Jeon Ong-Hun, Kelly Shelly D, Kemner Kenneth M, Barnett Mark O, Burgos William D, Dempsey Brian A, Roden Eric E
Department of Biological Sciences, The University of Alabama, Tuscaloosa, Alabama 35487-0206, USA.
Environ Sci Technol. 2004 Nov 1;38(21):5649-55. doi: 10.1021/es0496120.
Microbial (Geobacter sulfurreducens) reduction of 0.1 mM U(VI) in the presence of synthetic Fe(III) oxides and natural Fe(III) oxide-containing solids was investigated in pH 6.8 artificial groundwater containing 10 mM NaHCO3. In most experiments, more than 95% of added U(VI) was sorbed to solids, so that U(VI) reduction was governed by reactions at the solid-water interface. The rate and extent of reduction of U(VI) associated with surfaces of synthetic Fe(III) oxides (hydrous ferric oxide, goethite, and hematite) was comparable to that observed during reduction of aqueous U(VI). In contrast, microbial reduction of U(VI) sorbed to several different natural Fe(III) oxide-containing solids was slower and less extensive compared to synthetic Fe(III) oxide systems. Addition of the electron shuttling agent anthraquinone-2,6-disulfonate (AQDS; 0.1 mM) enhanced the rate and extent of both Fe(III) and U(VI) reduction. These findings suggest that AQDS facilitated electron transfer from G. sulfurreducens to U(VI) associated with surface sites atwhich direct enzymatic reduction was kinetically limited. Our results demonstrate that association of U(VI) with diverse surface sites in natural soils and sediments has the potential to limit the rate and extent of microbial U(VI) reduction and thereby modulate the effectiveness of in situ U(VI) bioremediation.
在含有10 mM NaHCO₃的pH 6.8人工地下水中，研究了微生物（硫还原地杆菌）在合成铁（III）氧化物和天然含铁（III）氧化物固体存在下对0.1 mM U(VI)的还原作用。在大多数实验中，超过95%的添加U(VI)吸附到固体上，因此U(VI)的还原受固 - 水界面反应控制。与合成铁（III）氧化物（水合氧化铁、针铁矿和赤铁矿）表面结合的U(VI)的还原速率和程度与水溶液中U(VI)还原过程中观察到的相当。相比之下，与几种不同的天然含铁（III）氧化物固体吸附的U(VI)的微生物还原比合成铁（III）氧化物体系更慢且程度更低。添加电子穿梭剂蒽醌 - 2,⁶ - 二磺酸盐（AQDS；0.1 mM）提高了Fe(III)和U(VI)还原的速率和程度。这些发现表明，AQDS促进了电子从硫还原地杆菌转移到与表面位点结合的U(VI)，在这些位点直接酶促还原在动力学上受到限制。我们的结果表明，U(VI)与天然土壤和沉积物中不同表面位点的结合有可能限制微生物U(VI)还原的速率和程度，从而调节原位U(VI)生物修复的效果。
