| Popis: |
Clay-organic complexation is the dominant mechanism for retention of carbon in soil. Conventional approaches such as density fractionation have some limitations. Now-a-days, spectroscopic and microscopic techniques are being employed for studying clay-organic complexes. Synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectroscopy, synchrotron radiation-based micro-X-ray fluorescence microscopy (μ-XRF) and two-dimensional correlation spectroscopy (2DCOS) analysis, 13 C NMR spectra, synchrotron-based X-ray absorption near-edge fine structure (XANES) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are being used for studying in-depth the mechanisms of clay-organic complexes. The in situ SR-FTIR analysis showed that clay-OH clusters, C–H, C=C, Si–O, and Al–O, were the dominant functional groups throughout soil microaggregates and demonstrated the significantly positive correlation among these functional groups. NMR analysis confirmed the presence of alkyl C, O-alkyl C, aryl C, and carboxyl C in the soil deposits. Spatially resolved observations at the submicron scale with STXM-NEXAFS clearly showed that mineralogy influences SOM stabilization. Detailed identification and quantification about the reactive mineral complexes need to be conducted, which are responsible for locating the key factors of regulating SOM sequestration. Fourier transform ion cyclotron resonance mass spectrometry (FT–ICR–MS), NanoSIMS, and synchrotron scanning transmission X-ray microscopy (STXM) should be integrated to in situ explore molecular structures and binding coordination of soil microaggregates. |
