Measuring CH4 flux in a rice paddy field in Thailand using relaxed eddy accumulation (REA) method

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  • タイ王国の水田におけるCH4フラックスの緩和渦集積(REA)法による測定
  • タイ オウコク ノ スイデン ニ オケル CH ₄ フラックス ノ カンワウズ シュウセキ(REA)ホウ ニ ヨル ソクテイ

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Abstract

Rice paddy fields are a major anthropogenic source for methane (CH4),one of the dominant green-house gases (GHGs). Recently, micrometeorological tech-niques for measuring GHG flux in a fileld scale have been developed. We evaluated a relaxed eddy accumulation (REA) method, a micrometeorological technique, to mea-sure methane (CH4) flux in a rice paddy field during a flow-ering stage in Thailand. CH4 flux at the paddy water sur-face was also measured using the closed chambers installed where no rice plant was grown. The CH4 fluxes with the REA and closed chamber methods ranged between 1.9 mg m-2 h-1 and 43.6 mg m-2 h-1,agreed well with those pre-viously reported in Southeast Asia. The exchange rates of CH4 between the atmosphere and the rice canopy tended to get higher during the daytime, and seemed to be reg-ulated by the diurnal variations of horizontal wind speed and soil temperature. In addition, temporal changes in CH4 fluxes at the water surface might be affected by soil tem-perature. The CH4 fluxes measured with the REA method were higher than those with the closed chamber method. It appears that the REA method measured CH4 fluxes over rice plant canopy and the water surface whereas the closed chamber method did only over the water surface.

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