镉(Cd)影响地下水资源,对人类健康和环境构成严重威胁。它在地下水中的命运是复杂和具有挑战性的预测,因为它受到沉积物吸附的影响,与水相配体络合,和水力传导率的变化。在这项研究中,基于MODFLOW和RT3D的2D反应传输模型用于模拟已发表的镉迁移实验结果,该实验结果在包含高和低渗透区的流动池中不存在和存在EDTA(即,HPZ和LPZ)。然后将模型扩展到具有更复杂的LPZ配置的概念性流动池。模拟结果与实验数据基本吻合,对实验和模拟Cd废水浓度曲线的分析表明,相对于单独的水,EDTA增强了从LPZs中Cd的去除。模拟结果表明,较快的Cd去除是由于EDTA与LPZs中吸附的Cd络合,这增强了其溶解和随后的反向扩散。最后,模拟结果表明,随着LPZ异质性的增加,更多的Cd保留在流动池中,与单独的水相比,EDTA在增强Cd去除方面更有效;这些结果归因于更多的LPZ-HPZ界面,这些界面在污染期间增强了Cd向LPZ的传质,并增强EDTA向LPZs的传质,以促进清洁。总的来说,结果突出了使用EDTA从异质位点去除Cd的前景,但由于模型简单且缺乏对溶液pH值变化的考虑,建议谨慎。氧化还原电位,或竞争阳离子。
Cadmium (Cd) has impacted groundwater resources and can pose a serious threat to human health and the environment. Its fate in groundwater is complex and challenging to predict, as it is affected by adsorption to sediments, complexation with aqueous phase ligands, and variations in hydraulic conductivity. In this study, a 2D reactive transport model based on MODFLOW and RT3D is used to simulate published experimental results of cadmium migration without and with EDTA present in a flow cell containing high- and low-permeability zones (i.e., HPZs and LPZs). The model is then extended to conceptual flow cells with more complex LPZ configurations. Simulation results generally match the experimental data well, and analysis of experimental and simulated Cd effluent concentration profiles shows that EDTA enhances Cd removal from LPZs relative to water alone. Simulation results indicate that faster Cd removal is due to EDTA complexation with adsorbed Cd in LPZs, which enhances its solubilization and subsequent back diffusion. Lastly, simulation results show that with increasing LPZ heterogeneity more Cd is retained in flow cells, and EDTA is more effective in enhancing Cd removal relative to water alone; these results are attributed to more LPZ-HPZ interfaces that enhance Cd mass transfer into LPZs during contamination, and enhance EDTA mass transfer into LPZs to promote cleanup. Overall, the results highlight the promise of using EDTA to remove Cd from heterogeneous sites, but caution is advised due to model simplicity and lack of consideration of changes in solution pH, redox potential, or competing cations.