School of Water Conservancy and Environment, University of Jinan, Jinan, 250022, China.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
Environ Geochem Health. 2020 Nov;42(11):3765-3778. doi: 10.1007/s10653-020-00638-8. Epub 2020 Jun 27.
The heavy metal contamination of the aquatic ecosystem is still prevalent even after reduction of the external anthropogenic inputs of the metals. The release of labile heavy metals from the sediments into the water is a potential risk, responsible for the contamination of the aquatic system. Herein, samples of sedimentary column cores were collected in Nansi Lake, and the distribution profiles of the labile and soluble metals (Cd, Cu, Ni, Pb, and Zn) were obtained by the diffusive gradient in thin films (DGT) and the high-resolution dialysis (HR-peeper) technique. Furthermore, the mobility, bioavailability and release risk of the heavy metals were assessed using the results of geochemical sequential extraction, DGT as well as the DGT-induced fluxes in sediments (DIFS) model. The results showed that the profile characteristics of the DGT-labile and soluble heavy metals showed irregular distribution in the sediment cores and Cd, Pb, Zn had an obvious positive correlation with Fe/Mn (p < 0.05). Ni, Cu, and Zn existed primarily in the residual fraction (accounting for 58-76%), while Cd and Pb existed in the reducible fraction (accounting for 50-67%). The Cd and Ni (0.027-0.185) had higher mobility coefficients compared with Pb, Cu, and Zn (0-0.011), and positive diffusive fluxes also proved that Cd and Ni were easy to be released from the sediments. In addition, the R values of five metals (0.18-0.85) ranged between R to 0.95, indicating that all the metals had partially sustained case from the sediments solid phase. Based on the DIFS model, the five metals had weak mobility from the sediment to pore water, but the release risks in the Nansi Lake should also be of concern, especially for the highly mobile Cd and Ni in the Dushan Lake.
即使减少了金属的外部人为输入，水生生态系统的重金属污染仍然普遍存在。底泥中不稳定重金属向水体中的释放是一种潜在的风险，会导致水生态系统的污染。本研究采集了南四湖柱状沉积物样品，利用扩散梯度薄膜（DGT）和高分辨率透析（HR-peeper）技术获得了可溶态和不稳定态金属（Cd、Cu、Ni、Pb 和 Zn）的分布特征。此外，还利用地化形态提取、DGT 以及 DGT 诱导的沉积物中通量（DIFS）模型评估了重金属的迁移性、生物可利用性和释放风险。结果表明，DGT 不稳定态和可溶态重金属的剖面特征在沉积物柱状样中呈不规则分布，Cd、Pb 和 Zn 与 Fe/Mn 呈显著正相关（p<0.05）。Ni、Cu 和 Zn 主要以残渣态存在（占 58-76%），而 Cd 和 Pb 主要以可还原态存在（占 50-67%）。Cd 和 Ni（0.027-0.185）的迁移系数高于 Pb、Cu 和 Zn（0-0.011），正的扩散通量也证明了 Cd 和 Ni 易于从沉积物中释放。此外，五种金属的 R 值（0.18-0.85）在 0.95 之间，表明所有金属均部分从沉积物固相中释放。基于 DIFS 模型，五种金属从沉积物向孔隙水中的迁移性较弱，但南四湖的释放风险也应引起关注，尤其是杜山湖中高迁移性的 Cd 和 Ni。
