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 96 for “"lake sediments"”.
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Chemical Survey of Selected South Dakota Lake Sediments
… and organic nitrogen were measured in bottom sediments of 16 lakes and ponds in northeast South Dakota. These lakes were glaciated, relatively shallow, and productive. Ranges of the surface sediments were: available phosphorus, 2 to 42 ppm; organic carbon, 0.94 to 5.34 percent; and organic …
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Numerical modeling of methane venting from lake sediments
The dynamics of methane transport in lake sediments control the release of methane into the water column above, and the portion that reaches the atmosphere may contribute significantly to the greenhouse effect. The observed dynamics are poorly understood. In particular, variations in the …
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Spatiotemporal variability of methane ebullition from lake sediments
… spatial structure of methane venting from soft sediments in a eutrophic lake over a range of spatial scales, from 1 cm to 20 m, and using a combination of field observations and laboratory experiments. Field-scale measurements of ebullition were acquired at the bottom of Upper Mystic Lake, MA, …
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Microbiological influences on phosphorus release from aerobic lake sediments
The role of sediments in regulating nutrient availability in lakes and reservoirs has been the subject of many recent studies. Classical theories concerning the regulation of phosphorus release from sediments by oxidation-reduction potential neglect the potential of microorganisms to transfer large …
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Setting the Holocene clock using varved lake sediments in Sweden
… to study annually laminated (varved) Holocene lake sediment in Sweden, their formation and their potential as chronological and palaeoecological archives. Five lakes with continuous Holocene varved lake sediment sequences in northern (Västerbotten) and west central Sweden (Värmland) were …
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A study of nutrient distributions and productivity potential in lake sediments
… the sediment in the upper reaches of Claytor Lake. The lake is a manmade impoundment on the New River near Radford, Virginia. Eleven core samples, varying in length from 66 cm. to 141 cm, were taken from the lake. The concentration of various water quality parameters were determined for …
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Hydro- and biogeochemical investigations of lake sediments in the Kenyan Rift Valley
Die Seen im kenianischen Riftsystem bieten die einmalige Gelegenheit eine große Bandbreite an hydrochemischen Umweltbedingungen zu studieren, die von Süßwasserseen bis hin zu hochsalinen und alkalinen Seen reichen. Da wenig über die hydro- und biogeochemischen Bedingungen in den darunterliegenden …
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Phylogenetic and physiological characterization of deep-biosphere microorganisms in El’gygytgyn Crater Lake sediments
… microbial communities in the deep subsurface of lake systems and their potentials to adapt to changing environmental conditions is still fragmentary. This doctoral thesis aims to build up a unique data basis for providing the first detailed high-throughput characterization of the deep biosphere …
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Lake sediments as climate and tectonic archives in the Indian summer monsoon domain
… valley and one in the core monsoon zone (Lonar lake) in central India); (iii) undertaken a regional overview to generate “snapshots” of selected time slices; and (iv) interpreted the spatial precipitation anomalies in terms of those caused by modern teleconnections. This approach must be …
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Distribution and chronology of ²³⁹ ²⁴⁰Pu and ¹³⁷Cs in Colorado Front Range lake sediments
Includes bibliographical references.
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Holocene climate and environmental variability in NE Germany inferred from annually laminated lake sediments
… in NE Germany based on annually laminated lake sediments. The work contributes to the ICLEA project (Integrated CLimate and Landscape Evolution Analyses). ICLEA intends to compare multiple high-resolution proxy records with independent chronologies from the N central European lowlands, in …
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Reconstructing Australia’s late Quaternary climate from the geochemistry of lake sediments and snail shells
… measurements of a sedimentary sequence from Lake Surprise in south-eastern Australia (Chapter 3). The regional significance of this record is assessed using a Monte Carlo Empirical Orthogonal Function approach. 2) The high-resolution record is supported by three discrete quantitative …
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Assembly and functioning of microbial communities along terrestrial resource gradients in boreal lake sediments
… resources is especially important in boreal lakes that are largely nutrient-poor and thus more responsive to these additions. Yet the mechanisms underlying initial processing of terrestrial resources by microbial communities at the base of lake food webs remain poorly understood. With this in …
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Fate of polycyclic aromatic hydrocarbons associated with coal-tar pitch, asphalt, charcoal, and soot in urban lake sediments
… polycyclic aromatic hydrocarbons (PAHs) in urban lake sediments have increased significantly over the past several decades. Increased PAH loadings have been correlated with urbanization, and carbonaceous materials (CMs) such as coal tar and asphalt sealcoat and soot. PAH concentrations in urban …
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Palaeoenvironmental reconstruction in South Africa's year-round rainfall zone using multiproxy geochemical analyses on lake sediments from Swartvlei
Coastal lakes in the south coast of South Africa contain sediments with good records of palaeoenvironmental changes. Swartvlei is the largest of the lakes in the Wilderness Embayment and is connected to the Indian Ocean via an estuary. The lake is believed to have been formed during sea-level …
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Investigations on rainfall variability during the late Quaternary based on geochemical analyses of lake sediments from tropical and subtropical southern Africa
This thesis presents investigations on sediments from two African lakes which have been recording changes in their surrounding environmental and climate conditions since more than 200,000 years. Focus of this work is the time of the last Glacial and the Holocene (the last ~100,000 years before …
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The Role of Carbonaceous Materials in Pavement Dust, Soils, and Lake Sediments on the Fate of Organic Pollutants in Small Urban Watersheds
Field samples were fractionated into light (LFr), heavy (HFr), and condensed CMs (CCMs) fractions with sequential physical and chemical treatment. These fractions and bulk samples were characterized with elemental analysis, Fourier transform infrared spectroscopy, specific surface area measurement, …
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Lateglacial to Holocene climatic and environmental changes in Europe : multi-proxy studies on lake sediments along a transect from northern Italy to northeastern Poland
Sediment records of three European lakes were investigated in order to reconstruct the regional climate development during the Lateglacial and Holocene, to investigate the response of local ecosystems to climatic fluctuations and human impact and to relate regional peculiarities of past climate …
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