Control of phosphorus release from sediment by nitrate-loaded ferrihydrite in the absence and presence of tetracycline input

This study investigated the efficacy and mechanisms of nitrate-loaded ferrihydrite (N-Fh) as an amendment and capping material in controlling internal phosphorus (P) loading from sediments, both with and without tetracycline (TC) input. Additionally, this study evaluated the microbiological safety of this technology. The results demonstrated that N-Fh displayed robust adsorption capabilities for phosphate (PO₄³^--P) and TC, with maximum adsorption capacities of 22.5 mg/g and 43.5 mg/g, respectively, at pH 7. The pre-loading of TC had only a minor inhibitory effect on PO₄³^--P adsorption by N-Fh. Regardless of TC input, N-Fh amendment, one-time capping, multiple capping, and fabric-wrapped capping were all effective in preventing P migration from sediment to overlying water (OW) under anoxic conditions. The immobilization of gradient diffusion in thin films (DGT)-labile P in the sediment was critical for inhibiting sedimentary P release into the OW. Analysis based on the Cluster of Orthologous Groups (COG) database revealed that N-Fh amendment and capping had minimal impact on bacterial community functions. Importantly, after N-Fh treatment, the bacterial communities retained their ability to perform essential ecological functions, which are vital for maintaining aquatic ecosystem health. These findings highlight the potential of N-Fh as a promising amendment and capping material for reducing the risk of sedimentary P release into OW. Furthermore, fabric-wrapped N-Fh capping emerges as a sustainable and effective strategy for mitigating internal P loading.