Comparison of efficacy of two P-inactivation agents on sediments from different regions of Lake Taihu: sediment core incubations

Lake Taihu, the third largest shallow freshwater lake in China, has experienced massive algal blooms caused by nutrient loading. Sediment capping experiments were undertaken to assess the efficacy of two P-inactivation agents (Algalblock and Phoslock) to reduce internal phosphorus loading. Intact sediment cores were collected from three sites in Lake Taihu, which represent different trophic states and ecological types of lake. The experiments were carried out for 60 days and yielded the following findings: (1) Phoslock has a higher efficiency than Algalblock at blocking P release from sediment. (2) The efficiencies of both the P-inactivation agents are related to the dosage (range, 100 –1000g/m2) of agents in the different regions. In Dapu and Meiliang where there is a higher P content in the sediment, the 1000g/m2 treatment of both Algalblock and Phoslock had the highest P-removal efficacy. In Eastern Taihu Bay where there is a higher organic matter content, the 1000g/m2 dosage of Phoslock had the highest P-removal efficacy compared to other dosage levels, whilst the 100 g/m2 dosage of Algalblock had the highest efficacy. (3) Both agents had problematic side effects, with the potential to alter the microbial processes of coupled nitrification and denitrification and also to induce active element leaking from agents.Yanqing Ding, Boqiang Qin, Hai Xu, Baili Dong and Justin D. Brooke