激光粒度仪测试结果及其与沉降法、筛析法的比较

分析了Cilas 940L激光粒度仪的测试结果,并与沉降法、筛析法进行了比较。激光粒度仪测试结果的重复性较好,测量精度较高。对于玻璃珠样品,激光粒度仪和筛析法测试结果十分接近,对于天然沉积物,激光粒度仪测定的平均粒径偏粗,分选偏差。和沉降法相比,激光粒度仪测定的粘土组份 (<8%)的含量为沉降法的 46.7%～ 70.5 %,平均为 6 0 %,测定的平均粒径较沉降法偏粗,分选偏差。造成激光粒度仪与沉降法、筛析法之间差异的原因主要在于这些测试方法原理的不同和天然沉积物不规则的形状。

Evaluation of a Wide Range Laser Particle Size Analyses and Comparison with Pipette and Sieving Methods

It is important to examine the performance of a laser particle size analyser and understand the discrepancy between it and pipette and sieving methods. In the present study, the results obtained using a Cials 940 L are evaluated and compared with pipette and sieving methods using natural and artificial sediment samples. Two procedures were used to test the reproducibility of Cilas 940 L, which show that the variability of statistical parameters (mean, sorting, skewness and kurtosis) is low,indicating that the reproducibility of Cilas 940 L is satisfactory. According to the measurement of 15 mud samples, the laser sizer underestimates the fraction of clay particles with an efficiency of detection proportional to the clay content determined from pipette analysis. The results obtained with the Cilas 940 L show somewhat greater mean size and lower sorting than the pipette method. The results of measurement on glass particles by Cilas 940 L are in agreement with the sieving method but have larger mean sizes and lower sorting than sieving analysis for natural sediment. Differences in the results between the laser method and pipette/sieving methods may be attributed to the various principles of the methods and the particle property (e.g. non sphericity of particles). For a geologist, it should be realized that there are limitations of modern instruments,and the grain size data obtained by different methods must be utilized and analysed in an appropriate way.