The major portion of this project looked primarily at arsenobetaine. Arsenobetaine is a benign form of arsenic that is ubiquitous throughout the marine environment representing the major form of …
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The chemistry of iron in hydrothermal plumes
… as a potential tool for<br/>tracing the biogeochemical cycle of Fe in the ocean. The forms of particulate Fe were<br/>elucidated using the particulate trace element data, enabling the isotope fractionation<br/>caused by Fe sulfide precipitation to be determined. A diagnostic isotope …
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The microbial communities and nutrient availability in pre and post harvested lodgepole pine stands of west-central Alberta
… within a forested system play a role in the biogeochemical cycle, not only within the forest but also within the global community. Soil microorganisms are a vital part of this cycle, as they sequester or make nutrients available for the development of the forest environment. When a …
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Terrestrial Si dynamics in the Arctic: a study on biotic and abiotic controls
… abundant element in the Earth’s crust and its biogeochemical cycle is linked with that of carbon. Further, silicon is a beneficial nutrient for plants in terrestrial ecosystems and a key nutrient for diatoms in aquatic ecosystems. During the last decade the important role of terrestrial …
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Microbial Oxidation of Arsenite in Anoxic Environments: Impacts on Arsenic Mobility
… bacteria and chlorate respiring bacteria in the biogeochemical cycle of arsenic. This study also investigated a arsenic potential bioremediation strategy based on injecting nitrate or chlorate into contaminated groundwater and surface water under anaerobic conditions.In this study, …
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The Diversity and Function of Bacteria Enriched from Gold Particles: Understanding Bacterial Contribution to Biogeochemical Cycling of Gold
… Collectively, these processes constitute the biogeochemical cycle of gold, which can be catalysed by bacteria, and have been interpreted from the characterisation of gold particles that have undergone (bio)transformation. Therefore, the primary focus of this study is to explore the diversity …
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Using Silicon Isotopes to Trace the Biogenic Silica in the Southern Ocean
… linked to the marine silicon (Si) and carbon (C) cycles. Diatoms are regarded as unicellular, eukaryotic organisms that form biogenic silica (bSi) frustules. The use of stable isotopes and physicochemical factors (temperature, light, and trace metal) provides a promising method for understanding …
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Using Silicon Isotopes to Trace the Biogenic Silica in the Southern Ocean
… linked to the marine silicon (Si) and carbon (C) cycles. Diatoms are regarded as unicellular, eukaryotic organisms that form biogenic silica (bSi) frustules. The use of stable isotopes and physicochemical factors (temperature, light, and trace metal) provides a promising method for understanding …
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An investigation of metal contaminants in sediments of Arctic Svalbard: Inferences for sources and transport pathways
… to improve the understanding of the complex Hg biogeochemical cycle.<br/>For the contaminant Cd, there has been unequivocal evidence from snow and ice records, indicating an increase in Cd flux from the mid 18th century to the mid 19th century, associated with anthropogenic influence. None of …
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Carbon and Nitrogen Dynamics of a Lagoon Salt Marsh in Davenport, California
… play a critical role in regulating the global biogeochemical cycle of carbon (C) and nitrogen (N). Wetlands are critical contributors to global climate change and atmospheric chemistry since they store as much as 33% of the world’s soil organic carbon (SOC), release more than 20% of the …
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Stable Carbon and Nitrogen Isotopes of Shell Bound organic Matter, Implications for Modern and Ancient Food Web Dynamics
… isotopes are an important tool for solving biogeochemical problems and have been increasingly applied in ecosystem studies because of their utility as source-to-sink tracers and for ecological information. Elements like C and N have more than one stable isotope, and their isotopic …