Effect of temperature and atmospheric pressure on methane (CH4) ebullition from near-surface peats

Recent studies suggest that ebullition of biogenic gas bubbles is an important process of CH4 transfer from northern peatlands into the atmosphere and, as such, needs to be better described by models of peat carbon dynamics. We develop and test a simple ebullition model in which a threshold gas volume in the peat has to be exceeded before ebullition occurs. The model assumes that the gas volume varies because of gas production and variations in pressure and temperature. We incubated peat cores in the laboratory for 190 days and measured their volumetric gas contents and the ebullition flux. The laboratory results support the threshold concept and, considering the simplicity of the model, the calculated ebullition compared well with measured fluxes during the final 120 days with an r(2) of 0.66. An improved, more realistic description would also include temporal and spatial variations in gas production and bubble retention terms.