| Summary: | 碩士 === 國立臺灣師範大學 === 海洋環境科技研究所 === 97 === The distribution of CO2 in the surface water and the sea-air flux exchange in the sea areas around Taiwan are investigated in this study, and to discuss the reason of variation and the relationship with the distribution of water mass. Automated Underway pCO2 System are used to detect the seawater and air fCO2 during the late spring and early summer of 2008, from May 28 to July 13, including the South China Sea(SCS), the West Philippine Sea(WPS), the Western Taiwan Coast(WTC), and the East China Sea(ECS). The range of the atmospheric fCO2 is 367.4~402.2 μatm and the peaks are found near lands (Taiwan, China, and Luzon Island), the difference of concentration up to 35 μatm. The ranges of the surface water fCO2 are as follows: SCS: 352.3~415.6 μatm(Avg.= 389.3±16.5, n=1400), WPS: 346.9~399.0 μatm(Avg.= 377.6±5.8, n=840), TS: 370.5~407.3 μatm(Avg.= 389.2±4.8, n=836), ECS: 162~707 μatm(Avg.=378±69, n=1497); and ECS has the highest variation up to 545 μatm. The lowest and second lowest values of fCO2(217、162 μatm) are found in Changjiang Plume and Minjiang Plume, increasing from west to east with longitude and opposite to the concentration of chl-a. It’s quite obvious that the gradient of seawater fCO2 increase with the decrease of the biomass of plankton. The high values of fCO2(707、676 μatm) are found in Changjiang Upwelling and Coastal Upwelling which have low temperature. These areas also have very low transmittance(13.9 %) and very high nutrients(NO2+NO3) and Chl-a(32.2 μM, 106.7 mg/m3). It’s speculated that the high fCO2 may come from the bottom water of Changjiang Upwelling and Coastal Upwelling. Water masses in SCS and WPS are more stable and have the fCO2 gradient increase from shelf to offshore because the low temperature and rich of chl-a in nearshore seawater make the fCO2 of water decrease. In offshore, the fCO2 of SCS and WPS are high in daytime and low at night(△fCO2 =7.9), mainly reflecting the temperature difference between day and night(0.2~0.3℃) because of low biological effect. The surface water fCO2 of WTC has few variations but the atmospheric fCO2 has regional peaks because it is influenced by terrigenous matter. Data in this study suggests that the sea areas around Taiwan served as a source of atmospheric fCO2 during late spring and early summer, and the sea-to-air CO2 flux in SCS is +1.74±2.06 mol C/m2/yr, in WPS is +0.54±0.59, in WTC is +0.29±0.18, and in the ECS is +0.28±4.94.
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