[1] We measured the escape of methane-containing gas bubbles to the water table in two microhabitats (muddy hollows and Sphagnum-plus-sedge lawns) in a raised bog in West Wales, typical of many northern peatlands. Our study was unusual in its degree of replication (14 gas traps in each microhabitat). Seasonally integrated bubble loss of CH 4 to the water table did not differ significantly between microhabitats. After applying an oxidation correction to give CH 4 fluxes to the atmosphere, the microhabitats still did not differ. Our results suggest that ebullition is an important mechanism of CH 4 loss to the atmosphere, with mean summer rates of 11.7 mg CH 4 m À2 d À1 (muddy hollows) and 6.8 mg CH 4 m À2 d À1 (Sphagnum-plus-sedge lawns). Our data show that the process is spatially and temporally very variable, and that the small sample sizes of many studies (e.g., n = 5) may lead to considerable errors in flux estimation. Citation: Stamp, I., A. J. Baird, and C. M. Heppell (2013), The importance of ebullition as a mechanism of methane (CH 4 ) loss to the atmosphere in a northern peatland,
Peatlands are important sources of atmospheric CH 4 , a potent greenhouse gas. Identifying the controls on CH 4 flux from peatlands requires detailed investigation of fluxes at small scales (the microform scale) where flux chambers are best deployed for measurement. Using chambers presents challenges, not least that of how the CH 4 concentration in chamber gas should be measured. Current field approaches usually involve either (i) online measurement with a flow-through laser absorption spectroscopy instrument or (ii) online or offline analysis of CH 4 by gas chromatography-flame ionization detector (GC-FID) analysis. Online measurement restricts the number of chambers that can be monitored to c. 10 and their spatial spread to a distance of 10-20 m from the CH 4 analyser and is not suited to large-scale studies. GC-FID may present logistical difficulties when conducting research at remote sites because of the need for frequent calibration and, hence, calibration gases. Generally, it is not suited to non-laboratory applications. An alternative is to analyse syringe samples of chamber gas near the field site using a modified laser spectroscopy instrument. We show how such a modification may be made. The theory of our modification is presented, as are the results obtained using it. It is shown that the instrument with the modification compares favourably with GC-FID and can be used near remote field sites in the absence of laboratory facilities. We present flux data from a peatland in Wales, where the flux-chamber CH 4 concentrations were obtained using the modified instrument.
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