水位波动驱动下Pb和Cd的迁移转化

The Migration and Transformation of Pb and Cd Driven by Water Level Fluctuations

摘要: 本研究通过室内动态土柱实验，模拟水位波动过程，系统探究了铅(Pb)和镉(Cd)在水位波动带中的迁移与转化行为。结果表明，水位波动通过改变氧化还原条件、pH值及吸附–解吸平衡，显著影响Pb和Cd的形态与迁移性。水位上升阶段，还原环境促进Pb和Cd的溶解与迁移；水位下降阶段，氧化环境则有利于其沉淀与固定。Pb的浓度峰值多出现在水位下降阶段，响应迅速；而Cd的响应滞后，在粗砂中峰值出现于水位上升阶段，在细砂中则延迟至下降或稳定后。不同粒径砂土对重金属的吸附能力差异显著，细砂对Pb和Cd具有更强滞留作用。水位波动速率通过调节水动力过程进一步影响重金属的释放与再分布。本研究为水位波动带重金属污染防控与生态修复提供了理论依据。

Abstract: This study investigated the migration and transformation behaviors of lead (Pb) and cadmium (Cd) in the water-level fluctuation zone through indoor dynamic soil column experiments. The results indicate that water level fluctuations significantly affect the speciation and mobility of Pb and Cd by altering redox conditions, pH values, and adsorption-desorption equilibria. During water level rise, the reductive environment promotes the dissolution and migration of Pb and Cd; during water level decline, the oxidative environment facilitates their precipitation and immobilization. The peak concentration of Pb generally occurred during the water level decline phase with a rapid response, while Cd exhibited a delayed response, with peaks appearing during the rise phase in coarse sand and further delayed in fine sand. The adsorption capacity varied significantly with soil texture, with fine sand showing stronger retention for both metals. The rate of water level fluctuation further influenced the release and redistribution of metals by modulating hydrodynamic processes. This study provides a theoretical basis for the control and ecological remediation of heavy metal pollution in water-level fluctuation zones.