Yangtze River Mainstream Research Articles

Strontium isotopic compositions of dissolved and suspended loads from the main channel of the Yangtze River

The concentrations of Sr and 87Sr/ 86Sr isotopic ratios have been measured in the dissolved loads from the main channel of the Yangtze River. The result shows that the Yangtze River mainstream water has considerably higher Sr concentration (202–330 μg kg −1) and slightly lower 87Sr/ 86Sr ratio (0.7098–0.7108) than the global average runoff values of dissolved Sr (78 μg kg −1) and 87Sr/ 86Sr ratio (0.7119). The 87Sr/ 86Sr values of 0.7098–0.7108 in river waters result from the intense weathering of carbonate and evaporate rocks that enriched in the Yangtze River drainage basin. The calculated result based on the end-member mixing model shows that about 91% of total dissolved Sr are derived from the weathering of carbonate and evaporate rocks and the other 9% derived from the weathering of silicate rock. The Yangtze River transports about 1.86 × 10 11 g yr −1 (2.12 × 10 9 mol yr −1) of dissolved Sr annually to the East China Sea, with an average 87Sr/ 86Sr of 0.7108. The calculated “ 87Sr excess flux” of the Yangtze River is about 2.12 × 10 7 mol yr −1, indicating the important impact on seawater Sr isotope evolution. The measured 87Sr/ 86Sr ratios of suspended particulate matters in the Yangtze River water ranging from 0.7178 to 0.7252, are about 0.015 higher than that of corresponding dissolved loads, reflecting more important contribution of silicate particles in suspended particulate matters and preferential dissolution of carbonate rocks during basin weathering.

Analysis on river sediment changes of the upper reaches of Yantze River

The sediment load and river sedimentation of the upper reaches of Yangtze River has been undergoing constant changes as complex landform, large mountain area and plentiful precipitation make the drainage area of Yangtze River very vulnerable to water erosion and gravity erosion. Through analyzing the hydrological and sediment load statistics recorded by major hydrological stations along Yangtze River since 1950s, and editing the accumulation graph of annual runoff volume and annual sediment load, we find out that the suspended-sediment of Yangtze river has been decreasing year by year in Wulong Hydrological Station on Wujiang River. Beibei Hydrological Station on Jialingjiang River, Lijiawan Hydrological Station on Tuojiang River and Gaochang Hydrological Station on Minjiang River, Yichang Hydrological Station, Cuntan Hydrological Station along Yangtze River mainstream share the same experience too. But the statistics obtained at Pingshan Hydrological Station on Jinshajiang River shows the sediment load there has increased. Taking ecological construction, hydraulic engineering construction and precipitation changes into consideration, the thesis analyses the causes for the sediment load decrease of Jialingjiang River, Tuojiang River, Minjiang River and Wujiang River and provides us both scientific foundation for further study of river sediment changes of the upper reaches of Yangtze River, and measures to control river sedimentation.