Simulating diffusion in a Boolean model of soil pores

Summary The diffusion of gas through a model of the structure of soil pores was simulated on a computer. This was done to test the model's usefulness for studying diffusion in real soil and to obtain insights into how soil pore geometry affects diffusion. A model of randomly-placed overlapping spheres was used to represent the soil solids, the pores being what remains. Various simulated porosities and average sphere radii produced pore networks which resembled those in real soil aggregates. Our diffusion simulations gave three results: steady-state flux, time delay and rate of increase of flux. The porosity and sphere size were varied to investigate their effects on these diffusion properties. Results were comparable with those from experimental work. Further analysis allowed us to express the geometry of pore simulations in terms of average pore path length and connectivity. Evidence of non-Fickian behaviour was obtained, particularly in the early stages of the simulated diffusion.

[1]  B. Ball,et al.  A functional model of soil porosity used to interpret measurements of gas diffusion , 1994 .

[2]  John W. Crawford,et al.  Quantification of fungal morphology, gaseous transport and microbial dynamics in soil: an integrated framework utilising fractal geometry , 1993 .

[3]  C. Glasbey,et al.  Image analysis and three‐dimensional modelling of pores in soil aggregates , 1991 .

[4]  F. Bartoli,et al.  Structure and self‐similarity in silty and sandy soils: the fractal approach , 1991 .

[5]  John W. Crawford,et al.  The fractal structure of soil aggregates: its measurement and interpretation , 1991 .

[6]  A. Rasmuson,et al.  A Comparison of Gas Diffusivity Models for Unsaturated Porous Media , 1988 .

[7]  M. F. O'sullivan,et al.  Gas diffusion, fluid flow and derived pore continuity indices in relation to vehicle traffic and tillage , 1988 .

[8]  J. Bouma,et al.  VARIABILITY OF SATURATED HYDRAULIC CONDUCTIVITY IN A GLOSSAQUIC HAPLUDALF WITH MACROPORES , 1988 .

[9]  S. Havlin,et al.  Diffusion in disordered media , 1991 .

[10]  M. Bradbury,et al.  The effect of dead-end porosity on rock-matrix diffusion , 1985 .

[11]  J. Letey,et al.  Measurement of gas diffusion coefficient under relatively low air-filled porosity [Aeration, soil diffusivity, gas movement]. , 1984 .

[12]  J. D. Jabro,et al.  Gaseous diffusion equations for porous materials , 1982 .

[13]  B. C. Ball,et al.  MODELLING OF SOIL PORES AS TUBES USING GAS PERMEABILITIES, GAS DIFFUSIVITIES AND WATER RELEASE , 1981 .

[14]  J. R. Burford,et al.  A LABORATORY METHOD TO MEASURE GAS DIFFUSION AND FLOW IN SOIL AND OTHER POROUS MATERIALS , 1981 .

[15]  J. Currie,et al.  Gaseous diffusion in porous media. Part 2. - Dry granular materials , 1960 .

[16]  T. J. Marshall.  THE DIFFUSION OF GASES THROUGH POROUS MEDIA , 1959 .