Heterogenous distribution and burial flux of black carbon in Chinese lakes and its global implication

Black carbon (BC) plays a crucial role in global carbon cycle and climate change. However, its source and burial flux in environments are not well constrained. Here, we investigated surface sediments from 22 Chinese lakes across wide geographical areas and different socioeconomic status. The BC content accounts for 0.09-10.5 % of total organic carbon (TOC), and its average ¹⁴C age is older than that of TOC by 1640 years. The application of δ¹³C-based MixSIAR model shows that the contribution of fossil fuel combustion is highest in the most developed Eastern China (85.7 %) and lowest in the rural Qinghai-Tibetan Plateau (51.4 %), which is corroborated by the results from ¹⁴C-based two endmember mixing model. The BC data from this study and literatures suggest that the current BC burial flux is 126.4 ± 15.8 Gg year^-1 in Chinese lakes, and approximately 2987 ± 1022 Gg year^-1 in global lakes. Globally, lakes accumulate 1.2 %-6.4 % of the total BC production and thus are an important and heterogenous BC sink.