Probing the Biogeochemical Behavior of Technetium Using a Novel Nuclear Imaging Approach

作者：Lear Gavin; McBeth Joyce M; Boothman Christopher; Gunning Darren J; Ellis Beverly L; Lawson Richard S; Morris Katherine; Burke Ian T; Bryan Nicholas D; Brown Andrew P; Livens Francis R; Lloyd Jonathan R^*

来源：Environmental Science & Technology, 2010, 44(1): 156-162.

DOI：10.1021/es802885r

Dynamic gamma-camera imaging of radiotracer technetium ((99m)Tc) was used to assess the impact of biostimulation of metal-reducing bacteria on technetium mobility at 10(-12) mol L(-1) concentrations in sediments. Addition of the electron donor acetate was used to stimulate a redox profile in sediment columns, from oxic to Fe(III)-reducing conditions. When (99m)Tc was pumped through the columns, real-time gamma-camera imaging combined with geochemical analyses showed technetium was localized in regions containing biogenic Fe(II). In parallel experiments, electron microscopy with energy-dispersive X-ray (EDX) mapping confirmed sediment-bound Tc was associated with iron, while X-ray absorption spectroscopy (XAS) confirmed reduction of Tc(VII) to poorly soluble Tc(IV). Molecular analyses of microbial communities in these experiments supported a direct link between biogenic Fe(II) accumulation and Tc(VII) reductive precipitation, with Fe(III)-reducing bacteria more abundant in technetium immobilization zones. This offers a novel approach to assessing radionuclide mobility at ultratrace concentrations in real-time biogeochemical experiments, and confirms the effectiveness of biostimulation of Fe(III)-reducing bacteria in immobilizing technetium.

• 出版日期2010-1-1