Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824, United States.
Research Institute of Agricultural Resources and Environment, Jilin Academy of Agricultural Science, Changchun, 130033, China.
Environ Sci Technol. 2020 Jul 21;54(14):8980-8989. doi: 10.1021/acs.est.0c01028. Epub 2020 Jul 1.
Challenges with visualization of nonparticulate organics in porous materials limit understanding and modeling processes of transport, decomposition, and storage of organic compounds. In particular, it impedes deciphering the mechanisms driving accumulation and protection of soil organic matter (SOM), processes crucial for sustaining soil fertility and mitigating effects of global climate change. A recently proposed method of staining soil organics by OsO vapors with subsequent dual-energy X-ray computed microtomography scanning (μCT) offers new opportunities to visualize SOM within intact soil matrix. Our objective was to test the method's performance in staining different organic materials located in media with contrasting pore characteristics: (1) roots of switchgrass ( L.), either placed within fine and coarse sands or grown within soil microcores, (2) biochar fragments, and (3) soils with relatively low and high C contents. We found that the method was effective in staining organic materials of root origin and the organics associated with fine soil particles, but not the biochar. The estimated percent of total C that reacted with OsO vapors ranged from 0.7% in plant roots to 3.2% in sand-free fraction of the high C soil and was only 0.2% in the studied biochar. Total soil C and Os concentrations were strongly linearly related, suggesting a potential for future method development. However, we would recommend caution when interpreting the results in cases when gas diffusion through the soil matrix is limited.
多孔材料中非颗粒有机物的可视化挑战限制了对有机化合物传输、分解和存储过程的理解和建模。特别是，这阻碍了对驱动土壤有机质（SOM）积累和保护机制的解读，而这些过程对于维持土壤肥力和减轻全球气候变化的影响至关重要。最近提出的一种通过 OsO 蒸气对土壤有机物进行染色的方法，随后进行双能 X 射线计算机微断层扫描（μCT）扫描，为在完整土壤基质中可视化 SOM 提供了新的机会。我们的目的是测试该方法在染色不同有机材料时的性能，这些有机材料位于具有不同孔隙特征的介质中：（1）柳枝稷（ L.）的根，要么放置在细砂和粗砂中，要么生长在土壤微芯内，（2）生物炭碎片，以及（3）C 含量相对较低和较高的土壤。我们发现，该方法在染色根源性有机物质和与细土颗粒相关的有机物方面非常有效，但对生物炭无效。与 OsO 蒸气反应的总 C 的估计百分比范围从植物根中的 0.7%到无砂高 C 土壤的 3.2%，而在研究的生物炭中仅为 0.2%。总土壤 C 和 Os 浓度呈强线性相关，这表明未来可能会开发该方法。然而，我们建议在气体通过土壤基质扩散受到限制的情况下，谨慎解释结果。
