Influence of Pore Gas on Ponded Infiltration into Soil Columns: Fid-Bau Portal

Influence of Pore Gas on Ponded Infiltration into Soil Columns

Prunty, Lyle / Bell, Joel

Gas present in soil pores prior to an infiltration event can substantially influence the process. The objective of this study is to compare infiltration rates under a range of pore gas conditions. Ponded infiltration with falling-head conditions was measured for two soils. Prior to infiltration the pore space of the soil was flooded with one of several gases at atmospheric pressure or a vacuum was drawn. Experiments were conducted on laboratory infiltration columns designed and fabricated to apply >200 mm of water head nearly instantaneously and with negligible turbulence. The highly soluble gases including CO₂ and C₂H₂ resulted in infiltration rates 2 and 3 times faster than with air and gases similar in solubility to air for the Hecla loamy fine-sand and Glyndon loam soils. A vacuum in the pore space prior to infiltration also resulted in an increase in infiltration rate. With vacuum there was a tendency for spontaneous boiling at the interface of the ponded water and soil. Encapsulated pockets primarily consisting of water vapor may form in highly reduced pressure (vacuum) systems and limit infiltration rates compared to CO₂-saturated systems. By doing experiments with a wide range of gases to determine their influence on infiltration, knowledge about infiltration may be advanced to a broader basis.