Study On The Distribution And Influence Mechanism Of PCO₂ In The Yangtze River Mainstream And Estuary

Study on the carbon cycle is the central content in the IGBP, the fossil fuel and other human activities can release more than 6×109tC/yr(Houghton et al.,2001;Noble,2001),from our observation, we conform that about half of them still in the atmosphere. Since the Industrial Revolution, the fossil fuel and other human activities have changed the global carbon cycle. CO2 and other"green house"gases have being the important factor to influence the global climate. Human activities not only strengthen the exchange quantity of CO2 between atmosphere,sea and earth ecosystem, but also the river transport carbon directly and the run off of land carbon. So if we want to realize the carbon cycle progress in the earth ecosystem thoroughly and systemic, we must know the quantity and rules between land-sea systems from river.Yangtze river is the longest river in our country and the third long,fifths discharge,fourth sediment quantity in the world (Eisma,1998);The average concentration of HCO3- is 1.66mo1/m3, which is offered 45.7% by carbonate and 54.3% is offered by atmosphere CO2 what consume in the rock weathering. Therefore, Yangtze river drainage basin consumes atmosphere CO2 is 828.00×109mol by rock weathering, which about 3.45% of the rock weathering in the world drainage basin and it consumes the mostly atmosphere CO2 in the Yangtze river drainage basin.We investigate the Yangtze estuary in the Feb. 2006 and from Fuling to Nantong in the April to May, 2006. Meanwhile, we investigate the Yangtze River in Anqing twice a month from May, 2006 to May, 2007. The main content of the paper as flowing:pCO2 varies from 867 to 1651μatm; the average is 1106μatm in the mainstream of Yangtze river. This is lower than other important river in the world and it is the source of CO2. The upper reaches of Fengjie in the Three Gorge, the pCO2 is subjected to the biological aerobic respiration, the lower reaches of Fengjie in the Yangtze river, and the pCO2 is subjected to the carbonate system. After the first impound of Three Gorge, the DIC concentration in the mainstream of Yangtze river is 1.36 to 2.8mM, a little higher than not impound. The main reason of DIC decrease from upper to lower is dilution by Dongting lake and Poyang lake. The average of PIC in the Yangtze river mainstream is only 0.04 mg/l; this is because of the difference source of sediment. In Anqing, the pCO2 in the Yangtze river is subjected to pH; In winter Yangtze estuary, the pCO2 is subjected to pH and temperature.