Bubble transport in natural waters
Bubble transport is the most efficient mechanism of gases in natural stratified waters. Research at Eawag has focused on two aspects of bubble transport:
- input of oxygen into the hypolimnion of lakes using artificial bubble plumes (Hypolimnetic Oxygenation),
- methane transport in water bodies due to bubble formation at the sediment.
Hypolimnetic Oxygenation
Studies were performed on artificial plumes operated in Lake Hallwil,
Switzerland. The system of 6 circular bubble plume diffusers was
installed to enhance the deep water oxygen content.
Bubble plume modeling is performed to optimize operation:
- Comparison of field data with model results
- Full scale study to determine effects and efficiency of the oxygenation system.
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Hypolimnetic oxygenation: High resolution temperature (oC) slice through a bubble plume in Lake Hallwil, Switzerland.
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Funding
- U.S. National Science Foundation, Eawag, Kanton Aargau
Collaboration
- Arno Stöckli (Kanton Aargau), John Little (Virginia Tech)
Hydroacoustic sensing and modeling of methane bubbles in natural waters
Methane from sediments can reach the atmosphere directly via bubbles and contribute to global warming. Methane gas bubble dissolution is quantified using a combination of modeling and acoustic observations of rising bubbles to determine the fraction of the methane that will reach the atmosphere.
Our studies suggest that a small amount of methane reaches the surface from very shallow water areas (< 100 m). The ocean is a effective barrier against the transfer of bubble methane to the atmosphere, although substantial amounts of methane may reach the surface in shallow lakes and reservoirs.
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Hydroacoustic identification of bubble flares from mud volcanoes in the Black Sea deep waters. |