Journal Article

Gas Diffusivity in Undisturbed Volcanic Ash Soils

Komatsu, Toshiko, Olesen, Torben, Rolston, Dennis E., Yoshikawa, Seiko, Moldrup, Per

2003

Overview

Soil‐water‐characteristic‐dependent (SWC‐dependent) models to predict the gas diffusion coefficient, D P , in undisturbed soil have only been tested within limited ranges of pore‐size distribution and total porosity. Andisols (volcanic ash soils) exhibit unusually high porosities and water retention properties. The Campbell SWC model and two Campbell SWC‐based models for predicting D P in undisturbed soil were tested against SWC and D P data for 18 Andisols and four Gray‐lowland (paddy field) soils from Japan. The Campbell model accurately described SWC data for all 22 soils within the matric potential range from ≈ −10 to −15000 cm H 2 O. The SWC‐dependent Buckingham‐Burdine‐Campbell (BBC) gas diffusivity model predicted D P data well within the same matric potential range for the 18 Andisols. The BBC model showed a minor but systematic underprediction of D P for three out of the four Gray‐lowland soils, likely due to a blocky soil structure with internal fissures. A recent D P model that also takes into account macroporosity performed nearly as well as the BBC model. However, D P in the macropore region (air‐filled pores >30 μm) was consistently underpredicted, likely due to high continuity of the macropore system in both Andisols and Gray‐lowland soils. In agreement with previous model tests for 21 European soils (representing lower porosities and water retention properties), both SWC‐dependent D P models gave better predictions for the 22 Japanese soils than soil‐type independent models. Combining D P and SWC data, a so‐called gas diffusion fingerprint (GDF) plot to describe soil aeration potential is proposed.

• Publisher: Soil Science Society of America,American Society of Agronomy
• Subject: aeration / Andisols / Biological and medical sciences / Diffusion coefficient / diffusivity / Fundamental and applied biological sciences. Psychology / Gases / Japan / macropores / mathematical models / Moisture content / paddy soils / Porosity / prediction / Prediction models / Retention / Soil aeration / Soil structure / Soil testing / Soil water / Soils / volcanic ash soils / Volcanic soils / Volcanoes / Water