Mapping Phosphorus Availability in Soil at a Large Scale and High Resolution Using Novel Diffusive Gradients in Thin Films Designed for X-ray Fluorescence Microscopy

Research output: Contribution to journalArticleResearchpeer-review


  • Claudia Moens
  • Enzo Lombi
  • Daryl L. Howard
  • Justin L. Payne
  • Peter M. Kopittke
  • Casey L. Doolette

External Organisational units

  • University of South Australia
  • Katholieke Universiteit Leuven
  • Australian Synchrotron
  • School of Chemical Engineering, The University of Queensland


A novel binding layer (BL) as part of the diffusive gradients in thin films (DGT) technique was developed for the two-dimensional visualization and quantification of labile phosphorus (P) in soils. This BL was designed for P detection by synchrotron-based X-ray fluorescence microscopy (XFM). It differs from the conventional DGT BL as the hydrogel is eliminated to overcome the issue that the fluorescent X-rays of P are detected mainly from shallow sample depths. Instead, the novel design is based on a polyimide film (Kapton) onto which finely powdered titanium dioxide-based P binding agent (Metsorb) was applied, resulting in superficial P binding only. The BL was successfully used for quantitative visualization of P diffusion from three conventional P fertilizers applied to two soils. On a selection of samples, XFM analysis was confirmed by quantitative laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The XFM method detected significant differences in labile P concentrations and P diffusion zone radii with the P fertilizer incubation, which were explained by soil and fertilizer properties. This development paves the way for fast XFM analysis of P on large DGT BLs to investigate in situ diffusion of labile P from fertilizers and to visualize large-scale P cycling processes at high spatial resolution.


Original languageEnglish
Pages (from-to)440-448
Number of pages9
JournalEnvironmental science & technology
Issue number1
Publication statusPublished - 18 Dec 2023