Highly sensitive analysis of geochemical cycles of nitrous oxide and methane through isotope tracers

点击翻译按钮获取中文摘要

(1) Molecules of low concentration but relatively large amount from atmosphere or atmospheric equilibrated water samples have been analyzed on an mass spectrometer equipped with dual inlet systems, and those of high concentration and small amount, from soil gass for example, have been analyzed on a gas chromatograph/combusion/isotope ratio mass spectrometer. In addition to these system, highly sensitive analytical system has been constructed to determine the isotope ratios of molecules of low concentration and very small amount in the present study.Carbon isotope ratios in methane dissolved in the sea surface waters and molecular fractions of dissolved organic matters, and the methane production process originated from methylamine are analyzed. Nitrous oxide and methane have been determined for their concentration and isotope ratios and their behavior are analyzed. Source materials of nitrous oxide including organic nitrogen and inorganic nitrogen containing molecules especially nitrate have been determined for its nitrogen and oxygen isotope ratios so that source and sink process of nitrous oxide has been assessed.Tunable diode laser absorption spectrometer has been calibrated with gas chromatograph systems. Continuous measurement system has been constructed for concentration and flux determinations, and field observation has been started.