YUE Kaikai, DENG Bing, HE Rong, QU Jianguo

(State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China)

Abstract: Nineteen suspended sediment samples from the mainstream and seven suspended sediment samples from tributaries were collected in the middle and lower reaches of the Yangtze River during the dry season (January, 2008), Rare Earth Elements (REEs) in these samples were characterized to discuss the influences, including composition and provenance changes, of sediment retention by the Three Gorges Reservoir (TGR). The results show that: the coefficient of variation (CV) of REEs in suspended sediments between Yichang and Chenglingji were significantly greater than that of after Chenglingji, and obvious anomalies of Eu and Ce occurred at some sites between Yichang and Chenglingji, suggesting that sediment compositions changed significantly by the TGR. REEs characteristics in sediments of the Dongting Lake inherited those of mainstream Yangtze River. In terms of the sediment provenance, the Poyang Lake and the Hanjiang River contributed respectively about 58% and 23% sediment of the mainstream during the observation period. All above results indicated that the provenance and composition of suspended sediments in the middle and lower reaches of the Yangtze River were changed due to the sediment retention of the TGR. It is to say that, downstream of the TGR, the riverbed erosion occurred significantly and sediment contributions from downstream tributaries to the Yangtze River increased.

Key words: Rare Earth Elements; suspended sediment; the Three Gorges Reservoir; riverbed erosion; sediment provenance

EARTH AND ENVIRONMENT Vol.46, No.3, Tot No.323, 2018, Page 288-295