Zhang Zhi-Yong, Wan Cheng-Yan, Hu Hong-Qing, Yang Zhong-Hua, Yuan Yu-Jie, Zhu Wen
Key Laboratory of Ecological Impacts of Hydraulic-Projects and Restoration of Aquatic Ecosystem of Ministry of Water Resources, Institute of Hydroecology, Ministry of Water Resources and Chinese Academy of Sciences. Wuhan 430079, China.
College of Resource and Environment, Huazhong Agricultural University, Wuhan 430070, China.
Huan Jing Ke Xue. 2023 Feb 8;44(2):770-780. doi: 10.13227/j.hjkx.202203039.
The hydrological regime of rivers significantly changes after dam impoundment, which in turn affects the particle composition and heavy metal fractions of the river sediments. From June to July 2019, the sediments from 26 sampling sections were collected along the main stream of the Yangtze River from Panzhihua City in the upper reaches of the Yangtze River to Hukou City in the middle reaches of the Yangtze River. The concentrations and fractions of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn were measured using the BCR three-step extraction procedure. The pollution status and potential ecological risk of heavy metals in sediments were evaluated using the geo-accumulation index, the sediment quality guideline, and the risk assessment coding method (RAC). The results showed that the average particle size of sediments in the upper reaches of the Yangtze River (Jinsha River cascade reservoir section and the Three Gorges reservoir section) decreased from upstream to downstream, the total concentrations of As and Zn increased, and the variation trend in the middle reaches was not obvious. The content of clay particles was significantly positively correlated with the acid-soluble fraction concentrations of Cd and Ni. Cd was mainly in the residual fraction (59.26%) and acid-soluble fraction (24.67%). Large parts of Cr and Ni were residual fractions accounting for 92.41% and 83.41%, respectively. As, Co, Cu, Pb, and Zn were mainly in the residual fraction and the reducible fraction. The order of decrease for the pollution degree () of As, Cd, Co, Cr, Ni, and Zn was the Jinsha River, the middle reaches of the Yangtze River, and the Three Gorges Reservoir. The decrease order of bioavailability (RAC) of Cd, Co, Cr, Cu, Ni, and Zn was the Three Gorges Reservoir, the Jinsha River, and the middle reaches of the Yangtze River. The bioavailability of As and Pb decreased in the order of the middle reaches of the Yangtze River, the Three Gorges, and the Jinsha River. According to the classification of the RAC, Cd in the Three Gorges Reservoir area exhibited a high risk with the RAC accounting for 48.44%. Cu, Ni, and Zn showed a low or medium risk.
大坝蓄水后，河流的水文状况发生显著变化，进而影响河流沉积物的颗粒组成和重金属形态。2019年6月至7月，沿长江干流从长江上游的攀枝花市到长江中游的湖口市共采集了26个采样断面的沉积物。采用BCR三步萃取法测定了沉积物中砷、镉、钴、铬、铜、镍、铅和锌的含量及形态。利用地累积指数、沉积物质量基准和风险评估编码方法（RAC）对沉积物中重金属的污染状况和潜在生态风险进行了评价。结果表明，长江上游（金沙江梯级水库段和三峡水库段）沉积物平均粒径自上游向下游减小，砷和锌的总含量增加，中游变化趋势不明显。黏土颗粒含量与镉和镍的酸溶态含量显著正相关。镉主要存在于残渣态（59.26%）和酸溶态（24.67%）。铬和镍大部分为残渣态，分别占92.41%和83.41%。砷、钴、铜、铅和锌主要存在于残渣态和可还原态。砷、镉、钴、铬、镍和锌的污染程度（）由高到低依次为金沙江、长江中游和三峡水库。镉、钴、铬、铜、镍和锌的生物有效性（RAC）由高到低依次为三峡水库、金沙江和长江中游。砷和铅的生物有效性由高到低依次为长江中游、三峡和金沙江。根据RAC分类，三峡库区镉的RAC值为48.44%，呈现高风险。铜、镍和锌呈现低风险或中风险。
