Untersuchungen zu Redoxprozessen von Uran in Mischkulturbiofilmen und spektroskopische Verifizierung von ultradünnen Mineralüberzügen auf „Depleted Uranium“ mit Laser- Fluoreszenz- Techniken


Untersuchungen zu Redoxprozessen von Uran in Mischkulturbiofilmen und spektroskopische Verifizierung von ultradünnen Mineralüberzügen auf „Depleted Uranium“ mit Laser- Fluoreszenz- Techniken

Arnold, T.; Großmann, K.; Baumann, N.

Particles of U(V) and U(VI) were observed in vivo in a living multispecies biofilm by a combined laser-induced fluorescence spectroscopy (LIFS) and confocal laser scanning microscopy (CLSM) approach. The fluorescent uranium particles were located at the bottom and at the edges of biofilms colonies and ranged in size from up to 20 µm in length to 7 µm in width. Laser fluorescence spectroscopy was applied to identify these uranium particles. They showed either a characteristic fluorescence spectrum in the wavelength range of 415-475 nm, indicative for U(V), or in the range of 480-560 nm, which is typical for U(VI). The particles of U(V) as well as U(VI) were simultaneously observed in the biofilms. For U(VI) the particles were attributed to biologically mediated precipitation and for U(V) to redox processes taking place within the biofilm. The detection of U(V) in a living multispecies biofilm was interpreted as a short-lived intermediate of the U(VI) to U(IV) redox reaction. The presence of U(V) clearly shows that the U(VI) reduction is not a two electron step but that only one electron is involved.
LIFS was also applied to study the alteration of a depleted uranium (DU) disk in contact with synthetic pore water. The pore water used was a calcium phosphate solution (2.5 × 10-3 M Ca, 1 × 10-3 M P) and should mimic fertilized agricultural soil. The storage of the DU disk in calcium phosphate solution for 12 month led to the formation of a thin film of a secondary uranium mineral on the metallic DU. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was applied to spectroscopically characterise the reaction product. TRLFS provided its unequivocal identification as meta-autunite based on the positions of the fluorescence emission maxima at 487.8, 502.0, 523.6, 547.0, 572.1, and 600.6 nm and fluorescence lifetimes of 410 ± 15 and 3300 ± 310 ns. These results highlight the enhanced performance and sensitivity of the TRLFS technique for mineralogical characterization of thin surface films. Furthermore, they demonstrate that the dissolution of uranium from DU projectiles under the conditions described here is limited by the development and solubility of a meta-autunite secondary phase.

  • Invited lecture (Conferences)
    15. Tagung Festkoerperanalytik, 12.-16.07.09, Chemnitz, Deutschland

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Publ.-Id: 13031