Williamson Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, M13 9PL, UK.
Environ Sci Technol. 2010 Jan 1;44(1):156-62. 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.
放射性示踪剂锝（(99m)Tc）的动态伽马相机成像用于评估在沉积物中 10(-12) mol L(-1)浓度下，生物刺激金属还原菌对锝迁移性的影响。添加电子供体乙酸盐用于刺激沉积物柱中的氧化还原剖面，从好氧到 Fe(III)还原条件。当 (99m)Tc 通过柱泵送时，实时伽马相机成像与地球化学分析相结合表明锝被定位在含有生物成因 Fe(II)的区域中。在平行实验中，电子显微镜与能量色散 X 射线（EDX）映射证实了沉淀在沉积物中的 Tc 与铁有关，而 X 射线吸收光谱（XAS）证实 Tc(VII)被还原为难溶的 Tc(IV)。这些实验中微生物群落的分子分析支持生物成因 Fe(II)积累与 Tc(VII)还原沉淀之间的直接联系，在锝固定区中 Fe(III)还原菌更为丰富。这为在实时生物地球化学实验中评估超痕量浓度放射性核素的迁移性提供了一种新方法，并证实了生物刺激 Fe(III)还原菌固定锝的有效性。
