Carbon isotopes in peat, DOC, CO2, and CH4 in a holocene peatland on Dartmoor, southwest England

Carbon gases with younger C-14 ages than those of the surrounding peat have been reported from continental boreal peatlands, a fact which suggests tha t significant movement of CO2, CH4, or DOC (dissolved organic carbon) and e xport of C via subsurface processes are not accounted for in most estimates of contributions to the C cycle. This paper tests the hypothesis that simi lar processes can occur in oceanic ombrotrophic mires where water and gas m ovement is theoretically minimal. Measurements of C-14 and delta(13)C in CO 2, CH4, and DOC, and of tritium, are reported from depths to 250 cm at Tor Royal, a raised mire in southwest England. Radiocarbon ages of gases are 14 60 to 500 yr younger than those of peat from the same depths, and CO2 is co nsistently younger than CH4. DOC is 1260 to 830 yr younger than the peat, a nd significant amounts of tritium were found at all depths, Gas ages are mo stly intermediate between the age of the peat and that of the DOC, which su ggests that C is principally transported as DOC. However, some gases are yo unger than their associated DOG, which implies that movement of dissolved g ases may also take place. delta(13)C values in gases suggest that CO2 reduc tion is the major pathway for CH4 production. Transport of C in deep peats is likely to be a significant component in the overall C budget of ombrotro phic oceanic peatlands, and C export via discharge to ground or surface wat ers may be an important mechanism for gaseous C emissions.