Methane Bubble Ascent within Fine-Grained Cohesive Aquatic Sediments: Dynamics and Controlling Factors

Area of Science:

• Environmental Science
• Geochemistry
• Fluid Dynamics

Background:

• Methane (CH4) is a potent greenhouse gas.
• Release of CH4 from aquatic sediments is a significant environmental concern.
• Understanding bubble dynamics is crucial for predicting methane emissions.

Purpose of the Study:

• To investigate the ascent of methane bubbles in muddy aquatic sediment.
• To model bubble behavior under varying overburden loads.
• To determine factors controlling methane bubble release.

Main Methods:

• A coupled macroscopic single-bubble mechanical/reaction-transport numerical model was employed.
• Simulated two distinct bubble ascent scenarios: stable and dynamic.
• Analyzed the influence of effective overburden loads (≤11 kPa) on bubble trajectory.

Main Results:

• Stable ascent followed by dynamic ascent occurred at low overburden loads, leading to bubble release.
• High overburden loads resulted in stable ascent, with bubbles stopping at the gas horizon.
• Bubble migration is primarily governed by inner bubble pressure and solute exchange.

Conclusions:

• Bubble ascent dynamics significantly impact methane release from sediments.
• Overburden load is a key factor determining whether methane bubbles escape or are trapped.
• This research aids in estimating atmospheric methane emissions and sediment property changes.