THE SIMULATION OF GASEOUS DIFFUSION IN SOILS

Computer simulation techniques are presented as a means of applying diffusion theory to two problems concerning the dynamics of oxygen and carbon dioxide distributions in soils. It is demonstrated that these techniques facilitate both problem formulation and solution, and require less mathematical skill than the equivalent analytic techniques. For problems with no analytic solution, simulation can still yield results with an accuracy equal to other numerical methods. Using simulation techniques, it was computed that stationary state conditions for carbon dioxide in a 0·7 cm layer of soil were established 24 hours after waterlogging. Similarly it was computed that for oxygen diffusing through a 0·4 cm layer of soil, equilibrium was attained within six minutes. These data were useful in that they justified the assumptions regarding equilibrium conditions which had necessarily been made in previous experiments. Simulation techniques may be of widespread use, not only for solving diffusion problems, but also for applying other fundamental laws to specific situations.