Morin et al. Mononuclear U(IV) complexes and ningyoite as major uranium species in lake sediments Figure 4 (a) Concentration of U(IV) extracted by O2-free NaHCO3 (1M) solution compared to total bulk U. (b) Local structure of mononuclear U(IV)-phosphate/silicate bidendate edge-sharing complexes determined by EXAFS analysis as major solid state species of uranium in the sediments studied (Fig. 2, Table S-3). The phosphate/silicate tetrahedron could be connected to either organic or inorganic substrates. Figure 4 (a) Concentration of U(IV) extracted by O2-free NaHCO3 (1M) solution compared to total bulk U. (b) Local structure of mononuclear U(IV)-phosphate/silicate bidendate edge-sharing complexes determined by EXAFS analysis as major solid state species of uranium in the sediments studied (Fig. 2, Table S-3). The phosphate/silicate tetrahedron could be connected to either organic or inorganic substrates. Morin et al. (2016) Geochem. Persp. Let. 2, 95 - 105 | doi: 10.7185/geochemlet.1610 © 2016 European Association of Geochemistry