Cu/Pb/Zn/Cd在石英砂中的迁移实验及模拟

通过稳定流混合置换实验,研究了孔隙水流速和pH变化对Cu/Pb/Zn/Cd在石英砂中迁移行为的影响,获得了示踪剂Br-和Cu/Pb/Zn/Cd的穿透曲线(BTCs);并通过室内批量平衡实验获得吸附系数,进而计算出阻滞因子Rd。基于这些实验结果,借助CXTFIT2.1软件,用平衡CDE模型拟合了Br-的BTCs,得到了弥散系数D;在此基础上应用CDE非平衡模型拟合Cu/Pb/Zn/Cd在不同流速和pH条件下的BTCs,并预测了平行实验和不同埋深处Cu/Pb/Zn/Cd浓度的动态变化。结果表明,Cu/Pb/Zn/Cd的迁移能力随流速的增大而增强,而随pH的增大而降低;化学非平衡的两点模型能较好地模拟本文实验条件下Cu/Pb/Zn/Cd的迁移过程。

Modeling Cu/Pb/Zn/Cd transport in quartz sand column

Effects of pore-water velocity and pH on Cu, Pb, Zn and Cd transport in quartz sands were studied, through a stable flow miscible displacement experiment, and breakthrough curves(BTCs) of the tracer bromide(Br-) and Cu/Pb/Zn/Cd were obtained. And their adsorption coefficients were determined through indoors batch equilibrium experiments and then their retardation factors(Rd) were worked out. Based on the results of the experiments with the aid of Software CXTFIT2.1 (A nonlinear least-squares optimization approach) BTC of Br- was fitted with the equilibrium CDE model, yielding dispersion coefficient (D). On such a basis, BTCs of Cu, Pb, Zn and Cd in conditions of different pore-velocity and pH were fitted with the non-equilibrium CDE model, and dynamics of their concentrations at various depths and in parallel experiment were predicted. Results show that the transport of Cu/Pb/Zn/Cd in quartz sand columns increased with pore-water velocity, but decreased with rising pH. Conclusively, the non-equilibrium-theory-based two-site model describes better transport of Cu, Pb, Zn and Cd in such a scenario as of this experiment.