Inhibition of sediment erosion and phosphorus release by remediation strategy of contaminated sediment backfilling

The management of sediment-water interfaces, especially bed stability, is essential for controlling accumulated contaminants in the sediment. In this study, the relationship between sediment erosion and phosphorus (P) release under the remediation strategy of contaminated sediment backfilling (CSBT) was explored through a flume experiment, i.e. the dredged sediment was calcined into ceramsite after dewatering and detoxification and then backfilled to the dredged area for sediment capping, thus avoiding the introduction of foreign materials via in-situ remediation and the large-scale land occupation associated with ex-situ remediation. Acoustic Doppler velocimeter (ADV) and optical backscatter sensor (OBS) were used to measure the vertical distributions of flow velocity and sediment concentration in the overlying water, respectively, and diffusive gradients in thin films (DGT) was used to measure the P distribution in the sediment. The results revealed that improving bed stability from CSBT can considerably improve the robustness of sediment-water interface and reduce sediment erosion by more than 70%. The corresponding P release from the contaminated sediment could be inhibited with an inhibition efficiency as high as 80%. CSBT is a potent strategy for managing contaminated sediment. This study provides a theoretical reference for controlling sediment pollution, further supporting river and lake ecological management and environmental restoration.