Nature of Bonds in the Formation of Water Stability of Soil Aggregates

Abstract

Abstract The opinion exists that water stability is provided by hydrophobic bonds between organic soil particles; however, there are works in which the main role in the occurrence of this property is assigned to the presence of hydrophilic organic substances in soils. The goal of this study is to clarify the nature of the bonds (hydrophilic or hydrophobic) that ensure the water stability of soils. We used samples of sod-podzolic and gray forest soils, as well as leached chernozem. Experiments to assess water stability were carried out using the method of “blades.” It is based on the dissection of linearly arranged aggregates, which were preliminarily moistened in vacuum to values close to saturation. The energy of hydrophobic bonds depends on the temperature; therefore, the influence of temperature on the value of the determined water stability was studied. Experiments showed that, as the temperature increases, the water stability of aggregates stored in the wet state increases from the moment of selection and decreases as the temperature increases. This indicates the leading role of hydrophobic bonds in the formation of water stability. As for the samples dried to an air-dry state, moistened again, and kept wet for more than two weeks, no temperature dependence of the water stability has been found. Taking into account that the strength of hydrophobic bonds increases with increasing temperature, while that of hydrophilic bonds decreases, the obtained data immutability of water stability can be explained if we assume the joint participation both hydrophobic and hydrophilic bonds in water stability of soil samples that have passed through the stage of drying to an air-dry state. In fact, these results indicate a strong change in the structural organization of soils during drying.