用沉降法和激光法测定土壤粒度的对比研究

Comparative Study on Grain-size Measured by Laser Diffraction and Sedimentation Techniques

分别用激光粒度仪和沉降法测定了古水稻土剖面100个样品和下蜀黄土剖面105个样品的粒度分布。对两种测定方法所获结果进行了系统的对比分析。研究结果认为:①沿垂直剖面采集的系列样品不适合于讨论两种方法之间的相关性,质地多样化的表层土壤样品组合较适合讨论该问题;②对于黏粒和砂粒来说,两种方法之间的相关性很好,它们的相关系数分别为0.98和0.93,但激光法所测结果低于沉降法。对于粉粒来说,激光法所测结果明显高于沉降法,但两种方法之间的相关性较差;③沉降法和激光法都不可能测得"真实的"粒度,它们的结果反映了同一样品在不同方面表现出的粒度特点。

Grain-size distributions of ancient paddy soil（n = 100） and Xiashu loess（n = 105） were measured by laser diffraction and sedimentation techniques,the measured results of the two methods were not comparable for soil samples from the vertical-profile series,but comparable for topsoil samples with different textures.Significant correlations between clay fractions and sand fractions existed in the two methods（r = 0.98 and 0.93,respectively）.Both clay and sand fractions obtained by laser diffraction were lower than those by sedimentation techniques,while silt fractions obtained by laser diffraction were clearly higher than those by sedimentation techniques and no significant correlation between the two methods was found.Neither of the two methods can get the ＂real＂ grain-size distribution,the results represent different grain-size characteristics of the same sample.