近50年来长江入海溶解硅通量变化及其影响

 对大通、玉树、上海等水文气象观测站近50年来的降雨量、流量、溶解硅(Dsi)、溶 解无机氮(DIN)、溶解无机磷(DIP)、输沙量等记录资料进行分析,结果表明,近50年来长江硅 通量呈明显下降趋势,1959~1984年减少了53.33μmol/L,主要由流域内众多水利工程建设、 化肥农药等工农业生产所产生的富营养化所致;溶解硅通量与输沙量呈正相关、与DIN、DIP 呈负相关,但与流量和降雨量的相关性较复杂:当流量、降雨量分别小于27 386m³/s、1210 m m/a时为正相关,当流量、降雨量分别大于27 386m³/s、1210mm/a时为负相关.这种现象将可 能导致长江口和东海的生物营养盐限制因素由N限制、P限制向Si限制发展.

Changes of dissolved silicate flux from the Changjiang River into sea and its influence since late 50 years.

The materials recorded by Datong、Yushu and Shanghai hydrologic meteorological observatories since late 50 years, including rainfall, flow, concentrations of dissolved silicate (Dsi)、DIN(NO3-)、DIP(P2O5) and silt discharge were analyzed. The results show a sharp decrease trend of Dsi flux in the Changjiang River since late 50 years; and 53.33μmol/L of the dissolved silicate concentration decreased from 1959 to 1984, which came mainly from the dam constructions and the eutrophication formed by industry and agriculture of fertilizer, pesticide, etc. The relation of Dsi flux with silt discharge is positive, but negative with DIN and DIP; and complex with flow and rainfall: positive as flow<27 386 m3/s and rainfall <1210 mm/a but negative as they are greater respectively. It will lead to the development of limiting factor of biologic nutrients in the Changjiang River estuary and East China Sea from N limiting and P limiting to Si limiting.