| Project/Area Number |
11680524
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | Yamagata University |
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Principal Investigator |
KASUBUCHI Tatsuaki Yamagata Univ., Faculty of Agriculture, Prof., 農学部, 教授 (00250960)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2000: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1999: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Keywords | Ponded water of a paddy field / Convection / Dissolved oxygen / Caron dioxide / pH / Eh / 対流速度 / 溶存炭酸ガス / 対流速度計 / 光合成速度 / 呼吸速度 / ガス交換速度 |
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| Research Abstract |
It has been considered that the ponded water of a paddy field is in a stationary state and mass is transferred by diffusion. But we found that the water is moving by convection all through the day. We tried to measure the convective velocity in this report. We developed the new measuring method and measured the convective velocity in the paddy field. The method was based on the principle of the twin heat probe and was taken into consideration to average the non-uniform distribution of convective water flow. We measured the velocity by this method. The convective velocity changed daily and reached to the maximum (about 0.1cm/s) around noon. This velocity was about 10,000 times larger than the velocity by diffusion.
Dissolved oxygen and carbon dioxide are measured automatically, which are vital in the ponded water of a paddy field. The dissolved oxygen is generated by the photosynthetic bacteria in the water in daytime. As the result, the concentration of the dissolved oxygen was super saturated in the daytime and unsatutated in the night-time, while the carbon dioxide was changed oppositely. But the relation between the two was not opposite exactly and made hysteresis loop. We made clear that this phenomenon was caused by the difference between reaeration and deaeration coefficients of the two gases. From these results, we could separate the rate of oxygen production by photosynthesis, that of respiration and that of exchange at the water surface. We also found that the pH of the ponded water changed between 7 and 10 daily and this was caused by the change in the concentration of carbon dioxide. Furthermore, we found that the Eh of the ponded water and the surface soil changed daily in accordance with these changes.
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