Environmental quality of Xuanwu Lake, China, after restoration

Abstract Some restoration measures were implemented in Xuanwu Lake to control water eutrophication, including sediment dredging, algal bloom control through clay flocculation, and the growth of aquatic macrophytes. The water quality of Xuanwu Lake was monitored before and after the restoration. The results showed that the sediment was not the primary pollution source of the water body, the dredging did not change the nutrient contents in the lake significantly, and the heavy metal content in the sediment also did not decrease significantly. Therefore, sediment dredging should be carefully selected; otherwise, aquatic ecosystems may be damaged, and exogenous pollution will become severe. It is necessary to restore aquatic plants after dredging. The water quality improved with increased water diversion and improved less when it exceeded a certain level. The volume of water diversion should be controlled at an appropriate level. Clay flocculation effectively inhibited cyanobacterial blooms within a short time, improved water quality, and promoted the restoration of the Potamogeton crispus population. Clay flocculation is an effective way to control water eutrophication under emergent conditions. In addition, water quality was improved distinctly during the growing period of the P. crispus population, compared to when aquatic vegetation was minimal. Aquatic population restoration is a sustainable and effective approach for managing Xuanwu Lake and controlling water eutrophication.