Stable isotope ratios of the atmospheric CH4, CO2 and N2O in Tokai-mura

This report presents the results and interpretation of stable isotope ratios of the atmospheric CH4, CO2 and N2O from a variety of sources in Tokai-mura. The seasonal changes of δ13CH4, δ13CO2 and δ15N2O were determined under in-situ conditions in four sampling sites and one control site. Such measurements are expected to provide a useful means of estimating the transport mechanisms of the three trace gases in the environment. These isotopic signatures were analyzed by Isotope Ratio Mass Spectrometer (IRMS, Micromass Isoprime). Our data showed the significant seasonal fluctuation in the Hosoura rice paddy during the entire growing season in 1999. Possible causes for the variation are postulated. Additional measurements on soil properties and on organic δ13C in rice plant are suggested. Cited outstanding original papers are summarized in the references. (author)