Mediated mineralization, biogenic

This has been whimsically described as the Great Particle Conspiracy. An important set of these processes involves the incorporation of trace metals into biogenic hard and soft parts. Another involves the adsorption of metals onto the surfaces of particles. Although some metals can theoretically be removed by abiotic precipitation into mineral phases, continuing research confirms that most of the trace metal removal is biologically mediated. 

Reduction of nitro aromatic compounds often appears to be a two-step process, in which a mediator is required for facile transfer of electrons from a bulk reductant to the contaminant. A well documented example is the coupling of organic matter oxidation by iron reducing bacteria to "abiotic" nitro reduction by biogenic Fe(II) that is adsorbed to mineral surfaces in a column containing aquifer material (36, 39, 76). 

Thus, it appears that in situ immobilization of toxic metals and radionuclides by microbial reduction is a plausible pathway for contaminant stabilization (Lov-ley Phillips, 1992) however, mineral surfaces and the production of biogenic materials may dictate the effectiveness of bacterially mediated metal-reduction processes or the operating mechanism (Tripathi, 1984 Hsi Langmuir, 1985 Zachara et al., 1989 Mesuere Fish, 1992 Kent et al., 1994, 1995 Chisholm-Brause et al., 1994 McKinley et al., 1995 Weng et al., 1996). Thus, there exists a need to study the intricate coupling of microbiological and geochemical processes on contaminant reduction. 

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