不同氧化还原条件下土壤中Cd/Zn/Cu共运移特征及数值模拟

以重金属离子镉（Cd）、锌（Zn）、铜（Cu）为研究对象，通过室内土柱混合置换实验和数值模拟方法，分析了5种不同氧化还原电位（E_h）对Cd、Zn、Cu在土壤中运移的影响.结果表明，不同E_h下，Cu的竞争吸附能力均大于Cd和Zn，移动性较小；并产生了“滚雪球效应”，导致出流液中Cd和Zn的浓度大于输入浓度.与原土相比，E_h的增加或降低均促进了Zn、Cd的迁移速率，但对实验周期内回收率的影响不同；E_h的增加促进了Cu的迁移.两点非平衡模型（TSM）和单点非平衡吸附模型（OSM）较好地模拟了重金属的迁移，且进一步表明了土壤对重金属的吸附受吸附反应速率的限制（f<0.7）.在复合污染土壤评价和防治中，不仅要考虑E_h的影响，还要关注由竞争吸附所产生的浓度叠加效应，避免低估重金属的污染风险.

Characteristics and numerical simulation of the co-transport of Cd/Zn/Cu in soils under different redox potentials

The column experiments and numerical simulations were conducted to evaluate effects of redox potentials (Eh) on the transport of cadmium (Cd), zinc (Zn), and copper (Cu) in soils. The results showed that the competitive adsorption capacity of Cu was greater than that of Cd and Zn, resulting in a lower mobility in the soil under different redox potentials. Due to the competitive adsorption of Cd, Zn, and Cu, the "snow plow effect" takes place, resulting in the higher concentrations of Cd and Zn in the effluents than in the input. Compared to the control, both the increase and decrease in Eh promote the transport rate of Zn and Cd, but have different impacts on recovery rate. With an increase in Eh, the transport of Cu can be promoted in the soil. The good performance of TSM and OSM models for simulating the transport behavior of heavy metals further confirms that the adsorption of heavy metals in soils is time-limited (f < 0.7). In general, both the influence of redox potential and the concentration superimposition caused by heavy metal competitive adsorption should be considered in the evaluation and prevention of heavy metal compound contaminated soils.