Research On The Biogeochemical Mechanism Of Silicon At The Main Stream And Estuarine Of Yangtze River

Since the impounding of Three Gorges Reservoir, a narrow river channel-kind reservoir was formed at the upstream of Three Gorges Reservoir, which resulted in slower current, better transparence, and longer retention time of water body. Furthermore, all the above changes are believed to cause significant changes of the biogeochemical dynamics of silicon and the related ecological system structure. Aimed at a deep understanding of the changing process of silicon and providing preliminary data for the study of phytoplankton ecology system, three in-situ cruises were carried out at April, May and Oct.2005, separately, at the upstream of dam, the main stream and the estuarine of Yangtze River, focusing on the detailed temporal and spatial distribution of dissolved silicon, and a preliminary study on the suspended particulate biogenic silicon and lithogenic silicon was performed with improved Ragueneau Method based on conditions of our laboratory. Primary conclusions are listed as follows:At the end of the extraction of biogenic silicon by Ragueneau Method, 2.5ml remnant liquid was freeze-dried. AlCl3 was added to the extracted-liquid during the analysis of diagenesis silicon, in order to eliminate the disturbing effects of HF. The standard deviation of the measurement of the biogenic silicon in the Three Gorges Reservoir is 2.8% with the improved method, and under the same method and conditions, inshore standard sediment sample (GBW07314, the total silicon content is 28.98%) is analyzed, with the result as 28.53%±0.67%(n=8),relative standard deviation is 2.34%, which is 1.56% different from standard value. From the fact above, we can safely draw the conclusion that this method is characteristic of high stabilization and high degree of precision.