摘要:在我国东北地区，土壤不同程度的受到季节性冻融的影响。冻融作用会改变土壤微观结构，团聚体作为土壤结构的基本单元，其结构特征的改变反映了冻融作用对土壤微观结构的影响。同步辐射显微CT可以无损获取高分辨率、强对比度的内部结构图像，是研究土壤团聚体三维微结构的有效手段。采集了室内冻融循环试验下不同冻融循环次数的土壤团聚体样品，应用同步辐射显微CT扫描获取了3.25 μm分辨率的团聚体内部结构图像，然后应用CT图像处理方法和Image J软件观察并定量分析了团聚体微结构特征。结果表明：随着冻融循环次数的增加，土壤孔隙度不断增大，瘦长型孔隙度占比与>100 μm的非毛管孔隙度不断增大；当冻融循环次数达到7次以上，团聚体孔隙连通度随冻融循环次数的增加而变大。冻融循环对黑土团聚体孔隙度、孔隙形状、孔隙分级、连通性等结构特征影响显著。该研究为春季解冻期土壤侵蚀机理的研究及水土流失的防治提供理论依据。



Abstract:In Northeast China, seasonal freezing and thawing have been shown to cause significant physical changes in soil. The change in soil microstructure might be attributed to the freeze-thaw action during early spring. The freeze-thaw action affects soil microstructure directly by affecting soil aggregate, which is the basic unit of soil structure. Synchrotron-based X-ray micro-computed tomography can nondestructively capture images of the interior structure with high resolution and strong contrast, and therefore, is an excellent tool to investigate the 3-D microstructure of soil aggregates. Samples of soil aggregates were collected from laboratory freeze-thaw tests with different number of freeze-thaw cycles, and the aggregates were scanned with micro-CT at a resolution of 3.25 μm. The microstructure of aggregates was visualized and quantified by the digital image analysis method using Image J software. The results showed that with the increase in number of freeze-thaw cycles, the soil porosity increased, and the proportion of extended pore and pores > 100 μm also increased. When the number of freeze-thaw cycles was >7, the aggregate porosities increased with the increase in number of freeze-thaw cycles. The results showed that the number of freeze-thaw cycles significantly influenced the structural characteristics of black soil aggregates. This study provides a theoretical basis for the study of freeze-thaw erosion and control of soil erosion during thawing in spring.





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