Direct Observation of Wind‐Induced Pressure‐Pumping on Gas Transport in Soil. Issue 4 (20th July 2017)

• Record Type: Journal Article
• Authors: Laemmel, T.; Mohr, M.; Schack-Kirchner, H.; Schindler, D.; Maier, M.
• Is Part Of: Soil Science Society of America Journal. Volume 81:Issue 4(2017)
• Page Start: 770
• Page End: 774
• Publication Date: 2017-07-20
• Subjects: Soils -- United States -- Periodicals; Soil science -- Periodicals; Periodicals; 631.4973
• DOI: 10.2136/sssaj2017.01.0034n
• Languages: English
• ISSNs: 0361-5995

Abstract

Abstract : 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.