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Direct Observation of Wind‐Induced Pressure‐Pumping on Gas Transport in Soil
Author(s) -
Laemmel T.,
Mohr M.,
Schack-Kirchner H.,
Schindler D.,
Maier M.
Publication year - 2017
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2017.01.0034n
Subject(s) - environmental science , soil gas , thermal diffusivity , topsoil , flux (metallurgy) , diffusion , atmospheric sciences , wind speed , atmospheric pressure , pressure gradient , soil science , soil water , meteorology , chemistry , geology , physics , thermodynamics , organic chemistry
Core Ideas We directly observed the effect of wind‐induced pressure‐pumping on gas transport in soil. Mean above‐canopy wind speeds >3 m s −1 increase the soil gas transport rate by about 10%. We generally recommend considering the pressure‐pumping effect in gas flux measurements. Soil gas transport is commonly assumed to be governed by molecular diffusion. However, nondiffusive transport processes such as wind‐induced pressure‐pumping can significantly enhance soil gas transport during periods of high wind speed. During a field campaign at a forest site, we combined methods to measure soil gas transport, air pressure, and airflow characteristics. We directly observed the enhancement of gas transport due to wind‐induced air pressure fluctuations during two periods when mean above‐canopy wind speeds exceeded 3 m s –^91 . Specifically, we measured an increase of the topsoil gas diffusivity of about 10%. The wind‐induced air pressure fluctuations, which were responsible for pressure‐pumping, had frequencies of 0.02 Hz and amplitudes up to 5 Pa. Overall, our results show that wind‐induced pressure‐pumping can substantially increase the commonly diffusion‐limited transport rate of soil gases. We therefore recommend considering this process in gas flux measurements in the field and in the laboratory.