Alexey I. Sukharev

Kuznetsov’s formula relates the parameters of erosion resistance and soil water stability. However, the mechanism of occurrence of these properties is different: water stability is explained by the action of intra–aggregate hydrophobic bonds in organomineral soil gels, and erosion resistance is explained by water stable aggregates and their adhesion to each other. At the same time, the nature of the interaggregate bonds that ensure erosion resistance remains unclear. The purpose of the work was to clarify the mechanism of erosion resistance of soils and compare it with the mecha- nism of formation of water stability. The work used samples of humus-accumulative soil horizons: sod-podzolic and leached chernozem. To obtain samples with the same aggregate composition, but differing in erosion resistance, it is proposed to use soil polymer ameliorants (SPM). The erosion resistance of soils was determined on a hydrolotter and the critical rate of flushing was calculated. The water stability of the soils was assessed by the blade method. The particle size in the solutions was estimated by laser diffractometry. It was found that on soils treated with SPM, the results of the tray and blade methods correlate by 99%. The high correlation suggests a common nature of intra- and interaggregate bonds. To test the role of hydrophobic interactions in the formation of aggregates resistant to water, polymers of varying degrees of hydrophobicity were added to aqueous humate solutions in a model experiment: polyethylene glycol (PEG), polyacrylamide (PAA) and polyvinyl alcohol (PVA). In parallel, the water stability of soils treated with PEG, PAA and PVA was evaluated. The analysis of the results showed that the greatest water stability of the aggregates was noted when the most hydrophobic polymer, polyvinyl alcohol, was added to the soil, which formed the largest particles when interacting with humate in the model experiment. These results confirm the role of hydrophobic interactions in the formation of aggregates and indicate that when selecting polymer structures, their interaction should be taken into account not with clay minerals, but with soil gels, which include clay minerals and humic substances.

Abstract The decrease in water mobility when the hydrological moisture constant of point of limited availability of water (PLAW) is reached is explained by the presence of film forms of water formed under the influence of the solid phase. It is also known that the existence of such forms of water is limited by the concentration of electrolytes. The aim of the work was to clarify the mechanism of water stabilization by the solid phase of soils in point of limited availability of water, taking into account the colloidal component of soils. The studies were carried out on samples from sod-podzolic and gray forest soils and chernozem. In the work, the value of the PLAW was determined by plotting the secant on the curve of the main hydrophysical characteristic obtained by centrifugation. Scanning electron microscopy, vibrational viscometry, and a technique for extracting gels from soils were also used. During the experiments, it was found that adding 1 n of potassium chloride solution to the soil, compressing the double electric layer on the surface of the particles, does not reduce the value of the PLAW. This suggests that the film forms of water in PLAW are stabilized by soil organomineral gels, since at such concentrations of salts, water films cannot exist in free form. It was also found that an increase in the number of gels in soils by their introduction increases the PLAW of the soil sample, and a decrease in the volume of soil gels leads to a decrease in PLAW. Thus, it is shown that water in case of PLAW is a part of the colloidal component of soils — soil organomineral gels, and the value of PLAW in soils depends on the number and volume of these gels.