Particle size-related vertical redistribution of phosphorus (P)-inactivating materials induced by resuspension shaped P immobilization in lake sediment profile

Lake geoengineering with phosphorus (P)-inactivating materials to reduce sediment P loading is often used for eutrophication control. The redistribution of materials in sediment, especially those induced by resuspension, is reportedly a common phenomenon during practical applications, which may interfere with the pollution control. Notably, a recent study by the authors initially found that the heterogeneous properties of materials and sedi-ments varied the P immobilization in different sized sediments which exhibited diverse movement characteris-tics. Therefore, this study hypothesizes a particle size-related vertical redistribution of materials in the sediment profile induced by resuspension, which shapes sediment P immobilization at different depths. Based on two differently sized materials, lanthanum (La)-modified bentonite clay (Phoslock) and drinking water treatment residue (DWTR), this study found a weakened reduction of mobile P and bioavailable P pool by both DWTR and Phoslock in surface sediment after resuspension. As the depth decreased from 8 mu m fraction), which tended to become enriched in surface sediment after resuspension, while relatively large materials (e.g., 63 mu m fraction) regulated their redistributions and were more likely to be buried at the bottom of the sediments. Accordingly, to design appropriate strategies for lake geoengineering, relatively small materials (e.g., <8 mu m) targeting to immobilize both mobile and bioavailable P are typically recommended to be developed for restoration of lakes with frequent sediment resuspension.