Studies On Distribution Of Nitrogen And Phosphorus And Their Adsorption/Desorption Characteriscis In Taihu Lake

Taihu Lake, as one of the five well-known freshwater lakes in China, is currently suffering from eutrophication hazards. The results show that, under the effective control of external source pollution, Taihu Lake is threatened with nitrogen and phosphorus accumulated in the sediment under the joint actions of physical, chemical and biological factors. Environmental dredging has been considered as an important measure to control internal source pollution. Based on above, "research-simulation experimen" idea was used, physical and chemical properties of waterbody and sediment were analyzed, as well as adsorption/desorption characteristics of N and P were studied. The investigation and study on pollution of waterbody and sediment and assessment on ecological risk of N and P will provide technical support for environmental dredging. Major conclusions were described as follows:Water quality was V～inferior V grade, which TN concentration ranged from 0.21 mg/L to 16.06mg/L and TP concentration ranged fom 0.015 mg/L to 2.066mg/L. N and P were mainly distributed in north and west of lake.Taihu Lake was at meso-eutrophic level, which mainly distributed in north and the coast of west. Meanwhile it had the level of medium-nutrient, light-eutrophic, meso-eutrophic and hyper-eutrophic.Sediment subjected to TN, TP and OM pollution and the level was moderate. The average content of TN, TP and OM was 0.118%,0.051%, and 4.84%, mainly distributed in north and east of the lake. The ecological environment in north was fragile and the north would become the focus of dredging area.The process of ammonium/phosphate adsorption and desorption onto sediments reached equilibrium in 2h/12h. Ammonium adsorption was accord with parabolic diffusion model and Elovich model. Phosphate adsorption was accord with Cubic model. Ammonium/phosphate desorption was accord with kinetic model.The ammonium desorption isotherm on sediments from lake was fitted by Henry model in initial ammonium concentration;The phosphate desorption isotherm on sediments from lake was fitted by Linear model in initial phosphorus concentration.The adsorption-desorption equilibrium concentration of N/P was 1.33～1.98mg/L,0.021～0.392mg/L. While the concentration of N/P from waterbody was lower than equilibrium concentration. It could be inferred the risk of nutrient release would happen onto sediment-water interface during the exchange of nutrient.