210PB, 137CS AND 7BE AS TRACERS FOR SEDIMENT DEPOSITION IN AN EMBAYMENT OF THREE GORGES RESERVOIR, CHINA

The Xiangxi Bay in the lower reach of the Xiangxi River, a tributary of the Yangtze River, is an embayment of the Three Gorges Reservoir. To understand environmental impact on sedimentation due to human activities, a sediment core (~3 m long) was retrieved from the Xiangxi Bay on May 6, 2018, for analysis of natural and anthropogenic radionuclides (210Pb, 137Cs and 7Be) that can be used as tracers for sedimentation in the area. The results show that 7Be activity is undetectable, suggesting that there is no natural sediment deposition in the study area in the recent period (<8 months), and 210Pb profile suggests that long-term steady-state sedimentation is absent in this area. The minimum excess 210Pb inventory in the sediments in the study area is ~8 times higher than the normal atmospheric supply, which suggests a huge amount of sediment deposition in the study area. The 137Cs profile suggests that these sediments deposited in the study area could be from 3 – 4 different sources and have a similar “age.” Therefore, the results suggest that the recent land-use change and human activities may have made a significant impact on the local environment.