|
| Methodology | Sample specifications | Depth of analysis | Probe type | Implementations | References |
|
| Scanning electron microscope energy dispersive spectroscopy (SEM-EDS) | Pressure in the tens of torr range, with an element content exceeding 1% | Surface | Electronic | Analyzing the composition and arrangement of soil, offering details on chemical elements, and visually assessing and describing microaggregates | [131, 132] |
| X-ray photoelectron spectroscopy (XPS) | Ultra-high vacuum | Surface | Photoelectron | Composition of elements (dehydrogenation) in various forms of C, N, and O | [133] |
| Micro-X-ray fluorescence microscopy (XRF) | Flexible, micron-thin layer with element content measured in parts per million (ppm) | Variable | X-ray absorption | The makeup and chemical condition of metallic elements, with the exception of C complexes | [134, 135] |
| Electron probe microanalysis | High vacuum | Surface (micrometer) | Electronic | The elemental composition and dispersion, coupled with the spatial arrangement and interactions among inorganic and organic components | [136, 137] |
| Nuclear magnetic resonance spectroscopy | Extraction of paramagnetic compounds | — | — | Semiquantification of functional groups and recognition of components (C, N, P) | [138] |
| STXM | Low vacuum, helium, thin layer | Pierce through | X-ray | Enhanced examination of elemental composition and chemical forms pertaining to C, O, and N, encompassing elemental speciation analysis and mapping | [139, 140] |
| Fourier transform infrared spectroscopy (FTIR) | Flexible, and micron-thin layer | Micrometer | Infrared light | Chemical composition of OM and minerals | [141] |
| Nano-scale secondary ion mass spectrometry (NanoSIMS) | High vacuum at 10−10 bar, smooth sample surface, with element contents measured in parts per billion (ppb) to parts per million (ppm) | Surface | Ion source | Visualizing and characterizing OM and minerals, with a particular focus on isotope mapping | [59, 72] |
| Infrared spectroscopy | Micrometer thin layer, frozen section | Micrometer | Infrared light | Cartographing OM distribution on aggregate surfaces and delineating the distribution of functional groups | [142] |
| X-ray computed microtomography | Cylinders measuring 1 mm × 5 mm, extracted from cores with a diameter of 10 cm | Centimeter | X-ray | The findings enable a complete reconstruction of the pore network | [143] |
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