Phosphorus sorption to suspended sediment in freshwater

The effect of flow transport on phosphorus sorption to suspended sediment was investigated by combining field experiments with indoor experiments. The phosphorus distribution was found to be spatially variable and the phosphorus concentration gradient between pore water and overlying water decreased with sediment resuspension in the Huaihe River. Indoor experiments were conducted in a batch reactor and an elongated flume. Flow transport accelerated phosphorus sorption onto suspended sediment and the time to reach quasi-equilibrium decreased with an increase in flow velocity in dynamic water. Both phosphorus sorption amount and sorption rate were affected by the flow velocity, the initial phosphate concentration and suspended sediment concentration. The influence of flow velocity on phosphorus sorption amount was found to be controlled by the variance of the initial phosphate concentration. When compared with other isothermal adsorption models, the Langmuir equation provided the best description of the phosphorus sorption performance of the hydrodynamic experiments. Adsorption and desorption were not exactly equal, and the phosphorus sorption amount fluctuated with time in a quasi-equilibrium state in the flume experiments.