Elucidating the 3D chemical and physical architecture of soil microstructures by combining spectromicroscopic techniques and developing of novel computational approaches

土壤微结构仍然被看作是随机排列的矿物和有机成分的非均质混合物，而对于微观尺度下结构形成的建筑原理缺乏深入的了解。尤其是微团聚体(小于250微米的土壤微结构)，这是一种由不同大小和化学成分的矿物和有机成分组成的高度复杂的组合，已知对长期有机物质(OM)的封存起着非常重要的作用。虽然以前不可能在必要的微纳米分辨率下研究复杂的土壤微环境，但现在通过显微和光谱技术的结合，可以在空间上解析完整土壤微结构的组成、三维结构和结构特征。我们假设同一土壤基质上土壤微结构的三维结构强烈依赖于土壤矿物的整体有机质含量(贫C、C中间、富C)和OM质量(高C/N比、低C/N比)与土壤矿物的特定空间排列。为了验证我们的假设，我们将使用矿物学成分相似但有机质含量不同的天然土壤材料。使用天然土壤系统将确保研究有意义的结构性质(如表面粗糙度、孔隙大小、空洞结构)以及促进自然土壤微结构形成的化学信息(如C和N分布)。通过使用LIST中集成到TUM的NanoSIMS中的AFM模块，我们可以将AFM高度剖面与NanoSIMS获得的元素2D/3D信息结合在一起，准确地建立复杂结构的3D样品表面。在自然土壤样品孵化过程中，通过使用13C和15N标记的OM作为OM源，HIM-SIMS将允许在高空间分辨率下确定不同微结构点上有利于有机矿物结合的表面特征，而AFM-NanoSIMS组合将为在高质量分辨率下准确确定元素和同位素OM成分提供地形校正数据。我们的目标是为HIM-SIMS和AFM-NanoSIMS开发相关的表面和体积重建工作流程，以便在微观尺度上准确确定矿物伴生OM的位置和化学性质。我们的研究将提供在微观尺度上追踪自然土壤发育的结构原理的巨大机会，并将能够对土壤3D微观结构中有机-矿物组合的形成进行3D/4D建模。

Soil microstructures are still seen as heterogeneous mixtures of mineral and organic components in random arrangement, while the thorough knowledge about architectural principles governing structure formation at the microscale is lacking. Especially microaggregates (soil microstructures smaller than 250 µm), highly complex associations of mineral and organic constituents of different sizes and chemical composition, are known to play a very important role for long term organic matter (OM) sequestration. While it has previously been impossible to study complex soil microenvironments at the necessary micro- to nanometer spatial resolution, nowadays, by the combination of microscopic and spectroscopic techniques it is possible to spatially resolve the composition, 3D architecture and structural characteristics of intact soil microstructures.We hypothesize that the 3D architecture of soil microstructures on the same soil substrate strongly depends on the bulk OM content (C-depleted, C-intermediate, C-rich) and OM quality (high C/N ratio, low C/N ratio) interconnected with the specific spatial arrangement of soil minerals. To test our hypotheses, we will make use of natural soil material with comparable mineralogical composition but different organic matter content. Using natural soil systems will ensure the study of meaningful structural properties (e.g. surface roughness, pore sizes, cavity structure) together with chemical information (e. g. C and N distribution) fostering the formation of natural soil microstructures.By using the AFM module from LIST integrated into the NanoSIMS at the TUM we can combine the AFM height profiles with the elemental 2D/3D information obtained by NanoSIMS to build the 3D sample surface of complex structures accurately. By using 13C and 15N labelled OM as OM source during the incubation of the natural soil samples, HIM-SIMS will allow the determination of surface characteristics favouring organo-mineral associations at distinct microstructure spots at high spatial resolution, while the AFM-NanoSIMS combination will provide topography corrected data for the accurate determination of the elemental and isotopic OM composition at high mass resolution. We aim to develop correlative surface and volume reconstruction workflows for HIM-SIMS and AFM-NanoSIMS to accurately determine the location and chemical properties of mineral associated OM at the micro-scale. Our study will offer the great opportunity to trace structural principles governing natural soil development at the microscale and will enable a 3D/4D modelling of the formation of organo-mineral associations in soil 3D microstructures.