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Enigmatic stable isotope dynamics of deep peat methane
Author(s) -
Waldron Susan,
Hall Allan J.,
Fallick Anthony E.
Publication year - 1999
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/1998gb900002
Subject(s) - peat , methane , flux (metallurgy) , bog , carbon dioxide , atmosphere (unit) , isotopes of carbon , stable isotope ratio , environmental chemistry , carbon fibers , substrate (aquarium) , anaerobic oxidation of methane , geology , carbon cycle , methanogenesis , chemistry , mineralogy , total organic carbon , materials science , oceanography , ecology , physics , organic chemistry , quantum mechanics , ecosystem , composite number , composite material , biology , thermodynamics
The carbon and hydrogen stable isotope ratios of methane and carbon dioxide from Ellergower Moss, a raised peat bog in SW Scotland, were measured to characterize the isotopic composition of peatland gas flux that is not subject to near‐surface bacterial oxidation. Two profiles of gas samples, collected in situ under pools at 1 m intervals from the surface to a depth of 5 m, gave mean isotopic signatures of δ 13 C(CH 4 ) = −76±3‰ ( n =22), δ 13 C(CO 2 ) =3.8±5.3‰ ( n =22), and δD(CH 4 ) = −294±39‰ ( n =21). The profiles revealed two isotopically distinct methane reservoirs within Ellergower Moss, with a boundary layer at 2–2.5 m. The zonation appears to be independent of methanogenic pathway and of changes in δ 13 C or δD of bulk substrate, but there is a positive correlation between an increase in δD(CH 4 ) and reported increasing partial pressure of methane with depth ( r = 0.943 and n = 18, >99.9% significant). To reflect C and H cycling within the peat and gas storage mechanisms, we propose the zones can be termed dynamic (0–2 m) and static (from 3–5 m). The δD(CH 4 ) profiles exhibit the zonation and boundary most clearly, with a 52±18‰ difference between methane in the dynamic zone (−332±17‰) and that in the static zone (−260±9‰). Only if the static zone is breached, will its methane be released to the atmosphere; thus unoxidized peatland flux to the atmosphere will be similar in composition to that produced in the dynamic reservoir, where δ 13 C(CH 4 ) = −76±4‰ and δD(CH 4 ) = −332±17‰.