天然および人工起源メタンの炭素同位体比測定

概要

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We have collected various kinds of gas samples, which are expected to be source of atmospheric methane. Chemical compositions and δ^<13>C values of the gas samples were measured by using a gas chromatograph and a combined gas chromatograph /combustion /isotope ratio mass spectrometer (GC/C/IRMS ) system, respectively. Analytical precision of δ^<13>C value measurement by using GC/C/IRMS system was examined. Overall error of measurement is between 1 ‰ and 2 ‰, estimated from repeated analysis of running standard gas and δ^<13>C variation with the combustion efficiency. Observed δ^<13>C values of the methane vary singificantly from -65.2‰ to -22.9‰, agrees well with data from literatures. Taking into account a positive correlation between ^3He/^4He ratios and δ^<13>C values and a recent trend of atmospheric ^3He/^4He ratio, we discuss contribution of fossil fuel methane to the increase of atmospheric methane.
日本地球化学会の論文
1993-03-02