DEVELOPMENT OF OPEN PATH METHANE SENSOR

开放式甲烷传感器的开发

基本信息

批准号：
06558076
负责人：
OHTAKI Eiji
金额：
$ 4.99万
依托单位：
OKAYAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06558076/
关键词：
EDDY CORRELATION METHOD AERODYNAMIC METHOD METHANE METHANE FLUX メタンガスフラックス熱収支法

项目摘要

Methane is an important trace gas in the atmosphere because its high potential to absorb the outgoing longwave radiation. The absorbing potential is about 20 times that of carbon dioxide. It is well known that the methane concentration in the atmosphere is increasing. The major source of this increasing methane concentration has been assumed to be human activities associated with rice cultivation and animal husbandry. The eddy correlation technique is the most promising method to measure methane flux in the atmosphere. However, this technique requires a fast response and high resolution instrument for methane measurement.A prototype fast response CH4 instrument with open sensing path is developed in the present study. Results of the laboratory and fild test are summarized as follows : (1) The sensitivity of the instrument is about 15.6 ppm per volt. The measuring frequency is 30 Hz. (2) The noise-limited sensitivity is about 0.6 ppm peak-to-peak in CH4 concentration. (3) The sensitivity is practically invariant with a possible change in the adjustment of the optical system. (4) Preliminary test shows that the instrument is feasible for measurements of CH4 flux by the eddy correlation technique under field conditions. However, the present instrument suffers from several limitations. Most serious problem is the inadequate oscillation of He-Ne laser. In order to reduce the noise level of the instrument, further effort is required to control the oscillation of He-Ne laser.

甲烷是大气中重要的痕量气体，因为它吸收了外向的长波辐射的高潜力。吸收潜力约为二氧化碳的20倍。众所周知，大气中的甲烷浓度正在增加。人们认为这种增加的甲烷浓度的主要来源是与水稻种植和畜牧业相关的人类活动。涡流技术是测量大气中甲烷通量的最有前途的方法。但是，该技术需要快速响应和甲烷测量的高分辨率仪器。在本研究中开发了带有开放感应路径的原型快速响应CH4仪器。实验室和FILD测试的结果总结如下：（1）仪器的灵敏度约为每伏15.6 ppm。测量频率为30 Hz。（2）CH4浓度的噪声限制灵敏度约为0.6 ppm。（3）敏感性实际上是不变的，并且可能会改变光学系统的调整。（4）初步测试表明，该仪器在田间条件下通过涡流相关技术可用于测量CH4通量。但是，目前的仪器有几个局限性。最严重的问题是He-Ne激光的振荡不足。为了降低仪器的噪声水平，需要进一步的努力来控制HE-NE激光的振荡。