Bacterial Reduction of Iron in Clay Minerals

这是一项关于粘土矿物中结构铁（Fe）的细菌还原的跨学科研究。细菌和铝硅酸盐粘土矿物是土壤和水生沉积物中最丰富和最具化学活性的两种成分。两者都被独立地确定为决定退化率的主要参与者。有毒金属和有机污染物在环境中的积累和迁移；但人们对它们的相互作用机制、如何影响它们的行为以及利用细菌-粘土反应在自然环境系统中实现最佳性能的潜力知之甚少。铁在粘土晶体结构中的氧化和还原（静电电荷的变化）是一种潜在的非常重要的相互作用，但很少引起人们的注意。在实验室中使用无机还原剂的研究表明，铁氧化态的变化深刻地改变了粘土的化学和物理行为。当粘土和细菌相互作用时，环境中也会发生同样的事情吗？如果是这样，程度和速度如何？在与粘土的氧化还原过程中，细菌是否会改变其他化合物，如金属和有机酸？最佳条件是什么？因此，本研究的总体目标将是双重的：(1)确定土壤和沉积物中细菌减少的最佳条件；(2)确定细菌还原对粘土性质以及粘土-有机和粘土-金属相互作用的影响。

9523902 Stucki This is an interdisciplinary study of the bacterial reduction of structural iron (Fe) in clay minerals. Bacteria and alumino-silicate clay minerals are two of the most abundant and most chemically active constituents of soils and aquatic sediments. Both have been independently identified as major players in determining the rates of degradation., accumulation, and transport of toxic metals and organic pollutants in the environment; but little is known about their interaction mechanism(s), how this affects their behavior, and the potential for exploiting bacterial-clay reactions to achieve optimal performance in natural environmental systems. Oxidation and reduction (change of electrostatic charge) of Fe in the clay crystal structure is one type of interaction that potentially is of very great significance, but little attention has been given to it. Studies using inorganic reducing agents in the laboratory revealed that changes in Fe oxidation state profoundly alter the chemical and physical behavior of the clay. Does the same thing happen in the environment when clays and bacteria interact? If so, to what extent and at what rate? Does the bacteria alter other compounds, such as metals and organic acids, during the oxidation-reduction process with clays? What are the optimum conditions? The overall goals of this study will, therefore, be two-fold: (1) to identify the optimum conditions under which bacteria reduction will occur in soils and sediments; and (2) to determine the effect of bacterial reduction on clay properties and on clay-organic and clay-metal interactions.