Particle size analysis by laser diffraction

Abstract: Particle size distribution is a fundamental property of any sediment or soil, and particle size determination can provide important clues to sediment provenance. For f ensic work, the par-ticle size distribution of sometimes very small samples requires precise determination using a rapid and reliable method with a high resolution. A protocol has been developed using a Coulter TM LS230 laser granulometer, which can analyse particles in the size range 0.04 p~m-2000 &m. The technique is essentially non-destructive, permitting the recovery of critical samples, and has been demon-strated to have high precision for a range of soils, sediments and powders of interest in forensic investigations. Size is a fundamental property of sediment particles, affecting their entrainment, transport and deposition. Particle size analysis therefore provides important clues to the sediment provenance, transport history and depositional conditions (e.g., Krumbein 1941; Friedman 1979; Sheridan et al. 1987; Bui et al. 1989) and, in a forensic ontext, offers a potentially useful means of 'fingerprinting ' soils and sediments for pur-poses of comparison and environmental interpreta-tion. The various techniques employed in particle size determination i clude direct measurement, dry and wet sieving, sedimentation, and measurement by laser granulometer, X-ray sedigraph and Coulte