Variations of methane stable isotopic values from an Alpine peatland on the eastern Qinghai-Tibetan Plateau

Isotopic signature is a powerful tool to discriminate methane (CH4) source types and constrain regional and global scale CH4 budgets. Peatlands on the Qinghai-Tibetan Plateau are poorly understood about the isotopic signature of CH4 due to the limited experimental conditions. In this study, three campaigns of diurnal air samples spacing 2–3 h were taken from an alpine peatland on the eastern Qinghai-Tibetan Plateau to investigate its source signal characteristics. Both CH4 concentration and its stable carbon isotope (δ13C-CH4) were measured to derive the carbon isotopic signature of the CH4 source using the Keeling plot technique. Diurnal variation patterns in CH4 concentration and δ13C-CH4 were observed during summertime, with depleted δ13C-CH4 signals and high CH4 concentration appearing at nighttime. The δ13C-CH4 signature during summer was calculated to be −71% ± 1.3%, which falls within the range of other wetland studies and close to high-latitude peatlands. The boundary layer dynamic and CH4 source were supposed to influence the measured CH4 concentration and δ13C-CH4. Further investigations of CH4 isotopic signals into the non-growing season are still needed to constrain the δ13C-CH4 signature and its environmental controls in this region.