PARTICLE-SIZE ANALYSIS OF SOILS USING LASER-LIGHT SCATTERING AND X-RAY-ABSORPTION TECHNOLOGY

The particle-size distribution for the fine-grained fraction of eleven soil samples was determined using four commercially available, state- of-the-art automated particle-size distribution analysis instruments. Two of the instruments operate on the principle of interaction of lase r light with soil particles suspended in water in a highly agitated st ate, and two operate on the principle of the absorption of an X-ray be am by a suspension of soil particles settling in a quiescent column of water. The results from each instrument for each soil sample were com pared to size analysis data determined by the hydrometer technique. Th e X-ray absorption instruments produced particle-size distributions ve ry close to those of the hydrometer method, with the exception of soil s with high mica concentrations. The laser-based instrument data did n ot agree as well with the hydrometer data, although for soils with sig nificant mica contents the results were closer than the results from t he X-ray absorption instruments. Based on these results, however, it a ppears that the automated X-ray absorption/sedimentation-based instrum ents show promise as alternatives or as a possible supplement for the manual hydrometer method of size analysis for soils without significan t mica particle concentrations.