Ebullition of methane-containing gas bubbles from near-surface Sphagnum peat

Abstract

To date, very little information has been available on the build-up and release of biogenic gas bubbles in poorly-decomposed bog peats near the peatland surface (upper 1 m). We investigated the importance of ebullition of biogenic gas bubbles as a mechanism for the transport of CH4 to the atmosphere in eight cores (24 cm diameter, 22 cm depth) of poorly-decomposed, near-surface bog peat. Ebullition was recorded in all but one sample but varied greatly between samples. Maximum rates of CH4 efflux via ebullition were also highly variable, ranging from 2.2 to 83.0 mg CH4 m-2 day -1. These rates are similar to rates of diffusive CH 4 efflux. Our results also show that wetland methane models are likely to need revision because they assume that unrealistically high CH4 porewater concentrations are required before bubbles can be produced and because, in part, they do not account for gas bubble build-up prior to ebullition. Copyright 2004 by the American Geophysical Union.