Evaluation of sources of atmospheric methane using isotopic measurement and diffusion model analysis

利用同位素测量和扩散模型分析评估大气甲烷来源

基本信息

批准号：
05452398
负责人：
IKEBE Yukimasa
金额：
$ 4.16万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05452398/
关键词：
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

项目摘要

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 … More 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

估计了纳戈亚地区的大气甲烷（CH_4）的通量。在名古屋市的13个地点和大气ra（^<222> RN）观察到的大气甲烷的差异波动是相位的。甲基和rad-222均从地面释放到大气中，化学反应性较低。从它们的观察和特征相似之处，他们在大气中的行为有望相似。通过与ra-222的类似，大气甲烷的根本波动受到局部气象条件的影响，并在几十公里内的局部气象条件和局部甲烷发射的影响。从大气甲烷和rad-222的浓度之间的相关性中，估计了通常平均的大气甲烷通量。名古屋地区是大气甲烷的净来源。在城市地区，面积通量小于0.02 GCH_4M^<-2> d^<-1>，几乎一直持续到一年，而在郊区……更多的通量增加到0.04-0.04-0.06 gch_4m^<-2> d> d> d^<-2> d^<-2> d^<-1>从七月到八月。（AMS），用于大气中的甲烷。该系统的性能足以适用于AM。局部甲烷源的类型及其贡献是根据碳同位素组合物的变化（Delta^<13> C，^<14> C/^<12> C）的变化，这是由于大气甲烷浓度的波动而导致的。冬季，几乎所有从市区释放的甲烷都是化石甲烷，它在 ^<14> C中耗尽，并源自人为来源，例如天然气泄漏。而当甲烷排放量增加时，从郊区释放的化石甲烷贡献了不到昼夜甲烷的10％。估计的非化石甲烷的Delta^<13> C值为-65@91，并建议非化石甲烷是在厌氧环境中产生的细菌。这是夏季郊区甲烷的甲烷的增加将归因于稻田田。较少的