Sedimentation and associated trace metal enrichment in the riparian zone of the Three Gorges Reservoir, China.
Sedimentation and associated trace metal enrichment in the riparian zone of the Three Gorges Reservoir, China.
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DOI：
10.1016/j.scitotenv.2014.01.122
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发表时间：
2014-05
期刊：
影响因子：
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通讯作者：
Q. Tang;Y. Bao;Xiu-bin He;Huaidong Zhou;Z. Cao;P. Gao;Rong-hua Zhong;Yun-hua Hu;Xin-bao Zhang-Xin-bao-Z
中科院分区：
文献类型：
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作者：
Q. Tang;Y. Bao;Xiu-bin He;Huaidong Zhou;Z. Cao;P. Gao;Rong-hua Zhong;Yun-hua Hu;Xin-bao Zhang-Xin-bao-Z
三峡水库蓄水形成了垂直高度30米、总面积349平方公里的人工河岸带，因水库定期蓄水和自然洪水的发生，出现季节性淹没和裸露。水文情势的显著变化导致了许多环境变化。本研究调查了河岸带典型地段的沉积和金属丰度的大小和空间格局，并探讨了它们与变化的水文状况之间的联系。特别是，我们测量了总沉积物深度，并收集了表层河岸沉积物和下剖面河岸土壤(每隔5厘米)用于痕量金属的测定。分析表明，年平均沉积速率变化范围为0.5~1000万cm·−-1，且随海拔升高而显著降低。这种横向分布主要归因于水位和悬浮泥沙浓度的季节性变化。在河岸沉积物和土壤中都发现了痕量金属的富集量，但河岸沉积物中的含量普遍高于河岸土壤中的含量，且呈类似的横向递减趋势。金属污染评价结果表明，河岸带沉积物中镍、锌、铅为轻度污染，铜为中度污染，镉为中度至重度污染；河岸带土壤为砷轻度污染，镉为中度污染。河岸沉积物中痕量金属的富集可能是由于上游人为来源的污染沉积物的外部输入，以及在纯泥沙动员过程中和水库蓄水导致的长时间洪泛期后溶解部分的化学吸附所致。
Impoundment of the Three Gorges Reservoir has created an artificial riparian zone with a vertical height of 30 m and a total area of 349 km2, which has been subjected to seasonal inundation and exposure due to regular reservoir impoundment and the occurrence of natural floods. The significant alteration of hydrologic regime has caused numerous environmental changes. The present study investigated the magnitude and spatial pattern of sedimentation and metal enrichment in a typical section of the riparian zone, composed of bench terraces with previous agricultural land uses, and explored their links to the changed hydrologic regime. In particular, we measured the total sediment depths and collected surface riparian sediments and down-profile sectioned riparian soils (at 5 cm intervals) for trace metal determination. Our analysis showed that the annual average sedimentation rates varied from 0.5 to 10 cm·yr− 1and they decreased significantly with increasing elevation. This lateral distribution was principally attributed to seasonal variations in water levels and suspended sediment concentrations. Enriched concentrations of trace metals were found both in the riparian sediments and soils, but they were generally higher in the riparian sediments than in riparian soils and followed a similar lateral decreasing trend. Metal contamination assessment showed that the riparian sediments were slightly contaminated by Ni, Zn, and Pb, moderately contaminated by Cu, and moderately to strongly contaminated by Cd; while riparian soils were slightly contaminated by As, and moderately contaminated by Cd. Trace metal enrichment in the riparian sediments may be attributed to external input of contaminated sediments produced from upstream anthropogenic sources and chemical adsorption from dissolved fractions during pure sediment mobilization and after sink for a prolonged flooding period due to reservoir impoundment.