Biologically-mediated Manganese Oxide Deposition and its Effects on Trace Metal Cycling in Aquatic Environments

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This award in the Environmental Geochemistry and Biogeochemistry program supports research on trace metal cycling in the environment by Drs. Leonard W. Lion, Michael L. Shuler, and William C. Ghiorse of the Department of Civil and Environmental Engineering, Cornell University. The research is supported by the Divisions of Chemistry and Earth Sciences and the MPS Office of Multidisciplinary Activities. The long term goal is to develop an accurate mechanistic model for predicting formation of biologically-mediated surface coatings and their subsequent influence on transition metal distribution in natural and engineered environments. This project focuses on identifying the role of manganese oxides in controlling transition metal cycling and on developing a quantitative model for the process. In particular, the influence of bacterial processes and biofilm formation on both manganese oxidation and metal binding by manganese oxides will be included in the model. Manganese oxidation and manganese oxide deposition will be measured in cultures of bacteria in a bioflim reactor system where pH, temperature, dissolved oxygen concentration, fluid shear and light intensity can be controlled. Manganese oxide surface properties and adsorption of lead and cadmium for biologically oxidized samples will be compared to results obtained for abiotic chemical redox processes. The result will be an integrated computational model to predict manganese oxidation and manganese oxide trace metal binding, including cellular growth, biofilm accumulation, manganese redox reations, and trace metal speciation and adsorption. Adsoprtion of lead and cadmium to iron and manganese oxide particles is thought to be an important means of transport of these toxic metals in the natural environment. This study is directed toward understanding the role of manganese oxide adsorption, including the role of biologically-mediated manganese oxidation and cycling, in the transport process. The results will also be relevant to development of remediation strategies for toxic metals.