Spatio-temporal variations of ¹³⁷Cs in lacustrine sediment of China and its implication for Anthropocene

Due to differences in natural environments and levels of socio-economic development across different regions, finding evidence of when human activities began to have a significant and synchronous impact on the earth system has become a key issue in Anthropocene research. As an artificial radionuclide, 137Cs is considered as a suitable stratigraphic marker of the Anthropocene because it is widely distributed around the world, closely related to human activities, clearly marked and easily recognized in sediments. The 137Cs accumulation peaks of 137Cs formed by human activities such as nuclear tests and nuclear accidents, as an important chronological marker, has been widely used for dating lacustrine sediments. Therefore, exploring the regional spatial distribution characteristics and patterns of 137Cs can provide significant evidence for a deeper understanding of the temporal characteristics of the Anthropocene and global synchronous signals. This study collected and compiled 137Cs data from 79 lakes and wetland sediment cores within China, examining their the spatio-temporal distribution characteristics and and exploreing the starting boundary of the Anthropocene. The results show that: 1) The 137Cs sedimentary records in lacustrine drill coresalmost detect the accumulation peak of 1963 in China, indicating that the main chronological marker layer of 1963 is clearly distinguishable and easily recognizable. With distinct chronological characteristics, the 137Cs accumulation peak of 1986 in the sedimentary drill cores can be used as a secondary chronological marker, but its reliability needs to be confirmed in combination with other dating indicators. 2) The records of 137Cs exhibit significant spatio-temporal differentiation across China, which influenced by multiple factors, including topography, precipitation, environmental factors, erosion by runoff, and various human activities. Overall, the specific activity of 137Cs shows a decreasing trend from north to south, and the specific activity values of 137Cs reached the highest level in the lacustrine sedimentary of the Chinese region during the period of 1960 to 1980. 3) The main 137Cs accumulation peak of 1963 in lacustrine drill cores has clear chronological characteristics and is a reliable chronological layer marker in China, which can be used as a potential stratigraphic evidence to indicate the impact of human activities on regional environments.