Physicochemical effects of calcium on suppression of coastal sediment resuspension

The coastal in-situ capping method can sequester contaminated sediment and suppress sediment resuspension. Few studies have investigated the suppression of sediment resuspension induced by calcium eluted from in-situ capping materials. We investigated the physicochemical suppression of calcium on sediment resuspension. A resuspension experiment was conducted in an annular flume using coastal sediment mixed with 0 g (CSM0), 1 g (CSM1), 5 g (CSM5), and 10 g (CSM10) of Ca(OH)2 under a stepwise increase in bottom shear stress. Calcium enhanced sediment erosion resistance, decreasing suspended sediment concentrations. Exponentially increased SSC in CSM0 and CSM1 was three times higher than that in linearly increased CSM10. Viscosity in CSM10 was approximately three times higher than that in CSM0 and CSM1. Calcium-induced cation exchange increased sediment viscosity via sediment structural rearrangement, calcium-silicate-hydrate production, and the development of larger aggregates. Consequently, calcium suppressed sediment resuspension by physiochemically changing the sediment properties. •Effects of calcium on coastal sediment resuspension suppression were investigated.•Suspended sediment flux decreased by increased calcium concentration in sediment.•Calcium effectively enhanced erosion resistance of surface and mass erosion.•Cation exchange induced by calcium increased density and viscosity of sediment.