Estimating Oxygen Diffusion Ratio and Air Permeability by Using Amount of Soil Moisture

Gas diffusion ratio in the soil compared to its diffusion in the atmosphere (DP/D0) and air permeability in the soil (Ka) is a function of soil physical characteristic، including pore size، pore continuity، and air porosity. Also، gas diffusion in soil is different based on the shape، moisture content، size، and pore tortuosity. In this study، 30 soil samples from different textural classes were prepared as undisturbed soil using a steel cylinder. At different moisture contents، DP/D0 values were measured with oxygen diffusion unsteady method and Ka was measured using falling head method. Finally، DP/D0 and Ka changes at various soil moisture levels and regression equations showing their relation were obtained. The results indicated that with increasing soil moisture، DP/D0 and Ka decreased as logarithmic function such that the maximum values of these two properties were achieved at low soil moisture and their minimum values at near saturation moisture. The obtained R2 values for DP/D0 and Ka (0. 75 and 0. 58، respectively) showed that، assuming other soil physical properties remain constant، we could use these relationships to estimate DP/D0 from the amount of soil moisture with relatively good accuracy and considerable reliability، thus، by this method، the direct measurement of these two properties is not required.