A high-precision measurement system for the carbon isotope ratio of atmospheric CH 4 (δ 13CH 4) was developed using a pre-concentration device for CH 4, and a gas chromatograph-combustion-isotope ratio mass spectrometer (GC-C-IRMS). The measurement system required 100 m/ STP of an atmospheric air sample, corresponding to approximately 0.18 μ l STp of CH 4 to determine the δ 13CH 4 value with a reproducibility of 0.07%o. Replicated analyses of a CH 4-in-air standard gas during the period from 2002 to 2008 indicated that the value of δ BCH 4 measured by this system was consistent within the measurement reproducibility. To evaluate the δ 13CH 4 measurement system, thus developed, diurnal variations of the atmospheric CH 4 concentration and δ 13CH 4 were observed in the northern part of the Tokyo metropolitan area. From the relationship between the CH 4concentration and δ 13CH 4 dominant sources of the observed CH 4 fluctuations were identified.
|Number of pages||8|
|Publication status||Published - 2009 Mar|
ASJC Scopus subject areas
- Aquatic Science
- Earth and Planetary Sciences(all)