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Modelluntersuchungen zum Mechanismus der bakteriellen Eisenreduktion in Hydromorphen Böden

1977; Wiley; Volume: 140; Issue: 5 Linguagem: Inglês

10.1002/jpln.19771400508

0044-3263

J. C. Munch, J. C. G. Ottow,

Mine drainage and remediation techniques

Model experiments on the mechanism of bacterial iron‐reduction in water‐logged soils In model experiments, iron‐reduction with Bacillus polymyxa (nit + ) and Clostridium butyricum (nit − ) was followed in relation to the development of pH, Eh and glucose fermentation. In parallel tubes, the influence of NO, (KNO,) and/or Mn02‐Powder (Merck) on Fe(I1) formation and rH (calculated from pH and Eh) was measured. All tubes were incubated anaerobically (N2/C02 = 9/1) at 30°C. Both with Bacilluspolymyxa (nit + ) as well as with Clostridium butyricum (nit − ), the reduction‐intensity rH decreased rapidly reaching entirely reducing conditions (rH = 0) within 2–3 days. In both cases iron‐reduction and glucose utilization developed sigmoidal and miror symmetrically (Fig. 1) In the case of B. polymyxa (nit + ) the addition of NO, and/or Mn02 suppressed iron‐reduction nearly entirely. With C. butyricum, only Mn02 (but not nitrate) affected iron‐reduction significantly. Nitrate remained unchanged throughout the incubation period, although completely reducing conditions (rH = 0) were obtained (Fig. 2). Apparently, nitrate, Mn02 or Fe203 are reduced directly and specifically rather than indirectly as a consequence of reducing metabolites and/or by a lowered redox potential in the environment. If nitrate, Mn02 and Fe203 are reduced chemically by reducing condition, the reduction sequence nitrate → Mn(1V)‐oxides → Fe(II1)‐oxides should occur in relation to pH and Eh (rH) and independently of the type of organism (nit + or nit − ) in question. This view is rejected by the results presented. With nit + bacteria such as B. polymyxa, the enzyme nitrate reductase seems to act as one mechanism of iron‐ and manganese‐reduction. However, with C. butyricum (nit − ), another, so far unknown enzym system (ferrireductase?), should be made responsible for iron‐ and manganese‐reduction.