Michael F. Billett and Frank Harvey
Proceedings of the 14th International Peat Congress
carbon-dioxide, dissolved-organic-carbon, evasion, flux, methane
Billett, Harvey 2012: How Important is the Evasion Flux Term in the Carbon and GHG Balance of Peatlands?
Theme X. Peatland carbon budgets and greenhouse gas (GHG) fluxes
Instantaneous measurements of gas exchange from flowing surface waters in six UK peatland sites show that the CO2 evasion rate per unit area of surface water (median 133, mean 367 μg C m-2 s-1) is more than a magnitude higher than the CH4 evasion rate (median 0.22, mean 1.45 μg C m-2 s-1). Scaling to the whole catchment, using measurements of water surface area (0.07-0.41%) we show that the CO2 evasion flux is a significant component of the aquatic C flux and regularly exceeds the downstream DOC flux, typically 10-25 g C m-2 yr-1 in most peatland catchments. We conclude that whilst the CO2 evasion flux is highly variable and difficult to quantify at the catchment scale, it is a significant flux term in the carbon balance of many peatland landscapes, strongly controlled by hydrological extremes. Excluding aquatic CO2 evasion from calculations of carbon balance may therefore lead to an overestimation of the sink strength of peatland systems.