Sökning: "δ13C"
Visar resultat 11 - 15 av 36 avhandlingar innehållade ordet δ13C.
11. Holocene climate and environmental change in high latitudes as recorded by stable isotopes in peat deposits
Sammanfattning : In this thesis, stable carbon and oxygen isotopes in α-cellulose isolated from Sphagnum fuscum moss remains were used as climate proxies. The main focus was to implement the methods in records from high latitude peatlands in the Northern Hemisphere (west-central Canada and north-eastern European Russia), reconstruct palaeoclimate of the studied regions during the Holocene, and evaluate the compatibility of results with other proxy records, especially tree-ring isotope time-series. LÄS MER
12. Climate in the eastern Mediterranean during the Holocene and beyond – A Peloponnesian perspective
Sammanfattning : This thesis contributes increased knowledge about climate variability during the late Quaternary in the eastern Mediterranean. Results from a paleoclimate review reveal that regional wetter conditions from 6000 to 5400 years BP were replaced by a less wet period from 5400 to 4600 years BP and to fully arid conditions around 4600 years BP. LÄS MER
13. Origin of organic compounds in fluids from ultramafic-hosted hydrothermal vents of the Mid-Atlantic Ridge
Sammanfattning : Natural gas, primarily methane (CH4), is produced in substantial amounts in ultramafic-hosted hydrothermal systems. These systems could also generate oil (heavier hydrocarbons) and the first building blocks of life (prebiotic molecules). In the presence of iron bearing minerals, serpentinisation reactions generate H2. LÄS MER
14. Towards understanding stable isotope signatures in stressed systems
Sammanfattning : Stable isotope analysis (SIA) is a valuable tool in ecotoxicology because δ13C and δ15N may provide insights into the trophic transfer of contaminants in a food web. The relationship between a species’ trophic position (TP, determined from δ15N) and internal concentration of biomagnifying contaminants can be established and used for regulatory purposes. LÄS MER
15. Studies on Tropical Palaeo-variation in Climate and Cosmic Ray Influx : Geochemical data from stalagmites collected in Tanzania and northern South Africa
Sammanfattning : The main aims of this project were to contribute to the knowledge about tropical climate variations, and to investigate the possibilities of obtaining cosmic ray influx data from stalagmites.Stalagmites from Tanzania and northern South Africa were palaeoclimatologically analysed. LÄS MER
