Study On The CO₂ Flux At The Estuary Of Yangzte And Huanghe And PCO₂ Estimate Model Of East China Sea

Continental margins, considered potential sinks for missing anthropogenic carbon, have come under increasing attention in recent years. The East China (ECS) sea is a major marginal sea in the Northwest Pacific, Bohai is almost closed in land. As Yangzte and Huanghe flow respectively into them, they will play important role in carbon flux and balance of Chinese marginal sea. There are few research on pCO2 about the estuary of Yangzte and Huanghe so far. So study on the CO2 flux at the estuary of Yangzte and Huanghe is of great importance for the discussion of global carbon cycle and for the consummation of the global carbon database.The data, obtained from the four cruises in July, 2001 and January, 2002 for Yangzte estuary and August, September 2003 for Huanghe estuary. We disccuss the distribution of pCO2 and its influence aspects in every cruise. The article is divided into four parts: (1) the survey area and measurement methods; (2)the distribution of pCO2 and its influencing mechanism in Yangzte marginal sea in summer and winter; (3)the pCO2 distribution and CO2 flux of Huanghe estuary; (4)build an estimating model for pCO2 which based on surface seawater of East China Sea.There is a super-high pCO2 (301 station, 617.0atm)in the turbidity water nearby the Yangzte river-mouth, and it decrease rapidly to 300atm at a short distance. It should for the sake of Yangzte freshwater discharge, mixing of freshwater and seawater, turbidity decrease rapidly which result in improving biological activity.pCO2 increase closely with increasing salinity, but decrease with increasing temperature and Chl-a in summer surface seawater except high turbidity water. In contrast, pCO2 exhibit a conservative behavior with them in winter. In summer, during the diffusing of Yangzte freshwater to NE, turbidity decreasing, Temperature is stratified, abundant nutrients which result in significantly enhanced biological activities, and thus lead to pronouncedly increased consumption of CO2. In winter, biological activity is inhabited, in course of Yangzte freshwater flowing from west to east, pCO2 decrease gradually with temperature and salinity increasing. The authorproposes that freshwater which salinity is below 30 lead to west of ECS being CO2 source in summer and sink in winter. Despite the freshwaters, such as Changjiang River and Hangzhou Bay, which including high pCO2, but it also bring with abundant nutrients which result in significantly enhanced biological activities, and thus lead to pronouncedly increased consumption of CO2. Based on analysis of control parameters which affect the variation of pCO2 in summer and winter, we build an estimating model for pCO2.Using three gas exchange coefficients calculated from the Wanninkhof model (Wanninkhof, 1992;1999), Liss & Merlivat (1986) and the average wind speed, to the estuary of Huanghe, The sea of survey area (1.852 103 km2) is estimated to release about 2.7 l04 tC to atmosphere in summer, respectively, 11.4xl04 tC is released from the research sea (9.693 103 km2 ) in autumn.