Microbiological processes sulfate reduction

On the basis of this model, Lovley et al. (17) argued that reductive dissolution of ferric oxides must be a microbiological process because the zone of sulfide generation is distinct from the zone of maximum ferric oxide reduction. Highly eutrophic environments would be an exception. In these systems the zone of decomposition with oxygen as terminal electron acceptor directly overlies the zone of sulfate reduction. 

Figure 6. An idealized scheme for a sedimentary porous medium with pore walls covered by a biofilm. High sulfate reduction rates are maintained even in depths to which sulfate cannot diffuse because of recycling of sulfate within the biofilm. Numbered points (in black circles) denote the following processes I, Respiration consumes oxygen. 2, Microbial reduction of reactive metal Oxides. Reduction of reactive ferric oxides is in equilibrium with reoxidation of ferrous iron by Os. Thus, no net loss of reactive iron takes place in these layers. 3, Microbial reduction of ferric oxides. 4, Sulfate reduction rate (denoted as SRR). 5, Sulfide oxidation, either microbiologically or chemically. 6, Sulfide builds up within the hiofilm, sulfate consumption increases, reactive iron pool decreases. 7, Formation of iron sulfides.

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