Determination of sedimentation speed of soil micro-particles from laser diffraction measurements

Abstract

In hydropedological research and in various scientific experiments, the determination of the settling rate of soil microparticles is a frequent task. Many laboratory procedures for measuring sedimentation rate are based on the Stokes equation. In recent years, methods based on the principle of laser diffraction can be used to measure grain-size distribution and deposition rate of microparticles. The output of the measurements by a laser diffraction method is statistical distribution of soil texture in the measured sample by particle size expressed in % of volume. Measurements were performed in a wet way by MALVERN Instruments device called Mastersizer 2000. The proposed method is based on measuring the time required for soil particles of certain diameter to pass certan distance. The size of soil microparticles present in space and time is defined by probability. Probability is defined in the form of a grain size distribution function. The advantage of the proposed method is its robustness and elimination of human factor errors. This paper presents the results of theoretical approaches and experimental measurements of the settling rate of soil microparticles. Soil samples were taken in the East Slovakian Lowland. Measurements are performed for the selected sizes of soil microparticles for a probability of occurrence of 90%, i.e for d(90). The results are compared with the results calculated by the Stokes equation.