Water Resources Division, U.S. Geological Survey, Reston, Virginia 22092.
Appl Environ Microbiol. 1987 Jul;53(7):1536-40. doi: 10.1128/aem.53.7.1536-1540.1987.
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.
可被微生物还原的铁的可用性可通过铁还原菌的活性直接测定，也可通过新开发的用于测定微生物可还原铁的化学方法来测定。该化学方法基于在酸性条件下，通过羟胺还原非晶质的三价铁。羟胺能够还原各种合成的三价铁形式的程度与铁在铁还原菌的富集培养物中被微生物还原的敏感性之间存在很强的相关性。当含有可被羟胺还原的三价铁的沉积物在厌氧条件下孵育时，随着时间的推移，可被羟胺还原的三价铁浓度下降，亚铁铁不断积累。一旦可被羟胺还原的三价铁耗尽，亚铁铁的产生就停止了。在不含可被羟胺还原的三价铁的还原沉积物的厌氧孵育中，即使沉积物中含有高浓度的草酸盐可提取的三价铁，也没有微生物铁还原。在含水层沉积物以及波托马克河口的淡水和微咸水沉积物中，可观察到在厌氧孵育中存在可被羟胺还原的三价铁与三价铁还原程度之间的对应关系。与以前描述的测定羟胺可还原铁的程序相比，该方法有了显著的改进，因为它提供了一个对也可能用酸从沉积物中提取的高浓度固体亚铁铁的校正。这是一种快速、简单的技术，可用于确定三价铁是否可用于微生物还原。
