Gao Li, Zhuo Haihua, Xu Dongyu, Qian Bao, Gao Bo
State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100038, China; North China Power Engineering CO., LTD of China Power Engineering Consulting Group, Beijing 100120, China.
Changjiang Basin Ecology and Environment Monitoring and Scientific Research Center, Changjiang Basin Ecology and Environment Administration, Ministry of Ecology and Environment, Wuhan 430010, China.
Sci Total Environ. 2024 May 1;923:171289. doi: 10.1016/j.scitotenv.2024.171289. Epub 2024 Feb 27.
The construction and operation of the Three Gorges Dam occluded sediment transportation in the Yangtze River. However, the sources, transport processes, and environmental impacts of these sediments on the Three Gorges Reservoir (TGR) remain unclear. Here, we used rare earth elements (REEs) to trace the transport pathways of sediments in the TGR, China. Geochemical characteristics including the chemical composition and fractionation, temporal and spatial distribution, and potential sources of REEs were also evaluated in this study. The individual REEs concentration in the TGR sediments followed the Oddo-Harkins rule, with the mean REEs value of 207.33 μg/g. REEs concentrations in the midstream were higher than those in the upstream and downstream of the TGR. Statistical analysis showed that water impoundment phase had no significant influence on the distribution of REEs. TGR sediments are mainly derived from terrigenous detrital particulates, characterized by a distinctive enrichment in light REEs, with its percentage higher than 90 % of the total REEs. The significant positive correlation among the REEs confirmed that they are co-existed and shared the similar sources. Multiple provenance analysis approaches using discriminant function analyses, provenance indices, and La/Yb-La/Sm-Gd/Yb ternary diagrams further indicated that the REEs in sediments originated from the weathering of mudstone in the basin of TGR. After periodic water level fluctuation for more than six years, the chemical compositions of REEs in TGR sediments slightly differed from those of the Yangtze River sediments before TGR construction, but were similar to those of the downstream of the Yangtze River. Therefore, this study indicated that the construction and operation of the TGR changed the chemical compositions and the origin of the sediments in the Yangtze River, which can provide useful insights into the transport pathways of TGR sediments and their impacts on the fluvial environment.
三峡大坝的建设与运行阻断了长江的泥沙输移。然而，这些泥沙的来源、输移过程及其对三峡水库（TGR）的环境影响仍不明确。在此，我们利用稀土元素（REEs）来追踪中国三峡水库泥沙的输移路径。本研究还评估了REEs的地球化学特征，包括化学成分与分馏、时空分布以及潜在来源。三峡水库沉积物中各REEs浓度遵循奥多-哈金斯规则，REEs平均值为207.33μg/g。三峡水库中游的REEs浓度高于上游和下游。统计分析表明，蓄水阶段对REEs的分布没有显著影响。三峡水库沉积物主要来源于陆源碎屑颗粒，其特征是轻REEs显著富集，其百分比高于REEs总量的90%。REEs之间显著的正相关证实它们共存且来源相似。利用判别函数分析、物源指数和La/Yb-La/Sm-Gd/Yb三元图等多种物源分析方法进一步表明，沉积物中的REEs源自三峡水库流域泥岩的风化。经过六年多的周期性水位波动后，三峡水库沉积物中REEs的化学成分与三峡大坝建设前长江沉积物的化学成分略有不同，但与长江下游的相似。因此，本研究表明三峡大坝的建设与运行改变了长江沉积物的化学成分和来源，这可为三峡水库沉积物的输移路径及其对河流环境的影响提供有益的见解。
