The Research Of Donghu Lake Sediment On Characters Of Phosphorus Adsorption-release And Control Measures

As one of the largest urban lakes in China, Donghu lake is a typical urban shallow lake. Like many other lakes, it has become hypertrophic due to decades of excessive increase in the input of nutrients, through domestic sewage and agricultural run-off. In order to provide scientific guide for prediction and control of the eutrophic level in Donghu lake, it is necessary to study the biogeochemical processes of key nutrients, such as phosphorus, and their controlling conditions.(1)A pilot experiments study showed that pH, disturbance and temperatures affected the release of P from the sediment and the adsorption of P to sediment. Phosphorus release rate from the sediment was highest at high pH and smallest at neutral pH conditions. The increase in temperatures and disturbance of the water influenced P release from the sediment. The pH and temperatures are the most important factors affecting P release from the sediment.(2)It was complex that the kinetics process of P adsorption-release by Donghu lake sediment. And the process developed to a state of dynamic balance at last. At a high content of phosphorus in water, sediment adsorbed phosphorus from water; at a low content of phosphorus in water, sediment released phosphorus to water. The content of phosphorus between water and sediment kept balance. It caused the content of phosphorus in the overlying water tend to a level.(3)Aluminum chloride, ferric chloride and aeration were tested to control internal phosphorus release. The results showed that when pH value varying from 7 to 10, the effective dosage of aluminum chloride and ferric chloride increased from 30mg/L to 50mg/L and from 10mg/L to 15mg/L respectively, both the effects of aluminum chloride and ferric chloride at pH 4 were not significant. While in the use of aeration which is less significant, the concentration of soluble phosphate in the overlying water decreased and stabilized after 5 days.