State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100038, China; Department of Water Environment, China Institute of Water Resources and Hydropower Research, Beijing 100038, China.
State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100038, China; Department of Water Environment, China Institute of Water Resources and Hydropower Research, Beijing 100038, China.
Sci Total Environ. 2019 Jan 15;648:197-205. doi: 10.1016/j.scitotenv.2018.08.112. Epub 2018 Aug 9.
Response of trace metals to the consecutive water level fluctuation in the Three Gorges Reservoir (TGR) sediments remains unclear. Here, we evaluated the influence of consecutive stages of water level fluctuation on trace metal pollution using multiple analytical approaches. The spatio-temporal distributions of trace metals in TGR sediments were investigated for five consecutive water impoundment stages from 2015 to 2017. Anthropogenic contributions and trace metal stocks in the TGR were quantitatively estimated using a combination of a regional geochemical baseline (RGB) and annual sediment load. Results showed that trace metals were accumulated after the construction and impoundment of the TGR. However, after the TGR operated normally for more than five years, trace metals concentrations stabilized in sediments. Trace metal concentrations in the mainstream were slightly higher than those in the tributaries. In the mainstream, metal concentrations in the upstream were lower than those in the midstream and downstream except for Cd. Anthropogenic contributions of trace metals ranged from 8.51 to 24.86% and were highest for Hg and Cd. The sediment load was the main factor influencing trace metal stock in TGR sediments. Although the total Cd stock amount was relatively low, its potential ecological effects are of great concern due to its high mobile fraction percentages and toxicity. The RGB-based geo-accumulation index and potential ecological risk index showed that TGR sediments were uncontaminated, and were subject to low ecological risk from trace metals. This result differs from traditional assessment results, indicating that previous assessments may overestimate the ecological risks of the trace metals in the TGR. The health risks posed by trace metals bio-accumulated in fish, stemming from sediment resuspension, were assessed using an environmental impact assessment model. Results suggested that residents should not experience significant health risks from the intake of individual metals through fish consumption.
三峡水库（TGR）沉积物中痕量金属对连续水位波动的响应仍不清楚。在这里，我们使用多种分析方法评估了连续水位波动阶段对痕量金属污染的影响。我们研究了 2015 年至 2017 年五个连续蓄水阶段 TGR 沉积物中痕量金属的时空分布。利用区域地球化学基线（RGB）和年沉积物负荷的组合，定量估计了 TGR 中人为贡献和痕量金属储量。结果表明，TGR 建成蓄水后，痕量金属得到了积累。然而，在 TGR 正常运行五年多后，沉积物中的痕量金属浓度稳定下来。主流中的痕量金属浓度略高于支流中的浓度。在主流中，除 Cd 外，上游的金属浓度低于中游和下游。痕量金属的人为贡献范围为 8.51%至 24.86%，Hg 和 Cd 的人为贡献最高。沉积物负荷是影响 TGR 沉积物中痕量金属储量的主要因素。尽管总 Cd 储量相对较低，但由于其高移动分数百分比和毒性，其潜在生态效应令人关注。基于 RGB 的地积累指数和潜在生态风险指数表明，TGR 沉积物未受污染，且受痕量金属的生态风险较低。这一结果与传统评估结果不同，表明先前的评估可能高估了 TGR 中痕量金属的生态风险。利用环境影响评估模型评估了因沉积物再悬浮而导致生物积累在鱼类中的痕量金属对健康的风险。结果表明，居民通过鱼类摄入个别金属不会遭受显著的健康风险。
