Abstract
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•Calcium silicate hydrates (CSH) are highly effective for immobilizing P in sediment.•CSH convert Fe-P to Ca-P and Ex-P, inhibiting P release from sediment.•CSH amendment method – capping or mixing, had marginal effect on P release.•Macrophytes showed less effect on P immobilization and speciation than CSH.
Phosphorus released from sediment is the main source of endogenous phosphorus for lake eutrophication. Calcium silicate hydrates (CSH) have been demonstrated effective for phosphorus removal as sediment amendment, however, macrophytes in lakes may have ambiguous impacts on phosphorus release and immobilization. In this study, effects of CSH amendment coupled with aquatic plants, Myriophyllum spicatum, on the removal of phosphorus in lake sediment were investigated. During 50days batch experiment, the amount of phosphorus released to the overlying water was inhibited by 90% at CSH dosage of 100g·kg−1 (mixing with sediment) as compared to the phosphorus released from the sediment without CSH, and the average soluble reactive phosphorus in overlying water decreased from 0.2 to 0.028mg·L−1. After 35days operation, the amounts of Ca-P and exchangeable-P in sediments increased by 4.9% and 11.6%, respectively, while Fe-P decreased by 17.4%. CSH had predominant effect on phosphorus removal and speciation than plants. However, plants uptake bioavailable phosphorus as nutrition, thereby reducing phosphorus in sediment. The amount of phosphorus in plants with CSH after 35days was 1.76 times of the plants grown in the sediment without CSH, and the growth rate of plants (dry weight) with CSH was 1.18 times of those grown in sediments without CSH.