Sökning: "lake sediment"

Visar resultat 1 - 5 av 162 avhandlingar innehållade orden lake sediment.

  1. 1. Lake sediment as environmental archive : natural and anthropogenic influence on the chronology of trace elements

    Författare :Evastina Grahn; Stefan Karlsson; Anders Düker; Bo Bergbäck; Örebro universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; lake sediment; environmental pollution; trace elements; chronology; diagenesis; Ag; Be; Ga; In; Pb; Sb; Tl; Environmental chemistry; Miljökemi; Enviromental Science; Miljövetenskap;

    Sammanfattning : The focus of this thesis is the historical pollution of some seldom-monitored trace elements (SMTEs; Ag, Be, Ga, In, Sb and Tl) that have been involuntarily released for several thousands of years but whose usage have increased during the industrial era. Sediment cores from four rural lakes in a south to north transect in central Sweden, and two urban lakes have been used as environmental archives for chronological studies. LÄS MER

  3. 2. Diatom-rich sediment formation in lakes

    Författare :Petra Zahajská; Kvartärgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Silicon; silica; diatom; biogenic silica; lake; sediment; stable Si isotopes; Ge Si; Yellowstone; Northern Sweden;

    Sammanfattning : Unicellular photosynthetic golden algae called diatoms are one of the most abundant silicifying organisms. Diatoms take up silicon and build their frustules, in the form of biogenic silica (BSi), which have high preservation potential, and thus are found in sediments. LÄS MER

  4. 3. The role of benthic macrofauna in nitrogen cycling in eutrophic lake sediment

    Författare :Jonas Martin Svensson; Biologiska institutionen; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; nitrogen retention; nitrous oxide; oligochaetes; chironomids; mineralisation; nitrification; denitrification; eutrophic; sediment; lake; Macrofauna; nitrogen cycling; fish reduction.; Ecology; Ekologi;

    Sammanfattning : This thesis concerns the role of sediment-living macrobenthos in the cycling of nitrogen species and nitrogen transformation in eutrophic freshwater sediments. In my thesis I have, employing 15N-isotope techniques in laboratory experiments, shown the importance of infaunal chironomid larvae and oligochaetes on denitrification in eutrophic lake sediments. LÄS MER

  5. 4. Infrared spectroscopy as a tool to reconstruct past lake-ecosystem changes : Method development and application in lake-sediment studies

    Författare :Carsten Meyer-Jacob; Richard Bindler; Hendrik Vogel; Jan Karlsson; John F. Boyle; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Fourier transform infrared spectroscopy; visible-near infrared spectroscopy; PLS regression; biogenic silica; climate change; carbon cycling; lake-water quality; geochemistry; paleolimnology; Holocene; Lake El’gygytgyn; Torneträsk;

    Sammanfattning : Natural archives such as lake sediments allow us to assess contemporary ecosystem responses to climate and environmental changes in a long-term context beyond the few decades to at most few centuries covered by monitoring or historical data. To achieve a comprehensive view of the changes preserved in sediment records, multi-proxy studies – ideally in high resolution – are necessary. LÄS MER

  7. 5. Molecular analysis of lake-sediment organic matter : long-term dynamics and environmental implications in boreal lakes

    Författare :Sofia Ninnes; Richard Bindler; Xiao-Ru Wang; Christian Bigler; Hendrik Vogel; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Lake sediment; Holocene; organic matter; Pyrolysis-GC MS; mid-infrared spectroscopy; boreal;

    Sammanfattning : Lake sediment organic matter is material composed of residues from plants, algae, animals, fungi and bacteria. Its molecular composition is dependent on the sources as well as secondary biotic and abiotic transformations, which combined generates a highly complex matrix. LÄS MER