Rapid assay for microbially reducible ferric iron in aquatic sediments

Applied and Environmental Microbiology
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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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Publication type Article
Publication Subtype Journal Article
Title Rapid assay for microbially reducible ferric iron in aquatic sediments
Series title Applied and Environmental Microbiology
DOI 10.1128/aem.53.7.1536-1540.1987
Volume 53
Issue 7
Year Published 1987
Language English
Publisher American Society for Microbiology
Contributing office(s) Toxic Substances Hydrology Program
Description 5 p.
First page 1536
Last page 1540
Country United States
Other Geospatial Potomac River estuary
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