Study of Porosity of Soils and Soil Minerals Modified by Adsorbed Humic Acid by the Method of Mercury Porosimetry

Experimental determination of porosity and pore size distribution by mercury porosimetry has shown that adsorption modification of the surface of kaolinite, montmorillonite, palygorskite, quartz sand, gray forest soil (Eutric Luvisol (Loamic, Cutanic, Ochric), as well as chernozem (Luvic Chernozem (Loamic, Pachic)), by humic acid (HA) has little effect on total porosity and total pore volume, but affects differential pore volume values and pore size distribution (crypto-, ultramicro-, meso-, and macropores). For soils exposed to humic acids, greater stability of the structure and a significantly more homogeneous distribution of the differential porosity were revealed. The effect of the adsorption of humic acid on the structural–sorption properties of minerals and soils is important in the context of understanding formation of soil adsorption complex and regulation of the structural and water-physical properties of soils and soil fertility management.