Environ Sci Technol. 2015 Jan 20;49(2):1035-42. doi: 10.1021/es505271p.
Synchrotron-based soft-X-ray scanning transmission X-ray microscopy (STXM) has the potential to provide nanoscale resolution of the associations among biological and geological materials. However, standard methods for how samples should be prepared, measured, and analyzed to allow the results from these nanoscale imaging and spectroscopic tools to be scaled to field scale biogeochemical results are not well established. We utilized a simple sample preparation technique that allows one to assess detailed mineral, metal, and microbe spectroscopic information at the nano- and microscale in soil colloids. We then evaluated three common approaches to collect and process nano- and micronscale information by STXM and the correspondence of these approaches to millimeter scale soil measurements. Finally, we assessed the reproducibility and spatial autocorrelation of nano- and micronscale protein, Fe(II) and Fe(III) densities in a soil sample. We demonstrate that linear combination fitting of entire spectra provides slightly different Fe(II) mineral densities compared to image resonance difference mapping but that difference mapping results are highly reproducible between among sample replicates. Further, STXM results scale to the mm scale in complex systems with an approximate geospatial range of 3 μm in these samples.
基于同步加速器的软 X 射线扫描透射 X 射线显微镜（STXM）具有提供生物和地质材料之间关联的纳米级分辨率的潜力。然而，如何准备、测量和分析样品，以使这些纳米级成像和光谱工具的结果能够扩展到现场规模的生物地球化学结果的标准方法尚未得到很好的确立。我们利用一种简单的样品制备技术，允许在土壤胶体中评估详细的矿物、金属和微生物光谱信息，达到纳米和微米级。然后，我们评估了通过 STXM 收集和处理纳米和微米级信息的三种常见方法，以及这些方法与毫米尺度土壤测量的对应关系。最后，我们评估了土壤样品中纳米和微米级蛋白质、Fe(II)和 Fe(III)密度的重现性和空间自相关性。我们证明，与图像共振差映射相比，对整个光谱进行线性组合拟合略微提供了不同的 Fe(II)矿物密度，但差异映射结果在样品重复之间具有高度重现性。此外，STXM 结果在具有复杂系统的毫米尺度上具有可扩展性，在这些样品中，其地理空间范围约为 3 微米。
