Source appointment of δ13C in sediments of a maar lake in southern China: Implications of fossil fuel CO2 emissions

Abstract

Stable carbon isotopes (δ13C) in lake sediments can record changes in CO2 emissions from fossil fuels (FFs) combustion; however, the exact proportion of δ13C changes caused by FFs combustion remains unclear. Here, taking the Huguangyan Maar Lake (HGY) located in low latitude with high intensity of human activities in southern China as an example, we used the MixSIAR Bayesian stable isotope mixing model to trace the source change of δ13C in the HGY sediments over the past 130 years. The δ13C value, ranging from −20.23‰ to −24.29‰, with an average of −22.39 ± 1.5‰, displayed a continuous downward trend from the bottom to top throughout the core, with the fastest decline occurring between 1950AD and 1996AD. Quantitative source appointment indicates that the contribution of FFs sources to δ13C depletion in the HGY sediments has increased nearly three-fold over the past 130 years, from 18.6% to 67.8%, which may be related to the Suess Effect of the 13C-depleted FFs burning. The increase in δ13C in HGY sediments in the past decade was consistent with the increase in δ13C–CO2 emitted by global fossil-fuel consumption, and was also related to the decrease in fossil fuels consumption caused by China's Clean Air Act. This study demonstrates that the isotope traceability model is helpful for source appointment of δ13C in lake sediments and that the δ13C in maar lake sediments can be used to trace CO2 emissions from global FFs combustion. This therefore provides new insights on the carbon cycle during the Anthropocene.