  The pore-solid interface and its characteristics play a key role in chemical
interactions between minerals in the solid soil matrix and the liquid in pore
space and, consequently, solute transport in soils. Specific surface area
(SSA), typically measured to characterize the pore-solid interface, depends not
only on the particles size distribution, but also particle shapes and surface
roughness. In this note, we investigate the effects of surface roughness and
probing molecule size on SSA estimation, employ concepts from fractals, and
theoretically estimate specific surface area from particle size distribution
and water retention curve (WRC). The former is used to characterize the
particle sizes and the latter to approximately quantify the pore-solid
interface roughness by determining the surface fractal dimension Ds. To
evaluate our approach, we use five Washington and twenty one Arizona soils for
which both particle size distributions and water retention curves were
accurately measured over a wide range of particle sizes and matric potentials.
Comparison with the experiments show that the proposed method estimates the SSA
reasonably well with root mean square error RMSE = 16.8 and 30.1 m2/g for the
Washington and Arizona datasets, respectively.
