Schlüsselwörter
(Englisch)
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Greenhouse gas; long-term monitoring; methane emissions; noble gases
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Forschungsprogramme
(Englisch)
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COST-Action ES0902 - Permafrost and gas hydrate related methane release in the Arctic and impact on climate change: European cooperation for long-term monitoring: PERGAMON
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Kurzbeschreibung
(Englisch)
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This project aims towards the mechanistic understanding of methane distribution in sediment pore water and its transport from the sediments into the overlying water column. For this we aim to investigate the sediments of Lake Rotsee (Switzer-land) and the Black Sea, which are known to contain high concentrations of methane. We aim to investigate the dynamics and origin of methane-rich fluids in these sediments using noble-gas isotopes as proxies. Furthermore, we aim to consoli-date and further expand the use of noble-gas geochemistry as a widely applicable tool to study the transport of fluids and solutes in unconsolidated sediments and to extend the area of application of noble-gas geochemistry in aquatic systems and environmental sciences. This project is closely linked to the COST Action Pergamon that is investigating gas hydrate related methane release in the Arctic realm and to the EU project 'Hypox' which monitors global change driven oxygen depletion in aquatic systems.
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Partner und Internationale Organisationen
(Englisch)
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BE, BG, CH, DE, DK, EL, ES, FI, FR, I, IT, NL, NO, PL, PT, SE, UK
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Abstract
(Englisch)
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Over the years, methane profiles have been measured in the sediments of numerous lakes across several projects, including the COST Action project ES0902. The source of the measured methane was in-situ microbial production or release from gas hydrates. However, the mechanism by which the methane reaches the surface of the sediments and its transport through the water column is not well understood, which is a very unsatisfactory situation. During the last few years we have developed experimental techniques to sample and analyze dissolved noble gases and methane in the pore water of unconsolidated sediments. Preliminary applications of these methods indicate that dissolved noble gases in sediment pore water are promising proxies for reconstructing (palaeo)environmental conditions in lakes and in the ocean, for analyzing the transport of solutes within the sediment column, and for studying gas release into the overlying water body and into the atmosphere. From a conceptual point of view, the key conclusion of all these studies is that in some sediments the diffusivity of noble gases in the sediment pore water is similar to their molecular diffusivity in bulk water. In other sediments, however, noble gases are trapped in the sediment pore space and diffusion is therefore strongly suppressed. This trapping results in a stratigraphy-controlled noble-gas and methane record in the sediment pore space, which allows a time-scale to be associated with the noble-gas record in the pore water. However, a mechanistic understanding of the suppression of diffusion is required to establish the conceptual basis needed for future applications of noble gases as proxies for past environmental conditions and for the physical transport of pore fluids. To better understand the above-mentioned processes, we investigated the sediments of Lake Rot and the Black Sea, which are known to contain high concentrations of methane. We studied the dynamics and origin of methane-rich fluids in these sediments using noble-gas isotopes as proxies. Furthermore, we will be able to consolidate and further expand the use of noble-gas geochemistry as a widely applicable tool to study the transport of fluids and solutes in unconsolidated sediments and to extend the area of application of noble-gas geochemistry in environmental sciences.
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Datenbankreferenzen
(Englisch)
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Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. +41 31 322 74 82 Swiss Project-Number: C11.0029
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