Famous as the world cultural heritage, West Lake in Hangzhou city has plenty of soft sediments with high organic matter content. To search the countermeasures for internal phosphorus release reduction from the sediment, the sediment core incubation was conducted to understand the efficacy of Phoslock® on internal phosphorus release in spring, summer and winter, respectively. The results showed that the internal phosphorus release fluxes in winter and spring were relatively low, with averaged values in the entire lake of 0.13 mg·(m2·d)-1 and 0.29 mg·(m2·d)-1, respectively, while the release flux was 3.29 mg·(m2·d)-1 in summer, more than ten times higher than those in spring and winter. It was estimated that 23.7 kg of phosphorus could be released from sediment in the entire lake every day in summer. Spatially, the phosphorus release flux was related to organic matter contents in sediments, but not the phosphorus or bioavailable phosphorus contents in sediments in West Lake. With Phoslock® added at the rate of 630 g·m-2, sediment phosphorus release was successfully controlled, which reduced the phosphorus concentration in the lake water to less than 0.010 mg·L-1. Especially during summer time, the sediment phosphorus release was reduced by 98% after Phoslock® application. The research suggested that Phoslock® is powerful for phosphorus control even for sediments with high organic matter content, which could be considered in ecological restoration of WEst Lake.
Keywords: Phoslock®; West Lake; internal loading; phosphorus; sediment.