激光粒度仪与吸管法测定土壤机械组成的比较研究——以不同退化程度栗钙土为例

Comparison of Laser Diffraction Method and Pipette Method on Soil Particle Size Distribution Determination——A Case Study of Variously Degraded Kastanozem

激光粒度仪法作为测量土壤机械组成的新型方法,具有操作简单、速度快的优势,但其适用性与可靠性尚未达成广泛共识。为探究激光粒度仪测定土壤机械组成的准确性与适用性,采集7种退化程度共21份栗钙土土样,使用激光粒度仪与吸管法测定土样机械组成并对比分析。结果显示:激光法测定结果黏粒偏小,而砂粒、粉粒偏大,且随粒径减小误差增大。将两种测定结果进行回归分析,发现砂粒与粉粒转换模型拟合效果理想,黏粒拟合效果差。建立质地三角图发现两种方法得到的质地差异较大,采用转换后数据分析质地,发现质地接近、正确率高,转换效果好。通过扫描电镜对土粒形态观察,发现标准流程不同分散方法下土粒形状与数量均有差异,推测分散方法会影响土壤机械组成的测定结果。激光粒度仪的适用性据测定对象的不同而有差异,对黏粒精度要求高的情况下不宜使用该法,而其他情况下需要对测定结果进行数据转换。

The laser diffraction method(LDM)has become a new method for particle size analysis.It is simple and convenient.However,its applicability and reliability have not been fully confirmed yet.In order to investigate the reliability and applicability of LDM,21 Kastanozem soil samples with seven different degradation levels were collected and their particle size distributions were measured using both LDM and pipette method.The results showed that LDM underestimated the clay content and overestimated the sand and silt contents.The difference of the results measured by the two methods increased as particle sizes decreased.Regression analysis showed that there were high correlations between the sand and silt contents determined by these two methods,but there was no correlation for the clay content.Triangle coordinate diagram was applied to compare the textures determined by these two methods.The results agreed well after a transformation based on regression analysis compared to the original results.The morphology of soil particles was observed using a scanning electron microscope.The results showed that the shape and number of soil particles were different under different standard dispersive treatments which were involved in different methods,and would influence the results of particle size distribution.The applicability of LDM depends on the types of soil samples.If there are high precision requirements of clay content,LDM is not a good choice,in other cases,LDM is a feasible solution but the results should be carefully checked and transformed.