Measurements of methane flux densities from paddy fields by eddy accumulation method

涡积法测定稻田甲烷通量密度

基本信息

批准号：
03806039
负责人：
ISHIDA Tomoyasu
金额：
$ 1.22万
依托单位：
Utsunomiya University (1992)Yamagata University (1991)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-03806039/
关键词：
eddy accumulation method eddy correlation method Methane flux paddy field フラックス微気象学的方法

项目摘要

Eddy accumulation method, which had been proposed theoretically as a new micrometeorological method to directly measure the gas flux density from the sources, were applied to measure the biosphere/atmosphere flux density of methane from paddy fields.A new automatic gas sampler, which satisfies the theoretical requirements of this method, was developed. The vertical wind velocity w is measured with 5 Hz by the sonic anemometer and recorded on the data-logger. The velocity is used to determine the conditional sampling at a constant flow rate by opening one valve to a reservoir when w is positive and another valve to another reservoir when w is negative. The gas samples are collected for30 minutes in every 2 hours and average concentrations are measured by gas chromatography. Using these data, methane flux density f can be estimated as follows: f=bsigma_w(C_<up>-C_<down>)In order to check the validity of the measurement of the eddy accumulation method, the sensible he at flux densities estimated by the eddy correlation method, the Bowen ratio method, and the eddy accumulation method were compared. The result shows close agreement between two methods and suggests the reliability of the eddy accumulation method.Applying the eddy accumulation method with the automatic gas sampler, methane flux densities from a paddy field were measured in the south of Thailand. The daily courses of the flux densities changed between20 to 60 mg/m^2/hr. Also, they showed maxima and minima in the afternoon and after-midnight, respectively.

在理论上提出的涡流积累方法是一种新的微气流方法，用于直接测量来自源的气体通量密度，用于测量帕迪田的甲烷的生物圈/大气通量密度。垂直风速W用声音仪表测量5 Hz，并记录在数据库中。速度用于确定恒定流速的条件采样，当W是正时，当W为正时，将一个阀向储层打开，而当W为负时另一个阀门到另一个储层。每2小时收集30分钟的气体样品，平均浓度通过气相色谱法测量。使用这些数据，可以估计甲烷通量密度F如下：F = BSIGMA_W（C_ <up> -C_ <dound>），以检查涡流累积方法测量的有效性，这是由涡流相关方法，Bowen比率方法和EDDY累积方法估计的磁通密度的敏感性。结果表明两种方法之间的一致性紧密，并提出了涡流累积方法的可靠性。使用自动气体采样器将涡流累积方法涂抹，在泰国南部测量了来自稻田的甲烷通量密度。通量密度的每日课程在20 mg/m^2/hr之间变化。另外，他们分别在下午和午后分别显示出Maxima和Minima。