Minireview: The Potential of Enhanced Manganese Redox Cycling for Sediment Oxidation

Abstract

Both natural and anthropogenic processes are responsible for excessive organic loading of submerged soils, with detrimental environmental consequences. The often insufficient natural attenuation can be enhanced by exploiting microbial manganese cycles. This review describes how an anoxic oxidation of organic matter with concomitant reduction of MnO ₂ can link up with a reoxidation of the resulting, soluble Mn(II) in oxic layers. The potentially attainable oxidation rates through these natural cycles are of the same order as the organic carbon accumulation rates. The microbiology and physiology of the responsible organisms are discussed, as well as examples of naturally occurring manganese cycles and the possibility to engineer this natural phenomenon.

Keywords:

• sediment
• organic matter
• oxidation
• manganese
• cycle
• redox

ACKNOWLEDGMENTS

Liesje De Schamphelaire is supported through a PhD grant from the Bijzonder Onderzoeks Fonds of Ghent University (Grant no. 01D24405). The useful comments of Peter Clauwaert, Ilse Forrez, Bram Pauwels and Robin Temmerman were highly appreciated.

Current address for Korneel Rabaey: The Advanced Wastewater Management Centre, University of Queensland, St Lucia, QLD 4072, Australia.

Notes

^a Gibbs free energy changes are based on the Redfield molecule (CH₂O)₁₀₆(NH₃)₁₆(H₃PO₄), but are presented for one glucose molecule, being 6/106 of the Redfield molecule. Redox reactions and Gibbs free energy changes are adopted from Froelich et al. (1979), except for the reaction with Fe(OH)₃, where the value is calculated based on Froelich et al. (1979) and Stumm and Morgan (1996).

^b Values are at standard conditions (1 M and 25°C) and pH 7.

^c Redox potentials for the reduction half reactions are calculated according to Stumm and Morgan (1996).