New opportunities to unravel the microarchitecture of mineral and organo-mineral associations by NanoSIMS using the upgraded O source

NanoSIMS (nanoscale secondary ion mass spectrometry) allows unique elemental and isotopic analyses at nanometer spatial resolution and provided challenging insights into the architecture of soil organo-mineral constituents and valuable knowledge of crucial processes taking place at the microscale.

The NanoSIMS instrument is equipped with two ion sources: the Cesium source (Cs+) convenient to detect ions related to organic matter distribution and the Oxygen source (O-) favourable to provide information on mineral phases or metals in samples.

In this contribution a diverse range of case studies will be presented highlighting analytical and experimental applications of the NanoSIMS upgraded with an improved RF plasma O-source as recently installed at the TUM. With a spatial resolution down to 50nm and high stability, the upgraded O- source is now best suitable for probing elemental and isotopic composition of minerals at the microscale, which provides ample opportunities for novel experimental applications.

Furthermore, extended analyses of soil organo-mineral associations are possible with both Cs+ and O- sources at similar resolution. This enables novel combinations of C, N, P and Si distributions depicted by the Cs+ source with the distribution of e.g. Na, Mg, K, Ca and advanced measurement of Fe and Al as revealed by the O- source. Post-processing tools for unsupervised clustering and supervised segmentation facilitate the comparison and quantitative analysis of the spatial architecture within intact soil structures.

These recently developed techniques provide an innovative platform to extend our understanding of biogeochemical processes taking place at organo-mineral and mineral-mineral interfaces at the microscale.