Modeling Gas Flow Velocities in Soils Induced by Variations in Surface Pressure, Heat, and Moisture Dynamics

Abstract

For nearly the past 120 years variations in atmospheric pressure and wind at the Earth's (solid) surface have been understood as a key mechanism responsible for air movement in and out of soils (Buckingham, 1904) and snowpacks (Dubrovin, 1961). For nearly as long variations of these atmospheric variables have formed the basis for modeling the induced advective velocities within soils (Buckingham, 1904) and snowpacks (Clarke et al., 1987). This phenomenon is often identified as "pressure pumping," "barometric pumping," or "windpumping." (Note: The term pressure pumping will be used exclusively in the present study and that by soils we mean a porous media free of cracks or macropores.) Thus this study focuses on advective currents in soils that are driven by periodic (mechanically forced or thermally induced) pressure variations that are distinct from density or thermally driven (i.e., overturning) convective currents that often dominate fractured or high permeability soils (e.g.

Small lateral air pressure gradients generated by a large chamber system have a strong effect on CO2 transport in soil

“…When considering bulk flow, rising concentrations can also result from the vertical transport of gas from depths with higher CO 2 concentrations. Therefore, when nondiffusive transport occurs, more complex numerical flux estimation models must be used, like the model presented by Massman and Frank (2022). The presented chamber system could simulate pressure fields in a realistic range.…”