An ombrotrophic bog as a methane reservoir

Abstract

The distribution of methane in an ombrotrophic bog was examined by extracting the gas from different depths, using evacuated bottles and sampling tubes. Methane was extracted during 75 min, from 60 cm, 90 cm and 120 cm depths at 25 stations in a 24 meter‐square area. The amount of methane extracted varied widely between samples, and this variation was greater within each depth than between the different depths. Approximately two and a half times as much methane was found at 90 cm and 120 cm depths as at 60 cm. The amount of methane from sites more than 60 cm below the surface can be correlated with the methane microbially produced from peat from the same site during laboratory incubations. Much less methane could be extracted from near‐surface peat than from deeper levels, but laboratory incubations of peat from this level produced 10‐fold more methane. Our results show that there is a considerable amount of methane trapped below 50 cm depth within an ombrotrophic bog, which we calculate in the bog studied to be 1.7 Gg. We suggest this entrapped methane reduces the hydraulic conductivity in the lower layers of the peat by blocking the soil pore spaces and preventing fluid movement; this in turn generates an elevated water table allowing the formation of a raised bog. We further suggest that if this peat is disturbed by mining or farming, the entrapped methane could be released into the atmosphere and add to the atmospheric pollution by greenhouse gases.

Pressure variations in peat as a result of gas bubble dynamics

“…It has long been known that methane gas bubbles are abundant in deeper peat (Brown et al, 1989;Romanowicz et al, 1993Romanowicz et al, , 1995, although the dynamics of gas bubbles and the magnitude of the excess pressure they cause is poorly understood. Recently, Rosenberry et al (2003) revealed a consistent overpressure of 3-35 cm water height at 2 m depth in a bog.…”

Depth distribution of microbial production and oxidation of methane in northern boreal peatlands

“…However, the extent to which lower production rates in comparatively dry environments also contribute to this general pattern is not known. Although the depth distribution and rate of methane production in Sphagnumdominated peatlands have been reported [4,24,41,43,47,48,51], the relation between methane production and the depth of the water table has not been well characterized.…”

Carbon Isotopic Composition of Deep Carbon Gases in an Ombrogenous Peatland, Northwestern Ontario, Canada

“…Recent studies do not support the first hypothesis. They show deeper peat layers more highly saturated with methane than peat layers closer to the surface (Dinel et al 1988;Brown, Mathur & Kushner 1989;Claricoates 1990;Buttler et a1.1991). In either case, the gas ages represent an average estimate of the ages of carbon sources used in gas production.…”

“…et al 1988;Brown, Mathur & Kushner 1989;Claricoates 1990;Mathur, Dine! & Levesque 1991;Buttler et al 1991;Romanowics, Siegel & Glaser 1991), but the ultimate fate of these deep gases remains a mystery.…”