Авторы: Ruby C., Upadhyay C., Gehin A.

2006 г.

Envir.Sci.Techn.

Bacterial activity is commonly thought to be directly responsible for denitrification in soils and groundwater. However, nitrate reduction in low organic sediments occurs abiotically by FeII ions within the fougerite mineral (IMA 2003- 057), giving the bluish-green color of gleysols. Fougerite, the mineral counterpart of FeII-III oxyhydroxycarbonate, FeII _6(1-x)FeIII _6xO₁₂H_2(7-3x)CO₃, provides a unique in situ redox flexibility, which can adapt x ) {[FeIII]/[Fetotal]} between 1/3 and 2/3 as shown using Mo¨ssbauer spectroscopy. Chemical potential and Eh-pH diagrams for this system were determined from electrode potential monitored during deprotonation of hydroxycarbonate FeII 4FeIII 2(OH)12CO₃ to assess the possibility of reducing pollutants in the field. Bioreduction of ferric oxyhydroxides in anoxic groundwater yields dissolved FeII, whereas HCO₃^- anions produced from organic matter are incorporated into fougerite layered double oxyhydroxide structure. Thus, fougerite is the solidstate redox mediator acting as electron shuttle that helps bacterial activity for reducing nitrate by coupling dissimilatory FeIII reduction and oxidation of FeII with reduction of NO₃^-. It is proposed that this system could be used in the remediation of soils and nitrified waters.

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