Using Time-Series Videos to Quantify Methane Bubbles Flux from Natural Cold Seeps in the South China Sea

Di, Pengfei; Dong, Feng; Tao, Jun; Chen, Duofu

doi:10.3390/min10030216

Cited by 19 publications

(11 citation statements)

References 65 publications

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“…The study of the release of methane from thermogenic and biogenic seeps in the world's oceans (and lakes) has expanded from simple recognition of the extent of the sources to efforts to characterize methane release mechanisms and quantify fluxes. These efforts include studies of: the exchange across the sediment water interface (Tryon and Brown, 2004;Kastner and MacDonald, 2006), bubble fluxes using bottom imaging (Leifer and MacDonald, 2003;Leifer, 2010;Thomanek et al, 2010;Römer et al, 2019;Di et al, 2020;Johansen et al, 2020), bubble fluxes using acoustic imaging (Weber et al, 2014), dissociation of hydrates (Lapham et al, 2010;Lapham et al, 2014), and inferred fluxes to the seafloor based on shallow thermal gradients (Smith et al, 2014). We now know that methane bubble release rates can vary on time scales of seconds, minutes, hours, and days (e.g., Greinert 2008;Leifer, 2019 (and references therein); Johansen et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Volumetric Mapping of Methane Concentrations at the Bush Hill Hydrocarbon Seep, Gulf of Mexico

2021

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The role of methane as a green-house gas is widely recognized and has sparked considerable efforts to quantify the contribution from natural methane sources including submarine seeps. A variety of techniques and approaches have been directed at quantifying methane fluxes from seeps from just below the sediment water interface all the way to the ocean atmosphere interface. However, there have been no systematic efforts to characterize the amount and distribution of dissolved methane around seeps. This is critical to understanding the fate of methane released from seeps and its role in the submarine environment. Here we summarize the findings of two field studies of the Bush Hill mud volcano (540 m water depth) located in the Gulf of Mexico. The studies were carried out using buoyancy driven gliders equipped with methane sensors for near real time in situ detection. One glider was equipped with an Acoustic Doppler Current Profiler (ADCP) for simultaneous measurement of currents and methane concentrations. Elevated methane concentrations in the water column were measured as far away as 2 km from the seep source and to a height of about 100 m above the seep. Maximum observed concentrations were ∼400 nM near the seep source and decreased away steadily in all directions from the source. Weak and variable currents result in nearly radially symmetric dispersal of methane from the source. The persistent presence of significant methane concentrations in the water column points to a persistent methane seepage at the seafloor, that has implications for helping stabilize exposed methane hydrates. Elevated methane concentrations in the water column, at considerable distances away from seeps potentially support a much larger methane-promoted biological system than is widely appreciated.

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Section: Introductionmentioning

confidence: 99%

Volumetric Mapping of Methane Concentrations at the Bush Hill Hydrocarbon Seep, Gulf of Mexico

2021

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“…These cold seeps might help our understanding of the dynamics and the environmental impacts of hydrocarbons [ 3 ]. Di et al determined size distribution, bubble release rate, and bubble diameters using a semiautomatic bubble-counting algorithm and observed that the Haima cold seeps in the South China Sea may be a source of methane for the ocean [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

A New Method for Training CycleGAN to Enhance Images of Cold Seeps in the Qiongdongnan Sea

Yang

Gong

et al. 2023

Sensors

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Clear underwater images can help researchers detect cold seeps, gas hydrates, and biological resources. However, the quality of these images suffers from nonuniform lighting, a limited range of visibility, and unwanted signals. CycleGAN has been broadly studied in regard to underwater image enhancement, but it is difficult to apply the model for the further detection of Haima cold seeps in the South China Sea because the model can be difficult to train if the dataset used is not appropriate. In this article, we devise a new method of building a dataset using MSRCR and choose the best images based on the widely used UIQM scheme to build the dataset. The experimental results show that a good CycleGAN could be trained with the dataset using the proposed method. The model has good potential for applications in detecting the Haima cold seeps and can be applied to other cold seeps, such as the cold seeps in the North Sea. We conclude that the method used for building the dataset can be applied to train CycleGAN when enhancing images from cold seeps.

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“…Nevertheless, a single seepage point just releases 4.8 bubbles per second, each bubble is about 3.25 mm in diameter, and the corresponding gas flux is only 6.75 mL/min. 22 Such a low gas flow rate cannot meet the requirement for a BFEH system to work. To enhance the gas-intake rate of a BFEH system, it is possible to enable an accumulation of low-gas-flux bubbles collected over a long period to pass through it in a short time period.…”

Section: ■ Introductionmentioning

confidence: 99%

Passive Automatic Switch Relying on Laplace Pressure for Efficient Underwater Low-Gas-Flux Bubble Energy Harvesting

Wen

et al. 2023

Langmuir

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The buoyancy potential energy contained in bubbles released by subsea geological and biological activities represents a possible in situ energy source for underwater sensing and detection equipment. However, the low gas flux of the bubble seepages that exist widely on the seabed introduces severe challenges. Herein, a passive automatic switch relying on Laplace pressure is proposed for efficient energy harvesting from low-gas-flux bubbles. This switch has no moving mechanical parts; it uses the Laplace-pressure difference across a curved gas−liquid interface in a biconical channel as an invisible "microvalve". If there is mechanical equilibrium between the Laplacepressure difference and the liquid-pressure difference, the microvalve will remain closed and prevent the release of bubbles as they continue to accumulate. After the accumulated gas reaches a threshold value, the microvalve will open automatically, and the gas will be released rapidly, relying on the positive feedback of interface mechanics. Using this device, the gas buoyancy potential energy entering the energy harvesting system per unit time can be increased by a factor of more than 30. Compared with a traditional bubble energy harvesting system without a switch, this system achieves a 19.55-fold increase in output power and a 5.16-fold enhancement in electrical energy production. The potential energy of ultralow flow rate bubbles (as low as 3.97 mL/min) is effectively collected. This work provides a new design philosophy for passive automatic-switching control of gas−liquid two-phase fluids, presenting an effective approach for harvesting of buoyancy potential energy from low-gas-flux bubble seepages. This opens a promising avenue for in situ energy supply for subsea scientific observation networks.

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Using Time-Series Videos to Quantify Methane Bubbles Flux from Natural Cold Seeps in the South China Sea

Cited by 19 publications

References 65 publications

Volumetric Mapping of Methane Concentrations at the Bush Hill Hydrocarbon Seep, Gulf of Mexico

Volumetric Mapping of Methane Concentrations at the Bush Hill Hydrocarbon Seep, Gulf of Mexico

A New Method for Training CycleGAN to Enhance Images of Cold Seeps in the Qiongdongnan Sea

Passive Automatic Switch Relying on Laplace Pressure for Efficient Underwater Low-Gas-Flux Bubble Energy Harvesting

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