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.
