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Seasonal variations in stable carbon and hydrogen isotope ratios in methane from rice fields
Author(s) -
Marik Thomas,
Fischer Horst,
Conen Franz,
Smith Keith
Publication year - 2002
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 - 10.1029/2001gb001428
Subject(s) - methane , atmospheric methane , paddy field , δ13c , stable isotope ratio , growing season , atmosphere (unit) , environmental chemistry , environmental science , mass spectrometry , carbon cycle , atmospheric sciences , carbon dioxide , chemistry , carbon fibers , seasonality , materials science , meteorology , ecology , geology , ecosystem , physics , organic chemistry , chromatography , quantum mechanics , composite number , composite material , biology
During two successive growing seasons, methane emissions from rice fields in Italy were measured. High‐precision measurements of the methane 13 C/ 12 C and D/H ratios were carried out by mass spectrometry and tunable diode laser absorption spectrometry. Significant seasonal variations were found for both δ 13 C and δD. The results confirm earlier observations by Bergamaschi [1997] in finding a seasonal cycle with isotopically depleted methane in the main growing season and higher values at the beginning and the end of the season during drainage of the field. The measured δ 13 C diurnal cycles showed a strong correlation with the methane emission rate. The isotopic composition of methane, which depended on the season, can be explained by variations of the different pathways for methane production, oxidation, and release into the atmosphere. A model based on these parameters was able to reproduce the field measurements and indicate the principal causes of observed fluctuations in the isotopic methane composition.