| In combination with the cogredient data of hydrology, chemistry and biology, the data of surface water CO2 partial pressure (pCO2) at grid stations in the Bohai Sea, August,2006 and in the Laizhou Bay, July,2005, is served to discuss the distribution of the pCO2 and the main factor controlling the formation of source and sink. Based on the study, we give the air-sea flux of CO2 in the Bohai Sea in summer. For the sake of better understanding of the river discharge impact on carbon system in the Bohai sea, researches are taken on the Lijin station during June in 2006 when the Huanghe river has the largest input to the Bohai sea. Based on the data, the main factors of the pCO2 distribution and the carbon flux carried by the Huanghe river to the Bohai Sea are given, at the same time, the proportion of the carbon flux of the water and sediment regulation period in the whole year is estimated. The main conclusions are drawn as follows:1. During the water and sediment regulation period, the average of pCO2 in Lijin station is 1570μatm, which is much higher than the other period of the year. A good positive correlation has been found between pCO2 and DIC, suggesting that the pCO2 is controlled by the carbonate system and many sediments buffering the carbonate system led to high pCO2.In the later stage of the water and sediment regulation period, the impact caused by the biological aerobic respiration gradually appears, but it's still not the main control factor. At the same time, photosynthesis has been enhanced, leading to the decrease in pCO2.2. During the water and sediment regulation period in 2006,caron flux in DIC,PIC,DOC,POC carried by the Huanghe River into the sea respectively are 1.38×105tC,1.87×105tC,1.05×104tC,4.93×104tC. During the other period, caron flux in DIC,DOC,PIC,POC carried by the Huanghe River into the sea respectively are 4.93×105tC,8.28×105tC,3.42×104tC,5.25×104tC. The proportion of the water and sediment regulation period in the whole year are 21.9%,69.3%,23.5%,48.4% respectively. In order to estimate more reasonably, we take DIC,DOC,POC count the total carbon flux. The result is that the water and sediment regulation period account for 25.4% of total carbon flux into the sea in the whole year, implying the special period of the Huanghe River has a substantial influence on carbon flux from the river into the sea.3. The magnitude of pCO2 ranged between 313-1118μatm, and the mean was 537μatm, which showed the region acted as a source of CO2 on the whole except the area near the bank of the middle sea(119°E-120.5°E,38.5°N-40°N)and the east of the Liaodong Bay (120.7°E-121.2°E,39.9°N-40.1°N)which acted as a sink of CO2 and the sum of the sink area accounted for one fifth of the whole area. 4 The distribution of the pCO2 in the Bohai sea in summer is mainly controlled by two factors. With the impact of the river which has a high carbonate value, the source area shows a high concentration. The formation of sink is mainly caused by the strong biological activity in the area where the clean water and high diaphaneity existed. The temperature affects the source area and the sink area respectively, but it's not the controlling factor.5. In the source area, with the impact of the river discharge, especially in the area affected by the Huanghe River, DIC and PIC show a substantially high value, leading to a high pCO2 by the carbonate system. Because of the increase of [HCO3-], the Huanghe estuary and the area around forms a low-pH-area. In the sink area, chlorophyll is much higher than the other area, which leads to the enhanced photosynthesis process and finally to the decrease of pCO2 and DIC.6. The average air-sea flux in the Bohai Sea in summer is 123.5×104tC. Even though there is a sink area in the Bohai Sea, it's much weaker compared to the source. On the whole, the Bohai Sea acts as a source. In the area with salinity below 31, it appears to be a strong source impacted by the discharge of the Huanghe River, implying the strong effect on the strength of source caused by the Huanghe input.
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