Study On Nitrogen And Phosphorus Release Of Sediments And The Control Of Water Lifting Aerator On Internal Pollution Of Zhoucun Reservoir

Zhoucun Reservoir is located in Shizhong District of Zaozhuang, Shandong Province, and it is an important water source of drinking water of Zaozhuang. Since early 1990 s, cage aquaculture lasted for nearly twenty years in Zhoucun Reservoir, and the eutrophication problem is serious. In recent years, the government has banned the aquaculture and the cages have been cleaned, resulting in the improvement of water quality. However, the large amounts of nutrients, which are accumulated in sediment,may release into overlying water under anaerobic condition, causing the deterioration of water quality, thereby leading to eutrophication. The samples in the typical positions of Zhoucun Reservoir were collected and measured in laboratory to study the nitrogen and phosphorus load, and also their species distributions were analyzed. The diffusion fluxes of nitrogen and phosphorus were calculated through the interstitial water diffusion model. Furthermore, the effect of water lifting aerator on control of sediment pollution release and the improvement of water quality were discussed. The main research results and conclusions are as follows:（1）The total nitrogen and total phosphorus contents of surface sediment in Zhoucun Reservoir are 3273-4870 mg·kg^-1 and 657-2279 mg·kg^-1 respectively, both exceed the lowest level which can cause ecotoxicity effects. The nitrogen and phosphorus in sediment have ecological risk, and there is a potential threat to the benthic communities and water quality. The nitrogen in sediment mainly consists of organic nitrogen, which accounts for 48% to 89% of total nitrogen. The major component of phosphorus is inorganic phosphorus, accounting for 79% to 89% of totalphosphorus. Al/Fe-P is the chief composition of inorganic phosphorus. The organic phosphorus and Al/Fe-P account for a high proportion of total phosphorus, reflecting Zhoucun Reservoir has a potential of phosphorus release.（2）The release fluxes of ammonia and dissolved inorganic phosphorus（DIP） are high in Zhoucun Reservoir, the fluxes of ammonia range from 216.47 mg·m^-2·a^-1 to5702.88 mg·m^-2·a^-1, the fluxes of dissolved inorganic phosphorus（DIP） range from18.37 mg·m^-2·a^-1 to 564.01 mg·m^-2·a^-1. The release fluxes of ammonia and DIP in thermal stratification period are higher than isothermally mixed period basically.（3）The operation results of water lifting aerator indicates that, the system achieves the desired effect. The system destructs the stratification and raises the oxygen in lower layer, and it shows effective control on nitrogen and phosphorus release from sediment to water, the concentration of ammonia and total phosphorus in water also decrease.