Estimation of the origin of atmospheric methane by the use of atmospheric diffusion analysis and measurements of atmospheric radioactivity and isotope ratio.

通过大气扩散分析和大气放射性和同位素比的测量来估计大气甲烷的来源。

• 批准号: 08458144
• 负责人: IIDA Takao
• 金额: $ 3.65万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08458144/
• 关键词: methane flux; radon; diffusion equation; isotope ratio; non-fossil fuel; paddy field; diurnal variation; atmospheric diffusion; メタン発生率; 乱流拡散係数; 炭素同位体比

A Method was examined for evaluating methane flux by comparing measured value of methane concentration in air with calculated one from numerical analysis of a diffusion equation. The numerical values for the variation of radon concentration obtained by using one-dimensional non-steady state diffusion equation explain well the temporal variation of radon concentration : Thus the reliability of the numerical solution of the diffusion equation was revealed, and we can determine the methane flux by using the numerical analysis method.Taking notice of the similarity of the diurnal variation pattern of methane and radon concentrations in air, a method was developed for evaluating methane flux based on the knowledge of the behavior of radon in air. The averaged methane flux at the suburbs of Nagoya city area was obtained. At the south-west part of Nagoya city, regional methane flux increased in July and August and it amounted to 0.068 CH_4・m^<-2>・d^<-1>. According to the analysis of carbon isotope ratio of methane sampled at a site of Yatomi, it revealed that almost all of the methane are supplied from non-fossil origin ; It is considered to originate from paddy field.A method for evaluating vast aerial non-uniform flux of methane was proposed by using the similarity of the diurnal variations of radon and methane. The amount of annually flux was 15.12 GgCH_4 in Aichi prefecture and was 1.52 GgCH_4 in Nagoya city.

通过比较空气中的甲烷浓度的测量值与从扩散方程的数值分析计算出的方法，检查了一种方法来评估甲烷通量。通过使用一维非稳态的状态扩散方程获得的ra浓度变化变化的数值值很好地解释了ra浓度的暂时变化：扩散方程的数值溶液的可靠性已显示出来，我们可以通过使用数值分析方法来确定甲烷通量的甲烷通量。根据对空气中ra的行为的了解来评估甲烷通量。获得了名古屋市地区郊区的平均甲烷通量。在名古屋市的西南部，7月和8月的区域甲烷通量增加，占0.068 CH_4・M^<-2> d^d^<-1>。根据在Yatomi部位采样的甲烷的碳同位素比的分析，它表明几乎所有甲烷都是从非化石起源提供的。它被认为是源自稻田。通过使用ra和甲烷的昼夜变化的相似性，提出了一种评估甲烷巨大的空中非均匀通量的方法。 AICHI预防的年度通量为15.12 GGCH_4，在Nagoya City为1.52 GGCH_4。