基于同步辐射微CT研究不同利用年限水稻土团聚体微结构特征

Characterization of aggregate microstructure of paddy soils cultivated for different years with synchrotron based micro-CT

同步辐射微CT(SRμ-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。本研究采集了种植水稻20a和40a后表层土壤团聚体样品,应用SRμ-CT扫描获取了9μm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3DMA-Rock软件观察并定量分析了团聚体微结构特征。随着种植水稻年限的增加,土壤有机质含量和全氮含量显著增加,团聚体孔隙数量和孔隙度显著增加,比表面积显著增大。种植水稻20a的土壤团聚体呈现致密的黏闭结构,而种植水稻40a的土壤团聚体具有由团粒状小团聚体构成的复杂多孔微结构。结果表明随着种植年限的增加,团聚体微结构和土壤质量明显改善。

Synchrotron based X-ray micro-computed tomography （SRμ-CT） can nondestructively capture images of the interior structure with high resolution and strong contrast, and is therefore an excellent tool to investigate the 3-D microstructure of soil aggregates. Aggregates with diameters around 5 mm were collected from paddy soils with rice cultivation for 20 and 40 years, respectively, and the aggregates were scanned with SRμ-CT at a resolution of 9 μm. Aggregate microstructure was visualized and quantified using digital image analysis method and 3DMA-Rock software. Results showed the SOM and total nitrogen content significantly increased after 40 years of rice cultivation compared with 20 years of rice cultivation. The number of pores, porosity, and the specific surface area of soil aggregate significantly increased with the increase of cultivation years. Aggregates of paddy soil with 20 years rice cultivation had a dense massive microstructure with few connected pores, while the aggregate with 40 years rise had a more heterogeneous porous microstructure. The results indicated significant improvement of aggregate microstructure and soil quality with the increase of rice cultivation years.