Figure 3.

Soil P binding affected by Si and Ca measured by XAS. Soft X-ray NEXAFS study on Fe-speciation at the surface of soil particles. Linear absorbance images and respective thickness masks based on the optical density (OD), that were used to extract spectra of two samples of the Peary Land soils each of the soil after Si addition (A), the original soil (B), and the soil after Ca addition (C), at the end of the three months incubation experiments. Scale bars 2 µm. (D) Exemplary Fe 2p spectra of the original soil (dark colours) and after Si addition (bright colours) for three thickness ranges. (E) spectra of pure reference compounds ferrihydrite (FH), goethite (G), siderite (S), and vivianite (V), that were used for the linear decomposition of the measured spectra. (F) Fe(II)-phosphate/Fe_tot ratios plotted against the respective cumulative thickness of Fe_tot, based on the quantitative fits of all acquired datasets.