Numerical simulation of phosphorus release from resuspended sediment
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RESEARCH PAPER
Numerical simulation of phosphorus release from resuspended sediment Pengda Cheng1 · Xinquan Wang1,2 · Chun Feng1 Received: 29 April 2020 / Revised: 8 July 2020 / Accepted: 8 July 2020 / Published online: 11 November 2020 © The Chinese Society of Theoretical and Applied Mechanics and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract One of the main issues in environmental hydraulics is pollutant release from sediments. For instance, the strong affinity between phosphorus and sediment permits most of the phosphorus to be adsorbed on the surface of the sediment particles in rivers or lakes. Post sediment resuspension, phosphorus is desorbed from the sediment to the overlying water. The release of phosphorus from the resuspended sediment is an important process in the secondary pollution of water. Herein, a coupled mechanical model of the overlying water, sediment, and pollutant was established based on the experimentally gathered data. Two types of sediment with different adsorption and desorption characteristics were selected to simulate the process of sediment resuspension and phosphorus release under different hydrodynamic conditions. The simulation results were subsequently used to analyze the relationship between the flow field characteristics and phosphorus concentration, from which the relationships between velocity, particle volume fraction, turbulent kinetic energy, total phosphorus concentration, desorbed phosphorus concentration, and time were elucidated. Based on the results, phosphorus is rapidly released into the overlying water from the resuspended sediment, and it reaches a peak value in a short duration. Unlike the release process of non-adsorption pollutants, hydrodynamic conditions and sediment properties play a crucial role in the phosphorus release process. The turbulent kinetic energy rapidly increases with the flow velocity, whereas the desorbed phosphorus concentration exhibits a certain relationship with the particle volume fraction and turbulent kinetic energy. In particular, the turbulent kinetic energy increases the desorbed phosphorus concentration per unit time. Additionally, the time taken by the total phosphorus concentration to attain its peak value is closely related to the characteristics of the flow field, whereas the amount of phosphorus is closely related to sediment properties. Post sediment resuspension, the release of phosphorus shows the characteristics of a centralized and massive release, which suggests that the total phosphorus concentration in the overlying water would change in a short duration and cause secondary pollution in the water environment. Keywords Resuspended sediment · Adsorption · Desorption · Turbulent kinetic energy · Phosphorus
1 Introduction Considered to be a natural complex, a water body comprises several elements: water, soluble substances, resuspended substances, aquatic organisms, and sediment [1]. Pollutants entering the water body deposit sediment that accumulates over time to form a thick sediment layer containin
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