Volatile-Type Solute

Use this command to specify soil surface boundary condition for volatile solutes that are present in both the liquid and gas phases. This situation requires modification of the usual third-type boundary condition by including an additional term to account for gaseous diffusion through a stagnant boundary layer of thickness d on the soil surface. The additional solute flux is assumed proportional to the difference in gas concentrations above and below the boundary layer [Jury et al., 1983].

See also the "How to Edit Boundary Conditions" topic.