Inhaltszusammenfassung

Ebullition is an important pathway for methane emission from inland waters. However, the mechanisms controlling methane bubble formation and release in aquatic sediments remain unclear. A laboratory incubation experiment was conducted to investigate the dynamics of methane bubble formation, storage and release in response to hydrostatic head drops in three different types of natural sediment. Homogenized clayey, silty and sandy sediments (initially quasi-uniform th...Ebullition is an important pathway for methane emission from inland waters. However, the mechanisms controlling methane bubble formation and release in aquatic sediments remain unclear. A laboratory incubation experiment was conducted to investigate the dynamics of methane bubble formation, storage and release in response to hydrostatic head drops in three different types of natural sediment. Homogenized clayey, silty and sandy sediments (initially quasi-uniform through the depth of the columns) were incubated in chambers for three weeks. We observed three distinct stages of methane bubble formation and release: Stage I formation of micro bubbles, displacing mobile water from sediment pores with negligible ebullition; Stage II formation of large bubbles, displacing the surrounding sediment with concurrent increasing iin ebullition; Stage III formation of conduits, with relatively steady ebullition. The maximum depth-averaged volumetric gas content at steady state varied from 19silty and 13strong vertical stratification in terms of both bubble number and size with depth. Most of the free gas was stored in an upper layer, whose thickness varied with sediment grain size. The magnitude of individual ebullition episodes was linearly correlated to hydrostatic head drop and decreased from clayey to sandy to silty sediment. These findings combined with a hydrodynamic model capable of determining dominant sediment type and depositional zones could help resolve spatial heterogeneities in methane ebullition at medium to larger scales in inland waters.» weiterlesen» einklappen

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