沉积物再悬浮是影响沉积物重金属与周围水环境进行交换的一个重要进程，是贮存在沉积物中的金属污染物对水生生态系统造成危害的一个重要途径。而在这一进程中，颗粒态重金属的生物可利用性是如何变化的尚不明确。在前期的研究中，我们发现随着再悬浮时间的增加，沉积物中Zn的赋存形态由较为稳定的硫化态转化为较不稳定的碳酸盐及颗粒络合态。金属在沉积物中的赋存形态不同，理论上会具有不同的生物可利用性。据此我们提出假设：在沉积物再悬浮过程中，沉积物金属的生物可利用性也是随悬浮时间逐渐增加的。本项目拟采用稳定同位素生物反标法，结合沉积物金属的地球化学形态分析，阐明颗粒态重金属生物可利用性在沉积物再悬浮这一进程中的变化规律。稳定同位素生物反标法避免了过往研究中使用的沉积物直接标记示踪技术不能准确反映沉积物与金属结合方式这一缺点，从而为预测重金属的生物毒性效应及生态风险评估提供更可靠的科学依据。

Sediments serve as an important sink for metal contaminants in aquatic system. But the metals are not permanently sequestered in it, but instead they are experiencing dynamic exchange with the ambient aquatic environment. Sediment resuspension mobilizes sediment particles, as well as the associated metals, and poses potential hazards to the aquatic ecosystem. Understanding the dynamic change of bioavailability of sediments bound metals during this process is key to predict the associated adverse effects. In our previous study, we quantified the temporal evolution of metals speciation in suspended sediments during resuspension and found most Zn initially existed as ZnS and was gradually converted to Zn-CO3 and Zn surface complexes with resuspension time. Theoretically, metal speciation could partially reflect the bioavailability of metals, we therefore hypothesize that the bioavailability of metals also increases with resuspension time. This project proposes to utilize stable isotope inverse labeling methods, combined with the metal speciation analysis, to study the effects of resuspension on bioavailability of metals. This novel method will avoid the disadvantage that normal labeling and tracing methods possess and therefore the study will provide as valid scientific basis for the assessment of ecotoxicity of metals.