| In the study of global carbon cycle, the continental margin, being considered one of the potential sinks of the missing term of carbon, has become the focus of researches in the past few decades. It is of great importance, for the discussion of global carbon cycle and for the consummation of the global carbon database, to study the COi flux over the East China Sea since it is one of the important marginal seas in Northwest Pacific.In this dissertation work, a new shower-bubble type equilibrator is developed, and is double-checked with the laminary flow type equilibrator made by Cooper (1998). Significance test shows no distinct discrepancies between the two. The new equilibrator can measure the pCO2 not only at the sea-atmosphere interface, but also under deep-sea water. Moreover, a photometric pCO2 determination method, based on the combination of membrane separation of hydrophobic microporous PTFE and the flow injection technique, is established. Data of pCO2 are then obtained using the new method from five cruises in February 1997, August 1997, August 1998, August 1999 and July 2001. Based on these data and those measured by Yuanhui Zhang in spring and autumn of 1994, the CCb absorbing capability of the East China Sea in four seasons has been estimated. By combining the observed pCO2 data and the cogrediently monitored hydrological, chemical and biological data, the distribution characteristics, their influencing factors and the reasons for the spatial change of CO2 sources and sinks are discussed.It is brought forward for the first time that in summertime the pCO2 of the surface water near the Changjiang estuary, whose salinity is less than 20, decreases dramatically from upwards of 800uatm to downwards of 300uatm within the range of less than half one latitude, suggesting a transformation of a strong CO2 source to a CO2 sink in a finite space. This phenomenon is confirmed by repeated measurements in three consecutive summers. The suddenly intensified biological activities, led bythe mixing of high mud-content freshwater and salty water and the rapid sedimentation of course, are believed to be responsible for the phenomenon. Ulterior researches are needed for verifying and detailing the mechanism.It is indicated that, because of the strong influence of fluvial carbonates, the pCO2 of surface water in the Changjiang estuarine area and near the Hangzhou Bay were obviously higher than the pCO2 of air (especially in summer, autumn and winter), while the pCO2 in the mid East China Sea was apparently lower than the atmospheric pCO2. It is also shown that the pCO2 in the southern East China Sea, near the Black (Kuroshio) Current, is higher than atmospheric pCO2, especially in spring and summer. These characteristics make it very clear that factors influencing the sea-atmospheric exchange of CO2 in marginal continental shelf seas are very much complicated than those in open oceans.The author proposes that it is mainly the freshwater of Changjiang River that leads to the sink of CO2 in the East China Sea in summer. The freshwaters, such as Changjiang River and Hangzhou Bay, bring with abundant nutrients which result in significantly enhanced biological activities, and thus lead to pronouncedly increased consumption of CO2. That makes the seawater to be the sink of atmospheric CC^. Biological activities are also vigorous at the boundaries of freshwater and shelf water, including the boundaries of water masses and the upwelling areas. The sink of CO2 is thus further enlarged. Therefore, the surface mid East China Sea is a sink of atmospheric CO2 (especially in summer), even though there are abundant freshwater with high content of CO2 input to it. The East China Sea as a whole is consequently doomed to be a sink of atmospheric CO2.Using the gas exchange coefficient calculated from the Wanninkhof model (Wanninkhof, 1992) and the wind speed on spot, the net average annual carbon flux at the sea-atmosphere interface over the East China Sea area is estimated to be about 523×104 tC. The sea absorbs...
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