Two-dimensional hetero-spectral correlation analysis has been widely used for the interpretation of spectral changes of humic substances involved in various environmental processes. However, when three different types of spectroscopies are utilised, only a pairwise correlation can be achieved. In order to overcome this problem, a novel method of three-dimensional hetero-spectral correlation analysis with scaling technique was developed in this study, which can further establish a direct correlation between three different types of spectroscopies, including FTIR, ¹³C CP/MAS NMR, and XPS. The proposed method was applied to the fingerprint identification of undissolved humic acid functional groups for Cr(VI) retention, which is one of the most important points for understanding the migration and transformation of Cr(VI) in a subsurface environment. The results indicated that mainly free and dissociated carboxylic groups, phenolic groups, and polysaccharide participated in the reaction with Cr(VI), and these functional groups were mainly located at aromatic domains. Besides, the variations of functional groups were related to the reduction of Cr(VI), and the reduced Cr(III) mainly bound to aromatic domains. The successful application of the proposed method demonstrated that it can serve as a promising tool for further investigations concerning more complicated environmental processes and even other scientific fields by supplying more detailed, reliable and visualised spectral information.

中文翻译：

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一种新的三维异谱相关分析方法，用于指纹识别六价铬保留的腐殖酸官能团†

二维异谱相关分析已广泛用于解释各种环境过程中腐殖质的光谱变化。然而，当使用三种不同类型的光谱学时，只能实现成对相关。为了克服这个问题，本研究开发了一种利用缩放技术进行三维异谱相关分析的新方法，该方法可以进一步建立三种不同类型光谱之间的直接相关性，包括FTIR、 13 C CP ^/ MAS核磁共振和XPS。该方法应用于Cr( VI )保留的未溶解腐植酸官能团的指纹识别，这是了解地下环境中Cr( VI )迁移和转化的最重要点之一。结果表明，主要是游离和解离的羧基、酚基和多糖参与与Cr( VI )的反应，且这些官能团主要位于芳香域。此外，官能团的变化与Cr( VI )的还原有关，还原的Cr( III )主要与芳香域结合。该方法的成功应用表明，它可以通过提供更详细、可靠和可视化的光谱信息，成为进一步研究更复杂的环境过程甚至其他科学领域的有前景的工具。