Immobilization of phosphorus (P) migrated from sediment increasing algal-available P pool in P-inactivating material

Use of phosphorus (P)-inactivating material to immobilize P released from sediment, typically under anoxic condition, is a method often considered to reduce lake internal P loading for eutrophication control. This study found that immobilizing the released P from sediment induced accumulation of algal-available P (NaHCO₃ and Fe oxide paper strip extractable P) in P-inactivating material which was even higher than those in raw sediment at initial stage (by 29.7% and 85.7%), although algal-available P substantially decreased in sediment after addition of the material and in the separated sediment from the mixtures. Given the possibility of exposing P-inactivating material to phytoplankton systems in overlying water typically during sediment resuspension, the accumulation suggested the potential of the resuspended material changing as P source for phytoplankton growth, increasing the uncertainties of sediment P immobilization method. Future work should focus more on the resuspension characteristics of P-inactivating material and on enhancing the capability of immobilizing algal-available P by the materials during internal P pollution control, especially in shallow lake.