长江口及其邻近水域硅酸盐的公布变化特征

Distribution and variation of silicate in the Changjiang estuary and its adjacent waters

Based on the data obtained from quarterly investigations in the Changjiang estuary and its adjacent sea areas in 2004,the distributions and variations of SiO₃-Si are discussed. The reslts show that the concentrations of SiO₃-Si were higher near the changjiang estuary and lower outside ghe sea.Generally,the concentrations of SiO₃-Si were higher in the surface than in the buttomin shore;the opposite distributions off shore.The SiO₃-Si concentrations both inside and outside the mouth in summer and autumn were higher than those in spring and winter.Distributions of SiO₃-Si varied with increase and decrease of runlff and with enlarge and reduce of the extent of Changjiang dilution water.The concentrations of SiO₃-Siin May were relatively less because of phytoplankton blooming. The seasonal variations of SiO₃-Si/DIN and SiO₃-Si/PO₄-P ratios were mainly controlled by the variations of SiO₃-Siconcentrations. Compared with the data of 1985-1986, the concentrations of SiO₃-Sihave inereased2.3 times,both SiO₃-Si DIN and SiO₃-Si/PO ₄-P ratios have ascended 1.6 and2.5 times respectively, which depended on the increasing of the SiO₃-Si concentrations,May is the fitting season of phytoplankton blooming compared with other seasons,in which it is the relaively least that SiO₃-Si/DIN and SiO₃-Si/PO ₄-P ratios departure from Redfield ratios. The removals of SiO₃-Siin the estuary showed that aside from biological removal, there was a main effect coming from seawater dilution.