Carbon isotope of atmospheric methane and its application to the clobal methane cycle

大气甲烷碳同位素及其在全球甲烷循环中的应用

基本信息

批准号：
07454108
负责人：
NAKAZAWA Takakiyo
金额：
$ 4.35万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07454108/
关键词：
Methane Carbon isotope Greenhouse gas Climate change

项目摘要

For a better understanding of the global cycle of methane on the earth's surface, the data of carbon isotopic ratio in atmospheric methane are indispensable. In this study, we made a special instrument for precise analyzes of the carbon isotopic ratio in atmospheric methane with a small amount of air sample. Methane contained in the air samples was converted to carbon dioxide for determining the carbon isotopic rati in methane, by contacting it with 0.5% platinum catalyst supported on alumina pellets at 750ﾟC.It was found that the conversion efficiency of methane to carbon dioxide is 99.9% and an overall precision of our analyzes is 0.07%.Using this instrument and a mass spectrometer, we analyzed the isotopic ratio in methane of air samples collected in the troposhere over Russia. This is the first attempt of measuring the carbon isotopic ratio atmospheric methane in the northern Eurasian Continent. The results showed that methane from natural wetlands and fossil fuel can be estimated separately using its carbon isotopic ratio data. We also analyzed the tropospheric and stratospheric air samples over Japan. It was found from this measurement that the carbon isotopic ratio was fairly constant in the troposphere and increased with height in the stratosphere. Simulations with an one-dimensional photochemical-diffusion model suggested that the reaction of methane with chlorine atoms is especially important for the measured vertical profile of the carbon isotopic ratio. We also developed a two-dimensional transport model with the methane concentration and its carbon isotopic rati, and then estimate global mathane sources and sinks from the observed values of both components.

为了更好地了解地球表面上甲烷的全球循环，大气甲烷中碳同位素比的数据是必不可少的。在这项研究中，我们制作了一种特殊的工具，用于精确分析大气甲烷中碳同位素比，并用少量的空气样品分析。通过将甲烷中的甲烷转化为二氧化碳，以确定甲烷中的碳同位素rati，通过与0.5％铂催化剂在750°C上支撑的0.5％铂催化剂接触。俄罗斯对流层收集的空气样品的甲烷的同位素比。这是测量北欧亚大陆碳同位素比大气甲烷的首次尝试。结果表明，可以使用其自然湿地和化石燃料的甲烷使用其碳同位素比数据分别估算。我们还分析了日本的对流层和平流层空气样品。从该测量值中可以发现，在对流层中碳同位素比相当恒定，并且随着平流层的身高增加。具有一维光化学扩散模型的模拟表明，甲烷与氯原子的反应对于碳同位素比的测得的垂直分布尤为重要。我们还开发了一种具有甲烷浓度及其碳同位素rati的二维传输模型，然后从两个组分的观察值中估计了全局数学源和下沉。