1D Air Pressure Fluctuations Cannot Fully Explain the Natural Pressure‐Pumping Effect on Soil Gas Transport
| Autor: | Manuel Mohr, Dirk Schindler, Helmer Schack-Kirchner, Thomas Laemmel, Martin Maier |
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| Rok vydání: | 2019 |
| Předmět: |
Molecular diffusion
Field (physics) Atmospheric pressure Soil gas Soil Science 04 agricultural and veterinary sciences Mechanics 010501 environmental sciences Thermal diffusivity 01 natural sciences Bottleneck Wind speed Amplitude 040103 agronomy & agriculture 0401 agriculture forestry and fisheries Environmental science 0105 earth and related environmental sciences |
| Zdroj: | Soil Science Society of America Journal. 83:1044-1053 |
| ISSN: | 1435-0661 0361-5995 |
| Popis: | While gas transport in soil is commonly assumed to be driven by molecular diffusion, pressure-pumping due to small air pressure fluctuations was found to enhance the gas transport rate during periods of high wind speed. A possible explanation is related to the vertical oscillating movement of gas in the air-filled pore space due to these air pressure fluctuations. Exposing granular and artificial samples to vertical air pressure fluctuations with realistic amplitudes and frequencies in the laboratory, we show that they indeed can increase the effective gas diffusivity through the samples. The enhancement of gas diffusivity was higher for samples characterizing by a low bottleneck area and a low bottleneck density and it was lower for samples with small bottleneck length. However, there was a significant discrepancy between the gas transport enhancement observed in the field and under laboratory conditions by comparable soil air movement due to oscillating flow. The exclusive consideration of vertical air pressure fluctuations in the laboratory seems insufficient to explain effects of the pressure-pumping in the field on soil gas transport rates. |
| Databáze: | OpenAIRE |
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