Evaluation of sources of atmospheric methane using isotopic measurement and diffusion model analysis
| Project/Area Number |
05452398
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | Nagoya University |
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Principal Investigator |
IKEBE Yukimasa Nagoya University, School of Engineering, Prof., 工学部, 教授 (50023073)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIDA Naohiro Nagoya University, Institute for Hydrospheric-Atmospheric Sciences, Associate Pr, 大気水圏科学研究所, 助教授 (60174942)
NAKAMURA Toshio Nagoya University, Dating and Materials Research Center, Associate Prof., 年代測定資料研究センター, 助教授 (10135387)
NAGAMINE Koichiro Nagoya University, School of Engineering, Research Associate, 工学部, 助手 (10242843)
IIDA Takao Nagoya University, School of Engineering, Associate Prof., 工学部, 助教授 (50089843)
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| Project Period (FY) |
1993 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥6,500,000 (Direct Cost: ¥6,500,000)
Fiscal Year 1995: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1994: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1993: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Keywords | Global warming materials / Atmospheric methane / Concentration equipment of trace of methane / Carbon isotopic composition / Accelerator mass spectrometry / Continuous measurement of methane concentration / Atmospheric radon / Meteorological analysis / 発生源 / 埋立地 / 同位体比 / 炭素14 / 大気拡散 |
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| Research Abstract |
The fluxes of atmospheric methane (CH_4) from Nagoya area were estimated. The diurnal fluctuations of atmospheric methane observed at 13 sites in Nagoya city and atmospheric radon (^<222>Rn) observed at Nagoya University were in phase. Both methane and radon-222 are released from the ground surface into the atmosphere, and are less chemically reactive. From their similarities of the observations and features, their behaviors in the atmosphere are expected to be similar. By analogy with radon-222, the diurnal fluctuation of atmospheric methane are affected by local meteorological conditions and local methane emission from the area within several tens of kilometers. From the correlations between the concentrations of atmospheric methane and radon-222, the areally averaged fluxes of methane were estimated. Nagoya area was net source of atmospheric methane. In urban area the areal fluxes were less than 0.02 gCH_4m^<-2>d^<-1> and almost constant through the year, whereas in suburb the areal
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flux increased to 0.04-0.06 gCH_4m^<-2>d^<-1> from July to August.
The preparation system for carbon isotopic measurement, especially ^<14>C measurement by accelerator mass spectrometry (AMS), for atmospheric methane was assembled. The performance of the system is sufficient for AMS.
The types of local methane sources and their contributions were estimated from the change of carbon isotopic compositions (delta^<13>C,^<14>C/^<12>C) in the consequence of the fluctuations of the concentrations of atmospheric methane. Almost all of methane released from urban area in winter was fossil methane which is depleted in ^<14>C and derived from anthropogenic sources such as leakage of natural gas. While, fossil methane released from suburban area contributes less than 10% of the diurnal methane in summer when methane emission increases. The estimated delta^<13>C value of non-fossil methane was -65@91 and suggested that non-fossil methane was bacterially produced in anaerobic environment. Thus, the increase of areal flux of methane in suburb in summer would be attributed to rice paddy fields. Less
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Report
(4 results)
Research Products
(6 results)
