State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China; Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China.
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
Sci Total Environ. 2022 Nov 25;849:157882. doi: 10.1016/j.scitotenv.2022.157882. Epub 2022 Aug 6.
Geochemical behaviors of trace metals in the sediment profiles are crucial for predicting the associated environmental risks in aquatic ecosystems. However, the comprehensive transport of trace metals under both equilibrium and dynamic conditions is still unclear under the changing hydrological regime. Here, the equilibrium partitioning behaviors and remobilization of five trace metals (Ni, Cu, Zn, As, and Pb) in sedimentary profiles within the tributaries of the Three Gorges Reservoir were explored by the partitioning coefficient (K), diffusive gradients in thin films (DGT), and DGT induced flux in sediments (DIFS) model. According to the K values, As posed the highest migration ability among the trace metals in the sediment profiles under equilibrium circumstances. Similarly, the dynamic processes of trace metals simulated by the DIFS model also suggested that As displayed the highest desorption rate despite having the lowest labile pool size. Moreover, all trace metals were classified as the "partially sustained" case, while the supply abilities of As and other trace metals were limited by the diffusion and the desorption kinetics, respectively. In addition, DGT-labile trace metals showed a diffusion trend from the sediment to the water column (except for Zn) at the sediment-water interface, indicating potential risks to water quality. Specifically, the equilibrium partitioning behaviors revealed the potential labile pool of trace metals in the solid phase, and the dynamic resupply process between the solid phase and porewater remained undetermined. In comparison, although DGT simulated the kinetic process of trace metals in the sediments, the labile pool of the trace metals could not be obtained. This study provided a holistic insight into the complementary trace metal behaviors under both equilibrium and dynamic conditions in the sediment and was beneficial to the water quality protection and internal pollution remediation in the aquatic environment.
痕量金属在沉积剖面中的地球化学行为对于预测水生生态系统中相关的环境风险至关重要。然而，在水文变化的情况下，平衡和动态条件下痕量金属的综合传输仍不清楚。在这里，通过分配系数（K）、薄膜扩散梯度（DGT）和 DGT 诱导的沉积物通量（DIFS）模型，研究了三峡水库支流沉积物剖面中五种痕量金属（Ni、Cu、Zn、As 和 Pb）的平衡分配行为和再迁移。根据 K 值，在平衡条件下，As 在沉积剖面中的痕量金属中具有最高的迁移能力。同样，DIFS 模型模拟的痕量金属动态过程也表明，尽管 As 的不稳定库最小，但它具有最高的解吸率。此外，所有痕量金属均被归类为“部分维持”情况，而 As 和其他痕量金属的供应能力分别受到扩散和解吸动力学的限制。此外，DGT 不稳定的痕量金属在沉积物-水界面处表现出从沉积物向水柱状扩散的趋势（除 Zn 外），表明对水质存在潜在风险。具体来说，平衡分配行为揭示了固相中痕量金属的潜在不稳定库，而固相和孔隙水之间的动态补给过程仍不确定。相比之下，尽管 DGT 模拟了沉积物中痕量金属的动力学过程，但无法获得痕量金属的不稳定库。本研究为了解沉积相中的痕量金属在平衡和动态条件下的互补行为提供了一个整体视角，有助于保护水生态环境的水质和内部污染修复。
