Introductory overview to the special issue papers on synchrotron radiation in soil and geosciences.

This paper presents P K-edge XANES spectra of orthophosphate and inositol hexakisphosphate (IHP) adsorbed to important pedogenic minerals and soil organic matter in moderately acidic soils, as well as of IHP retained by calcite and Ca phytate, which are important P forms in calcareous soils. Inclusion of these spectra in addition to spectra of well known P-bearing compounds supposed to be present in soils (free and cation-bound IHP, Al, Fe, Ca phosphate minerals) as reference compounds in linear combination fitting exercises improves fit quality and yields more accurate P speciation results.

Fe-bound soil phosphorus (P) is probably often underestimated by LCF (linear combination fitting) conducted on P K-edge X-ray absorption near-edge structure (XANES) spectra, unless inositol hexaphosphate (IHP) adsorbed to ferrihydrite and IHP adsorbed to goethite are included as reference compounds.

X-ray spectromicroscopy is a tool excellently suited to studying materials from geo- and environmental sciences, and combines high spatial resolution with high spectral resolution, thus connecting morphology with chemistry. Using tomography or the newly developed coherent diffraction imaging, three-dimensional information about the structure of samples on the micro- and nanoscale can be obtained.

Quantification of the amorphous phases in soil-related material micro-samples was achieved with an advantageous refinement methodology that carefully separates the instrumental profile parameters leaving a reduced number of sample-related parameters.

A deep neural network approach to the identification and quantification of powder X-ray diffraction patterns was applied and proved successful for the quantitative description of complex mineralogical assemblages consisting of up to four minerals with different structures, including different space groups, for which data augmentation is not straightforward.

Partial least-square (PLS) regression was used to evaluate mixtures of Cd L₃-edge spectra of references compounds and the obtained PLS model was then applied to a soil sample in order to qualify and quantify the Cd species therein.

X-ray absorption near-edge structure (XANES) spectroscopy has been used to examine forms of aluminium (Al) in plants, with K-edge XANES suitable for identifying tetrahedrally and octahedrally coordinated Al. However, the poorer detection limit of L-edge XANES limits its use for plant tissues but, nevertheless, XANES analyses of Al in plants are of value where Al forms differ markedly.

The discovery of naturally occurring metal–organic framework (MOF) minerals highlights the connection between crystal engineering and mineralogy. It is shown how classification of such organic minerals rests on concepts of supramolecular chemistry, coordination chemistry and crystal engineering.

Leek roots can physiologically convert about 80% of environmental lead into insoluble lead phosphate and lead carbonate, and leek leaves also contain similar proportions of lead phosphate and lead carbonate. An essential mechanism of Pb detoxification is the development of significant amounts of lead precipitation and immobilization on the root epidermis and other inner surfaces.