12th July 2013. A new study published in Environmental Science and Technology has shed light on anaerobic oxidation of methane (AOM) in peatlands. The importance of AOM as a methane sink has been recognised in marine sediments for a number of years, but the process is only poorly understood in peatlands, and has received relatively little attention.
In the latest study, researchers collected soil samples from 15 different peatlands and carried out lab incubation experiments. The addition of 13C-CH4 isotope tracers to the anaerobic incubations resulted in the production of 13CO2 for samples from all 15 peatlands, implying that AOM occurred at all sites. Rates of AOM were sustained for longer in fens compared to bogs, and the authors hypothesised that this was due to groundwater inputs supplying the electron acceptors needed to maintain the process. However, the second part of the experiment that attempted to determine the relevant electron acceptor found that additions of nitrate, sulphate and iron had no effect on AOM. It therefore appears that the pathway of AOM in peatlands is fundamentally different to that in other systems.
As a final piece of work, the authors calculated the amount of methane consumed through AOM for northern peatlands using low, average, and high estimations. The results from their average scenario suggested that AOM could act as a sink of 24 Tg of methane each year; a significant amount. Methane fluxes in peatlands are traditionally modelled using variables such as temperature, vegetation and water table, with methane consumption and production being considered to be oxic and anoxic processes. However, the growing body of research on peatland AOM may well have implications on the use of such simple models.
Reference: Gupta, V., Smemo, K.A., Yavitt, J., Fowle, D.A., Branfireun, B.A., Basiliko, N. 2013. Stable isotopes reveal widespread anaerobic methane oxidation across latitude and peatland type. Environmental Science and Technology, in press. DOI: 10.1021/es400484t