Development of combined measurement method for methane, nitrous oxide and carbon dioxide without gas cylinder by gas chromatography

Greenhouse gas emission from agricultural ecosystems are one of major environmental issue, recently. Our research aim is improving greenhouse gas flux measurement method precisely, inexpensively and automatically in agricultural ecosystems. Measurement method for CO₂, CH₄ and N₂O simultaneous analysis (3GHG-GC) was firstly launched in 2005 followed by automatic gas sampling system (AGSS) in 2006, automatic injector for GC (RoVi) in 2013 and nitrogen generation system from compressed air for precise GC analysis in 2011, respectively. 3GHG-GC was recently further improved that the carrier gas of this method was changed from helium to nitrogen or argon to meet global requirement to save helium consumption. In "3GHG-GC", 3 stages of packed separation column using Porapak Q (Waters Co. Ltd. USA) and Unibeads C (GL Science Co. Ltd. Japan). Shimadzu GC-2014 gas chromatograph equipped with thermal conductivity detector (TCD), flame ionization detector (FID) and electron capture detector (ECD). The carrier gas was purified nitrogen generated by compressed air. The impurity of methane in the carrier nitrogen was eliminated by catalytic chemical treatment to measure precise atmospheric level of CH₄. Finally the system "3GHG-GC" achieved three gas combined precise measurement with standard error of  within 1% without gas cylinder for carrier gases.