底泥-上覆水界面污染物释放机制的数值模拟

当外源污染受到控制后, 河流与湖泊底泥中的污染物可能会引起上覆水的再次污染. 在上覆水流动不致底泥起动悬浮的条件下, 数值模拟了底泥中污染物在底泥-上覆水界面向上覆水释放的机制. 采用k-ε模型计算了上覆水的湍流流动, 并采用 Darcy 定律描述了多孔介质中的渗流, 这里底泥被看成是各向同性均匀多孔介质; 耦合计算了上覆水和底泥中孔隙水的定常流动, 并基于流场计算结果, 数值计算了非定常溶质迁移扩散过程; 数值研究了平整底泥-上覆水界面以及底泥-上覆水界面为周期性三角状时, 污染物由底泥向上覆水释放的规律. 研究结果表明, 底泥中孔隙水与上覆水的交换是决定底泥中污染物向上覆水释放量的重要因素.

Numerical Simulation on Mechanism of Contaminant Release Through Sediment-Overlying Water Interface

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.