Coupling of Oxygen and Nitrate to other Redox Pathways

2 Coupling of Oxygen and Nitrate to other Redox Pathways 

For some practical reasons, oxygen is often used as a measure for total respiration of a sediment, mainly in the marine environment (cf. Jahnke et al. 1996 Seiter et al. 2005 Section 12.5.2 Figs. 12.17 - 12.19). Because of all subsequent mineralization processes occurring below, this is of course not strictly correct. Rather a complete net-reoxidation of all reduced species produced during anoxic diagenesis is required - ultimately by means of oxygen (Pamatmat 1971). 

Any fixation and burial of reduced species (e g. the formation of sulfides or carbonates pyrite, siderite.) or the escape of reduced solutes across the sediment-water interface (e.g. CH, NH Np, N, Mtf+, Fe + Bartlett et al. 1987 Seitzinger 1988 Devol 1991 Tebo et al. 1991 Johnson et al. 1992 Thamdrap and Canfield 1996 Wenzhofer et al. 2002) results in an underestimation of the total respiration. The evaluation whether a reoxidation is complete is generally very difficult and is limited by the availability of measurements of all key species. The main questions are (1) How big is the contribution of each pathway compared to the total mineralization (2) To which amount and by which processes are these pathways interrelated Since in most studies a lack of information on certain parameters remains, or different methods are applied to determine one pathway (e.g. differences resulting from in situ / ex situ determination of a species, or different methods to determine for example denitrification and sulfate reduction rates see Section 6.4), the conclusion remains at least to some extent arbitrary. Reimers et al. 

The Role of Oxygen, Nitrate and Phosphorus in Marine Sediments 

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