Sedimentation rate of soil microparticles

Abstract

The aim of the submitted paper is to identify the lower limit of Stokes’ law for calculating the deposition rate of soil microparticles. The authors’ hypothesis on the lower limit of Stokes’ law is based on the idea that with the gradual formation of the colloidal dispersion system, both the particle size and the sedimentation rate decrease. It is assumed that under the lower particle size limit, Stokes’ law does not apply. As a result of the diffusion, the state of the sedimentation equilibrium gradually emerges. The results of the experiment showed that in laboratory conditions, Stokes’ equation ceases to be valid for sedimentation of the particles sized d(90) < 2 μm. During the experiment, a dynamic sedimentation equilibrium was reached at the particle size d(90) = 0.27 μm. The scientific contribution of this knowledge is the accuracy of the determination of hydropedological characteristics dependent on the texture of the soil. In this context, the results stated in the paper define the lower limit of the validity for the laboratory procedures determining soil texture on the basis of the sedimentation methods. To identify the textures below this limit, it is necessary to choose the methods based on other principles. Determination of the lower limit is particularly important in clay soils containing a high proportion of clay particles (clay particles < 2 μm).