Distribution, sources, and burial flux of black carbon in sediment of Daye lake, central China

Black carbon (BC), primarily originating from fossil fuel and biomass combustion, holds significance for global carbon cycling, climate change, and human health. Despite a lake's role as a carbon sink, detailed information about BC sedimentary burial flux and sink in its sediment remains insufficiently explored. The current study investigates the distribution, sources, and burial flux of BC and its subtypes (char and soot) in the surface sediment of Daye Lake, the largest lake in Huangshi City, central China. BC concentrations in the sediment ranged from 0.10 to 3.60 mg/g, corresponding to 0.40%–17.02% of organic carbon (OC). Higher values of BC and BC/OC observed in the western region suggest direct terrestrial input via river discharge and surface runoff, influenced by anthropogenic activities. In contrast, variations in char/soot ratios reflect diverse combustion sources and hydrological dynamics in different regions. The indications from BC/OC and char/soot ratios imply that fossil fuel combustion is the predominant sources. The weak correlations between BC and OC suggest that they may come from different sources or undergo different processes that affect their distribution in the lake sediment. However, a stronger correlation was observed between BC and soot, as well as between char and soot, indicating potential similarities in their input pathways. The BC burial flux displays notable variations across the lake, ranging from 0.69 to 24.07 g/m²/yr, with elevated values observed in the western region. The BC sink in the sediments of Daye Lake was estimated to be 0.635 Gg/yr. Though locally small, it significantly contributes to the broader picture of BC burial in Chinese lakes and the global distribution of BC in lake ecosystems.