ASSESSMENT OF SPECIFIC SURFACE AREA AND POROSITY OF SUBSOILS

Soils and subsoils have a complex structure consisting of several elements with different morphology and chemical composition, combining micro-, meso-, and macroporous substructures. Classical approaches, such as Brunauer-Emmett-Teller (BET) or Barrett-Joyner-Halenda (BJH) methods, cannot provide an accurate assessment of morphological characteristics of such solids, nor can do modern sophisticated numerical methods which depend on idealized models of pores that hardly reflect a real morphology of heterogeneous solids in question. The present study describes a way to overcome this difficulty by applying a combination of the alpha S-plot technique and a modified Remy-Poncelet method. The proposed approach allowed estimating the volumes of the untramicropores, supermicropores and the sum of meso- and macropores as well as the specific surface areas of the solid without ultramicropores and of the solid without all micropores. The former specific surface area is a more reasonable estimate of the area available for layer coverage than the BET specific surface area, and all together these characteristics provide a detail description of solid's morphology. Subsoil samples excavated from different depths were used as exemplary solids. They mostly consisted of quartz, feldspar, and clay minerals and had different sorts of pores associated with the clay fraction and soil aggregates as well as a relatively large fraction of non-porous sand particles. Relations of the morphological properties with subsoil profile and mineralogical composition are discussed.