Light and heavy element detection in thin sections of soils with the ion microprobe mass analyzer (IMMA)

Previous research with the scanning electron microscope (SEM)-energy dispersive X-ray analyzer (EDXRA) and the electron microprobe analyzer (EMA), showed that the detection of light elements in thin sections of soils was problematic or even impossible. Consequently, initial experiments were performed with the ion microprobe mass analyzer (IMMA). These investigations were carried out on a piece of root material in soil (containing both light and heavy elements) which has a 'clayey' appearance and is known as a clayified root. The presence of heavier elements in this sample was investigated by SEM-EDXRA prior to IMMA analysis. The results showed that all chemical elements could be analyzed in the plant fragment. Also much higher elemental detection sensitivities were found with IMMA as compared to SEM-EDXRA and EMA. This even allowed ion imaging of trace elements. High-quality ion images of both light and heavy elements could be obtained in much shorter exposure times than with SEM-EDXRA and EMA techniques. Furthermore by analysis of fragmentation ('fingerprint') spectra additional information was obtained with respect to the chemical binding of the analyzed elements. From these preliminary results it became clear that IMMA offers full possibilities for microchemical analysis in situ of all important elements in soil specimens, these offering increased possibilities in soil micromorphology