Effect of landing disturbance caused by capping materials on the control efficiency of contaminated sediment capping.

Purpose: Fluid mud is highly disturbed during contaminated sediment capping when the settling velocity of the capping material is excessive. This study investigated how to reduce this disturbance in order to achieve better control efficiency. Materials and methods: Spherical, cubical, wafer-shaped, and sand materials were used as capping materials. The settling velocity, change in landing kinetic energy, and stable capping effect of the materials were studied through settling velocity, capping, and disturbance experiments. Results and discussion: Compared to other capping materials, the use of wafer-shaped materials significantly reduced the turbidity (expressed in nephelometric turbidity units (NTU)) and total phosphorus (TP) concentration in the overlying water after capping under both static and dynamic disturbance conditions. Conclusions: The results indicated that shaping capping materials into a wafer could effectively reduce the settling velocity and landing kinetic energy to reduce the disturbance of fluid mud during capping and achieve better control efficiency. [ABSTRACT FROM AUTHOR]