Hydrodynamic effects on contaminants release due to rususpension and diffusion from sediments
2013
ZHU, Hong-wei | CHENG, Peng-da | ZHONG, Bao-chang | Wang, Dao-zeng
Hydrodynamic effects play a very important role in the contaminants release from sediments. Experiments were performed to study contaminants releasing characteristics due to resuspension. The time-dependent variation of COD concentration and relative roles under static and dynamic state of the overlying water were analyzed. Experimental results showed that COD concentration in the water column got a striking increment on the dynamic conditions, mainly by reducing the thickness of concentration boundary layer near sediment-water interface and destructing the surface structure of sediment. Hydrodynamics increased contaminants release rates and flux in unit time. Before reaching an equilibrium stage, the dynamic release caused by the resuspension was more effective than static one due to molecular diffusion. The release rate of COD increased with flow velocity and decreased with water depth. But at a shallow water depth, wave effects would dominate the causing resuspension, resulting in contaminants release in large quantity. The intensity of pollutant release increased with time in a rather circuitous process. The diffusion of pollutant from internal sediment to the sediment-water interface would maintain the endogenous release effects.
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