Comparison of observed air-water CO2 fluxes by the eddy covariance system and the profile method

• Main Authors: Yi-Chih Wang, 王奕智
• Other Authors: 莊秉潔
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/51529065971356246263

碩士 === 國立中興大學 === 環境工程學系所 === 100 === CO2 flux has been estimated by close path CO2 analyzer for decades. Recently, Open path CO2 analyzer has been used in CO2 flux measurements over ocean. However, there still exited significant difference between each other. The purposes of this study are to compare the CO2 flux measured from (1) two open path eddy covariance systems (ECS) at 40 centimeter and 16 meter above the water surface; (2) the profile method sampling at 10, 15 and 20 centimeter above the water surface; (3) the underway-pCO2 system and (4) the dissolved oxygen method. The study site is located at Black-faced Spoonbill Conservation Association in Cigu Dist. The results showed that the CO2 fluxes of all methods is of diurnal cycle variation in which the CO2 fluxes were usually negative during daytime and positive at night. However, the CO2 fluxes of underway-pCO2 system were positive (source) during study period. The magnitude of CO2 fluxes of profile method are usually greater than those of ECS and dissolved oxygen method with 10 to 100 times. The underway-pCO2 system is less than the ECS and dissolved oxygen method with 10 times. During the day, the algae in water absorbs CO2 for photosynthesis and releases CO2 at night which is constituent with the results of the ECS.. Although the ECS at 16 m has larger footprint than that at 40 cm and other methods and the results are considered to be the regional fluxes, only small difference between micrometeorologist for the similar land cover around the study site. The maximum CO2 fluxes of ECS usually occurred around 3 PM and a obvious delay time existed compared to the time of maximum solar radiation. During the experiment period, the sampling inlet of dissolved oxygen methods was changed to the depth of 5 cm and 60 cm below water level every 40 minutes. It can be seen that at both the depth, the dissolved oxygen were similar which implied the stratification effects in water are not significant.