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Effects of atmospheric pressures on gas transport in the vadose zone
Author(s) -
Massmann Joel,
Farrier Daniel F.
Publication year - 1992
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/91wr02766
Subject(s) - vadose zone , advection , infiltration (hvac) , pressure gradient , environmental science , atmospheric pressure , geology , diffusion , porous medium , permeability (electromagnetism) , atmospheric sciences , hydrology (agriculture) , soil science , soil water , meteorology , porosity , geotechnical engineering , chemistry , thermodynamics , biochemistry , oceanography , physics , membrane
Temporal variations in barometric pressure due to weather patterns may induce air intrusion into the subsurface. This air intrusion can affect monitoring activities aimed at characterizing the composition and movement of gases in the vadose zone. Expressions are presented to estimate gas fluxes due to the combined effects of Knudsen diffusion, multicomponent molecular diffusion, and viscous flow. These expressions are used to evaluate the validity of the single‐component advection‐dispersion equation for simulating gas transport in the presence of atmospheric pressure variations. The single‐component equation provides reasonable results when used to simulate transport in media with relatively high gas permeability. Computer simulations of vertical transport at sites with homogeneous soils indicate that “fresh” air can migrate several meters into the subsurface during a typical barometric pressure cycle. Horizontal pressure gradients can develop at sites with near‐surface heterogeneities. These gradients may cause fresh air to intrude meters or tens of meters into the vadose zone during a storm event.