Spatial and temporal variations of dissolved gases (CH4, CO2, and O2) in peat cores

Spatial and temporal variations in the concentrations of dissolved gases (CH4, CO2, and O2) in peat cores were studied using membrane inlet mass spectrometry (MIMS). Variations in vertical gas profiles were observed between random peat cores taken from hollows on the same peat bog. Methane concentrations in profiles (0–30 cm) generally increased with depth and reached maximum values in the range of 200–450 μm CH4 below about 13-cm depth. In some profiles, a peak of dissolved methane was observed at 7-cm depth. Oxygen penetrated to approximately 2-cm depth in the hollows. The sampling probe was used to continuously monitor CH4, CO2, and O2 concentrations at fixed depths in peat cores over periods of several days. The concentration of dissolved CO2 and O2 at 1-cm depth oscillated over a 24-h period with the maximum of CO2 concentration corresponding with the minimum of 02. Diurnal variations in CO2 but not CH4 were measured at 15-cm depth; dissolved CO2 levels decreased during daylight hours to a constant minimum concentration of 4.85 mm. This report also describes the application of MIMS for the measurement of gaseous diffusion rates in peat using an inert gas (argon); the value of D, the diffusion coefficient, was 2.07 × 10−8 m2 s−1.