Radiocarbon dating of methane and carbon dioxide evaded from a temperate peatland stream

Citation

Garnett MH, Hardie SML, Murray C & Billett M (2013) Radiocarbon dating of methane and carbon dioxide evaded from a temperate peatland stream. Biogeochemistry, 114 (1-3), pp. 213-223. https://doi.org/10.1007/s10533-012-9804-2

Abstract
Streams draining peatlands export large quantities of carbon in different chemical forms and are an important part of the carbon cycle. Radiocarbon (14C) analysis/dating provides unique information on the source and rate that carbon is cycled through ecosystems, as has recently been demonstrated at the air-water interface through analysis of carbon dioxide (CO2) lost from peatland streams by evasion (degassing). Peatland streams also have the potential to release large amounts of methane (CH4) and, though 14C analysis of CH4 emitted by ebullition (bubbling) has been previously reported, diffusive emissions have not. We describe methods that enable the 14C analysis of CH4 evaded from peatland streams. Using these methods, we investigated the 14C age and stable carbon isotope composition of both CH4 and CO2 evaded from a small peatland stream draining a temperate raised mire. Methane was aged between 1617 and 1987 years BP, and was much older than CO2 which had an age range of 303-521 years BP. Isotope mass balance modelling of the results indicated that the CO2 and CH4 evaded from the stream were derived from different source areas, with most evaded CO2 originating from younger layers located nearer the peat surface compared to CH4. The study demonstrates the insight that can be gained into peatland carbon cycling from a methodological development which enables dual isotope (14C and 13C) analysis of both CH4 and CO2 collected at the same time and in the same way.

Keywords
Radiocarbon; Methane; Carbon dioxide; Peatland; Evasion

Journal
Biogeochemistry: Volume 114, Issue 1-3