Anthropogenic-driven chronological increase of sediment organic carbon burial in a river-lake system

Total organic carbon (TOC) in lake sediments from upstream catchments is deposited and buried in substrate, recording historical environmental changes. However, the linkage among natural variability, anthropogenic activity, and TOC burial for has not yet been clarified. This study examined the lake sediments of five 200-cm-deep dated depositional cores in west Dongting lake, China to quantify the magnitude, allocation, and amplitude of TOC burial. 44.47-59.36% of TOC burial flux was buried at 100-200 cm, suggesting lake sediments at deep layers stored considerable carbon. TOC burial rate (BR_TOC) decreased along the lake entrance to its body, which was explained by the geochemical differences. Since 1900, BR_TOC presented an increasing with a 4-7 times uptrend, showing three sedimentary stages with the increased human disturbance, such as deforestation, hydroelectric facilities. Moreover, the coefficient of variation of BR_TOC in the third stage was lower than that in the second stage for the implementation of watershed reforestation and reservoir construction. Our findings stressed that natural variations of lake sedimentation background induced the change of TOC burial among the depositional sites, and enhanced that anthropogenic perturbation drove its chronological increases. This research unveiled the linkage between TOC burial, natural variability, and human disturbance from the perspective of burial evolutions in a lacustrine sedimentary environment.