The records of Pu and Cs of global fallout in Lake East Dongting Sediments and Responses to watershed environmental changes.

Plutonium-239 + 240 and Cs in the environment can usually be used to track the impact of nuclear activities on the environment, and have become important tools in environmental geochemical studies. In this study, nine sediment cores (E1-E9) in Lake East Dongting were collected and measured for the activity concentration of Pu, Cs and the atomic ratio of Pu/Pu, and then their vertical distribution characteristics were analyzed. The results show that: the activity concentrations of Cs and Pu in Lake East Dongting ranged from 5.26 ± 0.43 to 28.6 ± 2.23 Bq kg and 0.29 ± 0.02 to 1.37 ± 0.09 Bq kg, with an average of 7.48 ± 0.68 Bq kg and 0.39 ± 0.03 Bq kg, respectively. The atomic ratios of Pu/Pu are 0.168 ± 0.012-0.211 ± 0.015, which are basically consistent with the global atmospheric deposition. The vertical profiles of Cs and Pu in sediment cores show obvious single-peak distribution in E1-E6 and bimodal distribution in E7-E9. The results of sedimentation rates calculated by Cs and Pu method ranged from 0.59 cm y to 1.99 cm y with a mean of 1.18 cm y and 0.61 cm y to 2.18 cm y with a mean of 1.26 cm y. The inventories of Cs and Pu in nine sediment cores are 5.87-10.8 kBq m and 307-545 Bq m, which are about 8-14 and 9-15 times the inventory in the global average atmospheric deposition at the same latitude respectively. Comparing the results of the sedimentation rates and the inventories from different sampling points indicates that extreme climatic events and human activities have a significant impact on sediment environment of Lake East Dongting.