Quantitative and qualitative characterization of the granulometry of an Inceptisol

Granulometry is an initial factor to be considered in soil research as it plays a fundamental role in physical and chemical properties. The objective of this study was to characterize the granulometric fractions of soil, obtained using the screening and sedimentation method. The Dynamic Light Scattering (DLS), Mid-Infrared (MIR), and Scanning Electron Microscopy with Field Emission Gun (SEM-FEG) techniques were used for this purpose. The quantitative results showed that this soil presents high percentage of clay, followed by fine sand fraction, silt fraction and, finally, the coarse sand fraction. The results obtained by DLS qualify this technique as a procedure to evaluate the quality of the granulometric fractionation of the clay fraction. The MIR analyzes detected characteristic vibrational states of minerals such as kaolinite, halloysite, gibbsite, and quartz. Few works in the literature characterize the clay fraction of the soil without chemical treatment using the SEM-FEG technique. Thus, in this work, pseudo-hexagonal structures were identified, typical of the kaolinite mineral and, to a lesser extent, structures with a filamentous needle-like morphology, which can be ascribed to illite and/or halloysite, whose inorganic functional groups were identified by MIR in the clay fraction of the soil.

粒度分析（Granulometry）是土壤研究中需优先考量的核心因素，因其对土壤的物理与化学性质具有决定性作用。本研究的目标为对通过筛分-沉降法获取的土壤粒度组分进行表征。本研究采用了动态光散射（Dynamic Light Scattering, DLS）、中红外光谱（Mid-Infrared, MIR）以及场发射枪扫描电子显微镜（Scanning Electron Microscopy with Field Emission Gun, SEM-FEG）三种技术完成上述表征工作。定量分析结果表明，供试土壤以黏粒占比最高，其次为细砂粒组分、粉粒组分，最后是粗砂粒组分。动态光散射的测试结果证实，该技术可用于评估土壤黏粒组分的粒度分级质量。中红外光谱分析检测到了高岭石、埃洛石、三水铝石以及石英等矿物的特征振动模式。现有文献中，极少有研究采用场发射枪扫描电子显微镜技术对未经过化学处理的土壤黏粒组分进行表征。因此，本研究在未经过化学处理的样品中识别出了典型高岭石矿物特征的假六方片状结构，同时还少量观测到了丝状针状形貌的结构，此类结构可归为伊利石或埃洛石；前述矿物的无机官能团已通过中红外光谱分析在土壤黏粒组分中得到了确认。