Abstract: After external pollutant discharge is reduced, release of contaminant from sediment to overlying water may cause contamination to the river and lake again. The mechanism of contaminant release through the sediment-overlying water interface is studied under the condition that the overlying water flow does not lead to sediment suspension. The overlying water flow is calculated using the k-ε turbulence model. The sediment is regarded as an isotropic homogeneous porous medium. Therefore the seepage field in the porous sediment layer is obtained by solving the Darcy’s aligns. Several two dimensional coupled steady flow fields of the overlying water and the pore water in the sediment are calculated. Based on the flow fields obtained, the unsteady contaminant solute transportation process in the sediment and the overlying water is numerically simulated, with the shapes of the sediment-overlying water interface being flat or periodic triangular respectively. Numerical results show that exchange of the pore water and the overlying water is an important factor that decides the release flux of contaminant from the sediment to the overlying water.

Key words: contaminant, numerical simulation, release, sediment-water interface