DIRECT MEASUREMENTS OF CARBON DIOXIDE EXCHANGERATES ACROSS AIR-SEA INTERFACE WITH EDDY CORRELATION TECHNIQUE

研究了二氧化碳的海气交换速率。结果表明：（1）涡动相关法测得的CO2通量平均值约为0.10 mg·<-2>m <-1>~（-3）·s ~（-1），标准差为0.09 mg·<-2>m ~（-3）·s ~（-1）<-1>，表明CO2通量是向上的。这些值是在1986年10月和1987年在日本海获得的范围内，而目前的通量约为十分之一的向下通量的二氧化碳测量积极增长的稻田。值得注意的是，涡动相关技术测量的二氧化碳通量与空气动力学和散装技术测量的结果一致。(2)pCO_2测量仪用于测量与样品海水相平衡的载气中二氧化碳的浓度。测定pCO_2只需150 ml海水。该仪器每隔20分钟可测一次pCO_2，测量精度约为2 ppm。(3)pCO_2的温度系数约为4.5%pCO_2/℃，盐度系数约为44 ppm/盐度单位。(4)测定的pCO_2值具有明显的日变化，夜间高，白天低。这种日变化主要是由于海水中光浮游生物的光合活性造成的。(5)CO_2通量的变化导致海水中pCO_2的变化。而CO_2通量对pCO_2的相对变化较小，每天小于1 ppm。(6)pCO_2数据表现出夏季高、冬季低的季节变化规律。季节周期的振幅约为150 ppm。与大气中的pCO_2相比，6 ~ 11月海水中的pCO_2较大，主要是将CO_2从海面输送到大气中; 12 ~ 5月至1月海水中的pCO_2较小，主要是将CO_2从大气中输送到海水中。

The air-sea exchage rates of carbon dioxide is studied. The primary results obtained are summarized as follows : (1) The mean value of total carbon dioxide fluxes measured by the eddy correlation technique was about 0.10 mg m^<-2> s^<-1> with the standard deviation of 0.09 mg m^<-2> s^<-1>, showing the upward flux of carbon dioxide. These values are within the range obtained over the Sea of Japan during October 1986 and 1987, while present fluxes are about one tenth of the downward flux of carbon dioxide measured over actively growing paddy fields. It is noted that the carbon dioxide flux measured by the eddy correlation technique agrees with those measured by both the aerodynamic and bulk technique. (2) The pCO_2 instrument is designed to measure the carbon dioxide concentration of carrier gas which equilibrates with the sample seawater. Smple seawater of 150 ml is enough to determine pCO_2. The instrument can measure pCO_2 every 20 min and its measuring precision is about 2 ppm. (3) The temperature and salinity coefficients of pCO_2 are determined to be about 4.5%pCO_2/ﾟC and about 44 ppm per salinity unit, respectively. (4) The pCO_2 measured shows well defined diurnal variation with high values in the nighttime and low values in the daylight hours. This diurnal variation is due mainly to the photosynthetic activity of photoplanktons in seawater. (5) The CO_2 flux results in the change of pCO_2 in seawater. However, the relative change of pCO_2 due to the CO_2 flux is small less than 1 ppm per day. (6) The pCO_2 data show seasonal cycle with high values in summer season and low values in winter season. The amplitude of seasonal cycle is about 150 ppm. Comparing with the PCO_2 in the atmosphere, the pCO_2 in seawater is larger during periods from June to November, transporting carbon dioxide from the sea surface to the atmosphere, and smaller during periods from December to May through January, transporting carbon dioxide from the atmosphere to the seawater.