Evaluational Equipment for Biological Weathering.

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Abstract : Metal sorption and biomineralization largely reflect the availability of dissolved metals in hydrosphere systems. The metal-loaded bacteria has profound implications for the transfer of metals from the hydrosphere to the sediments. Microorganisms will have playd an important role in metal deposition under various temperature conditions. The microorganisms concentrate aqueous dissolved metals onto cell walls and at intracellular sites, during the life cycle, and strongly bind metals during early diagenesis. A sequence is observed in which amorphous cations concentrated at cell walls are progressively transformed to microcrystalline aggregates of carbonate, silicate, Mn-Fe oxides, and clay minerals. The bioprecipitated oxides and oxyhydroxides act as scavengers for heavy metals such as Cu, Pb, Zn, Cd, Sr, and U,in the aqueous toxic-metal dispersion environment. The biomineralization of bacterial cells has been followed in a laboratory simulation by electron microscopy and energy-dispersive X-ray spectroscopy. Several kinds of bacteria were examined for the ability to remove heavy metals from solution. SEM-EDX,TEM,XRF and XRD results indicated that most of metals accumulated at the cell surface as crystalline precipitates after several days of aging.