Comparisons of sediment mass accumulation rates in different regions of Dongting Lake and their environmental indications: Based on 239+240Pu, 137Cs, and 210Pbex

Abstract

In this study, 24 sediment cores collected from Dongting Lake were detected by inductively coupled plasma-mass spectrometry and HPGe γ-spectrometer for ^239+240Pu, ¹³⁷Cs, ²²⁶Ra, and ²¹⁰Pb, respectively. Based on the vertical profiles of ²¹⁰Pb_ex, ^239+240Pu, and ¹³⁷Cs, sediment mass accumulation rates (MAR) were calculated, and the responses to major environmental events and anthropogenic activities were discussed. The vertical profiles of ¹³⁷Cs and ^239+240Pu exhibit bimodal distribution, the secondary peaks most probably indicated the fallout from a series of Chinese nuclear tests (CNT) during the 1970s. Comparisons of the Constant Initial Concentration (CIC) model, the Constant Flux Constant Sedimentation (CFCS) model, and the Constant Rate of Supply (CRS) model reveal that some sites in Dongting Lake are unsuitable for ²¹⁰Pb_ex dating. The MARs derived from different methods show the spatial distribution characteristics in the order of West Dongting Lake (WDL) > South Dongting Lake (SDL) > East Dongting Lake (EDL). Comparisons of the three methods confirm that the ²¹⁰Pb_ex method is a valuable tool for evaluating the impact of environmental changes and human activities in different periods. In this study, the MARs derived from the ²¹⁰Pb_ex method show significant correlations with hydrological data and accurately reflect key environmental change events in Dongting Lake, including the widespread drought in 2011, the operation of the Three Gorges Dam in 2006, the major flood in 1998, and localized flooding events in the Yuan River and Xiangjiang River.