Impact on the Daning river sedimental environment by Three Gorge Reservoir in view of changes in sediment compositions

This study shows the results of analysis to X-ray diffraction （XRD）, total carbon （TC） and the total organic carbon （TOC） contents of fluvial sediment core nearly 42cm long collected from the Daning river. Three primary results are concluded： （1） The XRD results indicate that quartz and calcite are the dominant minerals in the sediment. The TC and TOC contents range from 33 to 57g/kg and from 8 to 34g/kg, respectively. （2） From 10cm deep toward the core top both TC and TOC continuously decrease and the sediment become brown color. The Three Gorge Reservoir may elevate water level and leads to dramatic increase in input of brownish low carbon content clay sediment into the Daning river. Then the sediment rate of the Daning river will be increased dramatically by this mechanism. （3） From 10 to 17 cm deep in Shuanglong profile, TOC content in the sediment dramatic increase may be resulted from intensive human activities which lead more organic matter input into the Daning river..[