Nitrate contamination in soils, sediments, and aquifers is a significant and widespread issue. A complete understanding of all nitrate degradation processes in these environments, especially in clay mineral-rich soils, is still lacking. The objective of this study was to study the potential of removing nitrate contaminant using structural Fe(II) in clay mineral nontronite (NAu-2). Specifically, the coupled processes of microbial oxidation of Fe(II) in microbially reduced NAu-2 and nitrate reduction by Pseudogulbenkiania species strain 2002 was investigated. Bio-oxidation experiments were conducted in bicarbonate-buffered medium under both growth and non-growth conditions. The extents of Fe(II) oxidation and nitrate reduction were measured by wet chemical methods. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and 57Fe-M�ssbauer spectroscopy were used to observe mineralogical changes associated with Fe(III) reduction and Fe(II) oxidation in nontronite. The results showed that the bio-oxidation extent under growth and non-growth conditions reached 93% and 57%, respectively. Over the same time period, nitrate was completely reduced under both conditions to nitrogen gas (N2), via an intermediate product nitrite. Magnetite was a mineral product of nitrate�dependent Fe(II) oxidation, as evidenced by XRD data and TEM diffraction patterns. The results of this study highlight the significance of iron-bearing clay minerals in the global nitrogen cycle, as well as the potential applications in nitrate removal in soils.

Biological oxidation of Fe(II) in microbially reduced nontronite coupled with nitrate reduction

246th National Meeting (2013)

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