Effect of Zirconium-Modified Zeolite Addition on Migration and Transformation of Phosphorus in River Sediments Under Static and Hydrodynamic Disturbance Conditions

Abstract

In this study, the effect of the addition of zirconium-modified zeolite (ZrMZ) on the migration and transformation of phosphorus (P) in river sediments under static and hydrodynamic disturbance conditions was studied using sediment core incubation experiments. Results showed that, whether under static or hydrodynamic disturbance condition, the ZrMZ amendment suppressed the release of SRP from sediments into the overlying water. Furthermore, the addition of ZrMZ to the upper sediment (0-10 mm) not only resulted in the decrease of the dissoluble reactive P (SRP) concentration in the overlying water at a depth of 0-30 mm, but also led to the decrease of the diffusion flux of SRP from the pore water to the overlying water across the sediment-water interface (SWI). In addition, the ZrMZ amendment induced the transformation of the redox-sensitive P (BD-P) and HCl extractable P (HCl-P) into the metal oxide-bound P (NaOH-rP) and residual P (Res-P), thus resulting in the reduction of mobile P (sum of NH4Cl extractable P and BD-P) in the top 10 mm of sediment. In addition, the addition of ZrMZ into the top 10 mm of sediment resulted in reduction of the content of mobile P in 10-20 mm of sediment. Furthermore, the effect of ZrMZ addition on the migration and transformation of P in sediments under hydrodynamic disturbance condition had a certain difference from that under static condition. The presence of hydrodynamic disturbance enhanced the immobilization efficiency of SRP in the pore water at a depth of 0-20 mm by the ZrMZ amendment, and also increased the reduction efficiency of the SRP diffusion flux from the pore water to the overlying water across the SWI by the ZrMZ amendment. However, the efficiency of the control of SRP release from sediments to the overlying water by the ZrMZ amendment was slightly reduced by the hydrodynamic disturbance. The reductions of mobile P in the top sediment, SRP in the pore water as well as the diffusion flux of SRP from the pore water to the overlying water across the SWI played a key role in the control of SRP release from sediments to the overlying water by the ZrMZ amendment. Results of this work indicate that ZrMZ is a very promising amendment for the control of SRP release from river sediments under static and hydrodynamic disturbance conditions.