Studies On Phosphorus Pollutions In Dianchi Lake And On Strategy For Restoration Of Eutrophicated Water

The phosphorus concentrations of water and sediment in Dianchi lake was analyzed and the locations of sampling points were determined using GPS. This study aims to develop effective P pollution control strategies through simulating experiments in laboratory. Our investigation shows that Dianchi has been on over-eutrophication, and the average concentration of total phosphorus in the lake was 0.222mg/L, which was much higher than the international accepted critical levels (TP: 0.02mg/L). Data of dissolved total phosphorus in sediment demonstrates that the phosphorus load in Dianchi lake was relatively high and the average concentration of dissolved total phosphorus was 1.512mg/g, indicating that there were enough phosphorus sources for algal growth.Eutrophication triggered undesirable cyanobacterial blooms and the direct-token was algae and cyanobacteria mats which severely destroyed the vision of lake. During the World's Fair in Kunming, the government applied medicament to Dianchi Lake to kill algal and eliminate algal blooms. However, laboratory studies shows that killing algal by medicament is of no practical use for eutrophication management and recovery in the long term. The dead algal could release nutrients in cells into the water to join the following material cycling, and then the second algal blooms appeared.Sediment dredging has been widely employed in eutrophicated management. For example, at the West Lake in Hangzhou and Caohai lake, dredging practice could effectively remove the polluted sediments, however, the critical dredging depth remains not fully confirmed yet. Simulating experiment in laboratory revealed that a dredging depth of 10 cm could make the quality of lake water ameliorate within a short period, and dredging practice of the depth more than 10cm seems unnecessary.Simulating experiment reveals that covering with red soil on sediment appears to be a prosperous practice to control eutrophication, by not only reducing the nutrient release from sediment, but also adsorbing algal and nutrients during the deposition process of red-soil.