Sökning: "geokemi"
Visar resultat 11 - 15 av 285 avhandlingar innehållade ordet geokemi.
11. Export and sources of organic carbon in the Lena River basin, Northeastern Siberia
Sammanfattning : Permafrost areas are considered to be one of the largest terrestrial storages of carbon. In a warming climate these areas are expected to experience changes in carbon transport to rivers and the oceans due to permafrost thawing, which could enhance erosion, change water flow pathways and increase greenhouse gas emissions. LÄS MER
12. Microbially mediated formation of birnessite-type manganese oxides and subsequent incorporation of rare earth elements, Ytterby mine, Sweden
Sammanfattning : Microbes exert extensive control on redox element cycles. They participate directly orindirectly in the concentration and fractionation of elements by influencing the partitioningbetween soluble and insoluble species. LÄS MER
13. Isotope-based reconstruction of the biogeochemical Si cycle : Implications for climate change and human perturbation
Sammanfattning : The global silicon (Si) cycle is of fundamental importance for the global carbon cycle. Diatom growth in the oceans is a major sequestration pathway for carbon on a global scale (often referred to as the biological pump). LÄS MER
14. Late-orogenic, ductile shear zones and protolith ages in the Svecofennian domain, central Sweden
Sammanfattning : The timing of deformation along ductile shear zones in the Svecofennian Domain in central Sweden has generally been constrained by their relationship to magmatic and metamorphic events of known age. A better resolution for the timing of the deformation can be obtained by direct, radiometric dating of minerals which are constituents of the shear fabric. LÄS MER
15. Hydrothermal alteration of organic matter at spreading centers
Sammanfattning : Alteration of organic matter, mainly amino acids, at sub-seafloor hydrothermal conditions has been investigated by performing laboratory experiments and by studying deep-sea sediments from hydrothermally active areas on the northern Juan de Fuca Ridge, northeast Pacific Ocean.Quaternary sediments from Middle Valley and the eastern flank of the Juan de Fuca Ridge recovered during the Ocean Drilling Program Legs 139 and 168 have been analyzed for total hydrolyzable amino acid concentrations, individual amino acid abundances and stereochemistry in order to evaluate the effects of hydrothermal stress on the decomposition of sedimentary amino acids. LÄS MER