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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.

将理论上提出的一种直接测量甲烷气体通量密度的微气象新方法--涡积法应用于稻田甲烷生物圈/大气通量密度的测量，研制了一种满足该方法理论要求的新型自动气体采样器。垂直风速w由声波风速计以5 Hz测量并记录在数据记录器上。该速度用于通过当w为正时打开通向储液器的一个阀并且当w为负时打开通向另一储液器的另一阀来确定恒定流速下的条件采样。每隔2小时收集气体样品30分钟，并通过气相色谱法测量平均浓度。利用这些数据，可以估算甲烷通量密度f：f = bsigma_w（C_-C_）为了检验涡动积累法测量的有效性，比较了涡动相关法、波文比法和涡动积累法估算的感热通量密度。<up><down>结果表明，两种方法之间的密切的一致性，表明涡积法的可靠性。应用涡积法与自动气体采样器，测量甲烷通量密度在泰国南部的稻田。通量密度的日变化在20~60 mg/m^2/hr之间，且在下午和午夜后分别出现最大值和最小值。