z-logo
Premium
Contributions of natural and anthropogenic sources to atmospheric methane variations over western Siberia estimated from its carbon and hydrogen isotopes
Author(s) -
Umezawa Taku,
Machida Toshinobu,
Aoki Shuji,
Nakazawa Takakiyo
Publication year - 2012
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 - 10.1029/2011gb004232
Subject(s) - isotopes of carbon , wetland , seasonality , environmental science , methane , atmospheric sciences , atmospheric methane , stable isotope ratio , δ13c , isotope analysis , carbon fibers , environmental chemistry , isotope , hydrogen , chemistry , geology , total organic carbon , oceanography , ecology , physics , materials science , organic chemistry , quantum mechanics , composite number , composite material , biology
Aircraft measurements of carbon and hydrogen isotopic ratios of atmospheric CH 4 ( δ 13 CH 4 and δ D‐CH 4 ), with the respective precisions of 0.08‰ and 2.2‰, as well as CH 4 concentration were made at 1 and 2 km altitudes over western Siberia during 2006–2009. δ 13 CH 4 and δ D‐CH 4 were almost always lower at lower altitudes, while the CH 4 concentration was higher, implying strong sources on the ground with low isotopic values. δ 13 CH 4 showed a clear seasonal minimum in the late summer, while seasonality of CH 4 and δ D‐CH 4 was ambiguous due to the local disturbances. By inspecting the relationships between the CH 4 concentration and isotopes, we found that isotopic source signatures in the winter (December–April) are −41.2 ± 1.8 and −187 ± 18‰ for δ 13 CH 4 and δ D‐CH 4 , respectively, and the corresponding values in the summer (June–October) are −65.0 ± 2.5 and −282 ± 25‰. These values indicate predominant CH 4 emissions from fossil fuel facilities in the winter and wetlands in the summer. It was also found that the shorter‐term CH 4 variations are more influenced by fossil CH 4 than that from wetlands. The finding presumably reflects the fact that the former is released from limited areas such as leakage from fossil fuel facilities, while the latter is released from a vast expanse of wetland. By employing a CH 4 emission data set used in an atmospheric chemistry transport model, we calculated seasonal isotopic changes of CH 4 sources in western Siberia and compared them to the estimates obtained in this study. The results indicated that the seasonal change in the CH 4 emission data set is reasonable, at least in terms of a ratio of fossil to biogenic emissions.

This content is not available in your region!

Continue researching here.

Having issues? You can contact us here