Premium
Measurement of methane and carbon dioxide fluxes from peatland ecosystems by the conditional‐sampling technique
Author(s) -
Beverland I. J.,
Moncrieff J. B.,
ÓNéill D. H.,
Hargreaves K. J.,
Milne R.
Publication year - 1996
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49712253203
Subject(s) - eddy covariance , flux (metallurgy) , carbon dioxide , atmospheric sciences , methane , environmental science , greenhouse gas , peat , sampling (signal processing) , tracer , flame ionization detector , chemistry , analytical chemistry (journal) , environmental chemistry , physics , ecosystem , gas chromatography , ecology , detector , organic chemistry , chromatography , nuclear physics , optics , biology
The conditional sampling method was used to measure methane (CH 4 ) and carbon dioxide (CO 2 ) fluxes from peatlands in northern Scotland. Preliminary data were obtained using a simple system. Subsequent automation made continuous flux‐measurements possible. Observed CH 4 fluxes were in the range −70 to +110 μmol m −2 h −1 with a mean flux of 23 μmol m −2 h −1 . Peak photosynthetic CO 2 fluxes were in the range −10 to −30 mmol m −2 h −1 . Nocturnal respiration ranged from 0 to +10 mmol m −2 h −1 . The conditional sampling observations showed reasonable agreement with measurements of flux by eddy‐covariance, gradient and aircraft methods. Error analyses and laboratory tests were conducted to determine the precision of the flux‐measurement system. The dominant error was associated with the determination of the mixing‐ratio difference in conditionally‐sampled updraught and downdraught air. The standard error of the difference for CH 4 was typically 0.15 ng g −1 (0.3 parts in 10 9 (p.p.b.)) using a careful high‐repetition sampling strategy with a modified gas chromatographic/flame ionization detector system. Under typical daytime atmospheric conditions this corresponded to a standard error in the flux measurement of 10 μmol m −2 h −1 , which is consistent with field observations. The empirical beta factor in the conditional sampling equation was found to be insensitive to changes in turbulence intensity and atmospheric stability. Simple upscaling models were used to estimate annual carbon‐fluxes to Great Britain's peatlands of −0.5 Mt of carbon in the form of CO 2 and 18 kt in the form of methane.