Redox Properties of Peat Particulate Organic Matter: Quantification of Electron Accepting Capacities and Assessment of Electron Transfer Reversibility

Peat particulate organic matter (POM) has been hypothesized to act as a terminal electron acceptor (TEA) for anaerobic microbial respiration in northern peatlands, thereby lowering dissolved methane (CH4) concentrations these systems. However, the redox properties of peat POM and an assessment its state situ remain missing, mainly due lack accurate analytical approach quantify number electrons that are transferred to/from POM. Here, we first developed new spectrophotometric method transferable POM—denoted hereafter accepting capacity (EAC)—by reacting with reduced species probe compound 4,4’-bipyridinium-1,1'bis(2-ethylsulfonate). Second, used this EAC oxidized reference material (0.38 ± 0.039 mmol e?/g POM) redox-preserved from three ombrotrophic bogs Värmland, Sweden (0.17–0.24 POM). These values substantially higher than previous estimates, likely reflecting kinetic artifacts methods. We further established reversible transfer oxic over cycle electrochemical reduction O2 re-oxidation. Finally, determined two bog samples were collected anoxically (i.e., state-preserved increased by ?0.09 upon exposure air 8 days, demonstrating was indeed situ. Collectively, our results strongly support acts sustainable TEA which may lower release