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Appl Environ Microbiol. 1987 July; 53(7): 1536–1540.
PMCID: PMC203906

Rapid Assay for Microbially Reducible Ferric Iron in Aquatic Sediments

Abstract

The availability of ferric iron for microbial reduction as directly determined by the activity of iron-reducing organisms was compared with its availability as determined by a newly developed chemical assay for microbially reducible iron. The chemical assay was based on the reduction of poorly crystalline ferric iron by hydroxylamine under acidic conditions. There was a strong correlation between the extent to which hydroxylamine could reduce various synthetic ferric iron forms and the susceptibility of the iron to microbial reduction in an enrichment culture of iron-reducing organisms. When sediments that contained hydroxylamine-reducible ferric iron were incubated under anaerobic conditions, ferrous iron accumulated as the concentration of hydroxylamine-reducible ferric iron declined over time. Ferrous iron production stopped as soon as the hydroxylamine-reducible ferric iron was depleted. In anaerobic incubations of reduced sediments that did not contain hydroxylamine-reducible ferric iron, there was no microbial iron reduction, even though the sediments contained high concentrations of oxalate-extractable ferric iron. A correspondence between the presence of hydroxylamine-reducible ferric iron and the extent of ferric iron reduction in anaerobic incubations was observed in sediments from an aquifer and in fresh- and brackish-water sediments from the Potomac River estuary. The assay is a significant improvement over previously described procedures for the determination of hydroxylamine-reducible ferric iron because it provides a correction for the high concentrations of solid ferrous iron which may also be extracted from sediments with acid. This is a rapid, simple technique to determine whether ferric iron is available for microbial reduction.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Lovley DR, Phillips EJ. Organic matter mineralization with reduction of ferric iron in anaerobic sediments. Appl Environ Microbiol. 1986 Apr;51(4):683–689. [PMC free article] [PubMed]
  • Lovley DR, Phillips EJ. Availability of ferric iron for microbial reduction in bottom sediments of the freshwater tidal potomac river. Appl Environ Microbiol. 1986 Oct;52(4):751–757. [PMC free article] [PubMed]
  • Sørensen J. Reduction of ferric iron in anaerobic, marine sediment and interaction with reduction of nitrate and sulfate. Appl Environ Microbiol. 1982 Feb;43(2):319–324. [PMC free article] [PubMed]

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