Effect of Co-aging with Common Ions and Humic Acid on the Control of Phosphorus Release from Sediment by the Combination of Lanthanum-Modified Bentonite and Vallisneria natans

• • Co-aging with common ions and humic acid reduces the maximum phosphate adsorption capacity of lanthanum-modified bentonite by 33.8%, directly impairing its P-binding efficacy in natural waters. • • At an unaged LMB dosage of 89 g·m−2, the combination with Vallisneria natans achieves a 57.1% average reduction of SRP in overlying water and a 74.0% reduction of DGT-labile P in sediment, outperforming plant-only treatments. • • The combined treatment suppresses P release via two microbial pathways: dissimilatory iron(III) reduction and chemical reduction by sulfate-reducing bacteria metabolites, yet remains effective in reducing P flux to pore water and overlying water. • • Co-aging diminishes the combined technology's P control efficiency, underscoring the need to mitigate ion/HA interference for sustained sediment P immobilization in eutrophic water bodies.