WATER VAPOR ADSORPTION KINETICS AND ISOTHERMAL INFILTRATION

Abstract

Water vapor transport and adsorption may be a significant factor affecting solution movement through relatively dry, fine-textured soils. The significance of this process depends on the relative magnitudes of the liquid and vapor diffusivities in the water content range in which vapor adsorption is possible. Dependence of the vapor diffusivity on vapor adsorption leads to incorporation of the kinetic aspects of adsorption into the vapor diffusivity. As such, significant fluxes of water vapor adsorbing ahead of the liquid wetting front may occur during relatively slow rates of infiltration on the order of 1 mm/d. Several infiltration experiments were conducted to assess the effects of vapor adsorption kinetics on liquid-vapor diffusivity. Results from these experiments indicated that, as boundary flux increased, the range of water contents over which vapor diffusivity dominates tended to become increasingly narrow. Based on these results and observations of liquid-wetting front advance rates and vapor adsorption, it appears that the significance of vapor transport and adsorption phenomena to solution movement in fine-textured soils decreases as the boundary flux and initial water content increase.