Fig. 4. Influence of fluid-phase (water or air) content, soil volumetric surface area (SA_vol), and content of large pores (₁₀₀) on tortuosities in (a) the soil liquid phase and (b) the soil gaseous phase. Solid lines are calculated from Eq. [10] combined with Eq. [3] through [7], assuming = 0.5. Open triangles are data from literature for gas diffusion in completely dry soil