Sedimentological\nCharacteristics of <sup>239+240</sup>Pu and <sup>137</sup>Cs in the\nSedimentary Deposits of Poyang Lake

The spatial and vertical distribution of <sup>239+240</sup>Pu and <sup>137</sup>Cs in sediments of Poyang Lake was studied to\nassess the\ndynamics of disposition and the pollution status. The activities of <sup>239+240</sup>Pu and <sup>137</sup>Cs in surface sediments ranged\nfrom 0.005 to 0.616 Bq/kg and from 0.70 to 5.82 Bq/kg, respectively.\nThe inventories of <sup>239+240</sup>Pu in sediment cores of PYA and\nPYB were determined to be 75.2 and 19.9 Bq/m<sup>2</sup>, respectively.\nIn sediment core PYA, the activity of <sup>239+240</sup>Pu ranged\nfrom 0.043 to 0.485 Bq/kg, while that for <sup>137</sup>Cs ranged\nfrom 0.39 to 6.80 Bq/kg. An accumulation peak along with two secondary\npeaks was observed in sediment core PYA, suggesting a correlation\nbetween the timing of these subpeaks and flood events in Poyang Lake.\nBy employing <sup>239+240</sup>Pu, the average deposition rate for\ncore PYA was calculated as 0.79 cm/year from 1954 to 1998 and as 0.44\ncm/year from 1998 to 2022. The results also suggested that the deposition\nrate of Poyang Lake has been impacted by human activities, such as\nthe construction of water conservancy projects around Poyang Lake\nand the commissioning of the Three Gorges Dam Project.