Effects Of Dissolved Oxygen Concentration On Phosphorus And Nitrogen In The Sediments From Shallow Lakes

Lake eutrophication is one of the most important environmental problems in our country, furthermore, the studies on phosphorus and nitrogen actions in the interface of sediment-water is the key elements which helps find the mechanism of eutrophication. This paper focus on the effects of dissolved oxygen (DO) on the distribution of phosphorus fractions and the release of phosphorus, ammonium and nitrate of the sediments from the Meiliang Lake and Gong Lake in laboratory simulation, which are shallow lakes, and locate in different polluted areas of Tai Lake. The results are shown as the following.In different DO levels, the reason of the declining of the TP in the sediments is caused by the variation of phosphorus fraction concentrations. In anaerobic condition, the decreasing concentrations of BD-P, NaOH-P and HC1-P is the main reason, in the anoxic condition, the decreasing of TP concentrations mainly originated the decreasing of the concentrations of OP, NaOH-P and HCl-P. Same conclusion can be drawn from the aerobic and DO saturation condition, the decreasing of concentration of both OP and HCl-P is the main reason, and the effect of the HCl-P concentration decreasing in the sediment of Gong lake was more significant than Meiliang Lake.Phosphorus concentrations of the overlying water were all increasing during the incubation for different treatments. The order of the phosphorus concentration in the overlying was: anaerobic condition> anoxic condition> aerobic condition=saturation condition. The rate of phosphorus release was higher in the anaerobic condition than that in DO abundant condition, and that of the sediment with high content of TP is higher than the sediment with low content of TP. DIP that originated from APA was an important phosphorus resource, especially when the DIP of overlying water was lack.There is good relationship between ammonium and DO concentrations of overlying water. When the content of DO is under 1mg/l, the content of ammonium increase. In the other DO condition, the content of ammonium decrease, but the content of nitrate increase in this investigation.