Development of a long-term methane flux measurement system with REA method

2003 Fiscal Year Final Research Report Summary

• Project/Area Number: 14560218
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 生物環境
• Research Institution: Osaka Prefecture University
• Principal Investigator: HAMATANI Ken Osaka Prefecture University, Graduate School of Agriculture and Biological Sciences, Assistant Professor, 農学生命科学研究科, 講師 (30264815)
• Co-Investigator(Kenkyū-buntansha): HIRANO Takashi Hokkaido University, graduate school of agriculture, Associate Professor, 大学院・農学研究科, 助教授 (20208838) ; MONJI Nobutaka Osaka prefecture university, Graduate school of agriculture and biological sciences, Professor, 農学生命科学研究科, 教授 (20111982)
• Project Period (FY): 2002 – 2003
• Keywords: Global warming / Green house gases / Forest / Methane gas / REA method / Long-term measurement

Research Abstract

We developed a long-term methane flux measurement system with REA method and conducted a continuous observation in forests. The system operates automatically to make flux measurements with micro-computer. We developed the hardware of sampling system and processing parts and software for the long-term continuous estimation. We adopted a methane analyzer with FID detector. Although the accuracy of the analyzer is 50ppb, REA system requires relative concentration differences of two sampled air which this analyzer can detect down to several ppb.
Before we carried out the methane flux measurements, we tested the REA technique for CO_2 flux by comparing with the open-path eddy correlation method and obtained fairy good agreements. For the long term measurement we need maintenance and the calibration of analyzer every one or two weeks. We found this system to work well in the preliminary experiments.
Seasonal trends of methane flux over the forest were observed. In September to October, the flux had negative values that means methane transport from atmosphere to the ground during the daytime. But at night the flux value was almost zero. The methane flux had the correlation with the soil temperature measured at the 1cm depth for over 12C and almost zero below 12C. In November, the flux was almost zero throughout day and night even when temperature exceeded 12G. This difference may have been caused by the difference in the soil moisture content which controls the activities of the bacteria.