Volume‐related quantification of organic carbon content and cation exchange capacity of macropore surfaces in Bt horizons
Volume‐related quantification of organic carbon content and cation exchange capacity of macropore surfaces in Bt horizons
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DOI：
10.1002/vzj2.20069
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发表时间：
2020-01
影响因子：
2.8
通讯作者：
M. Leue;D. Uteau;S. Peth;S. Beck-Broichsitter;H. Gerke
中科院分区：
文献类型：
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作者：
M. Leue;D. Uteau;S. Peth;S. Beck-Broichsitter;H. Gerke
在结构化土壤中，蚯蚓洞穴、根通道、收缩裂缝和团聚空间形成复杂的大孔网络，与优先运输、周转过程和根系生长相关。大孔壁通常涂有有机矿物材料，这些材料决定了润湿性、吸附性和阳离子交换容量 (CEC) 等物理化学特性。这里的目标是确定来自黄土和冰耕土形成的 Luvisols Bt 层的较大完整土芯（约 7,500 cm3）的体积平均平均大孔涂层特性。大孔表面有机碳 (OC) 含量和 CEC 的量化基于 231 μm 体素分辨率的 X 射线计算机断层扫描 (XRCT) 三维图像和区分生物孔和裂缝的血管程序。大孔表面积与大孔涂层材料的 OC 含量和 CEC 的毫米级数据相结合。占样品体积 5.6%（黄土-Bt）和 4.6%（till-Bt）的大孔表面约占土壤 OC 含量和 CEC 的三分之一。在大孔中，较大生物孔的表面对土壤核心的 OC 含量贡献最大。覆盖裂缝和针孔填充对耕地-Bt 的 OC 含量的贡献大于黄土-Bt。局部较高的 OC 含量和 CEC 值强调了 Luvisols Bt 层位中大孔表面作为地球化学热点和质量交换的作用，特别是在优先流动和传输过程中。基于体积的涂层特性可能有助于改善宏观尺度的双域流动和传输模型。
In structured soils, earthworm burrows, root channels, shrinkage cracks, and interaggregate spaces form complex macropore networks relevant for preferential transport, turnover processes, and root growth. Macropore walls are often coated with organomineral material, which determine physicochemical properties such as wettability, sorption, and the cation exchange capacity (CEC). The objective here was to identify volume‐averaged mean macropore coating properties of larger intact soil cores (∼7,500 cm3) from Bt horizons of Luvisols developed from loess and glacial till. The quantification of organic C (OC) content and CEC of macropore surfaces was based on three‐dimensional images of X‐ray computed tomography (XRCT) of 231‐μm voxel resolution and a vesselness procedure to distinguish between biopores and cracks. Macropore surface areas were combined with millimeter‐scaled data of OC contents and CEC of macropore coating material. The surface of macropores that accounted for 5.6 % (loess‐Bt) and 4.6 % (till‐Bt) of the samples’ volumes represented approximately one‐third of the OC content and CEC of the bulk soil. Among the macropores, surfaces of larger biopores contributed most to OC content of the soil cores. The contribution of coated cracks and pinhole fillings to OC content was larger for the till‐Bt than for the loess‐Bt. Locally higher OC contents and CEC values emphasize the role of macropore surfaces in Bt horizons of Luvisols as geochemical hotspots and for mass exchange, especially during preferential flow and transport. Volume‐based coating properties may help improving macroscopic‐scale two‐domain flow and transport models.