FIG. 1. Dispersive _s^D (circles) and nondispersive _s^ND (squares) surface free energy components as a function of the gravimetric water content (Fig. 1a) for a clay mineral (data from Chassin et al., 1986) and for a peat soil as a function of the water vapor humidity (Fig. 1b; data from Michel et al. 2001). Schematically shown is the equilibrium film pressure component as a function of moisture content.