Carbon burial characteristics of Hongze Lake in the past 60 years

Abstract

Lakes are important carbon sinks in terrestrial ecosystems. Currently, most of lake carbon burial research in China only considers organic carbon burial and has neglected inorganic carbon burial, which will lead to an underestimation of the total carbon burial capacity of lakes. This situation is particularly significant in the humid eastern plain region. In order to comprehensively understand the carbon burial characteristics of lakes in the eastern plain and evaluate the contributions of organic and inorganic carbon burial to total carbon burial more reasonably. This research chooses Hongze Lake as study site, which is a representative lake in the eastern plain region. Based on the 210Pb-137Cs chronological sequence, combined with the C/N and δ13C characteristics in sediments, the carbon burial characteristics of Hongze Lake sediments in the past 60 years were explored by analyzing the spatiotemporal changes of organic and inorganic carbon content in typical rock cores (numbered HZH-12) and 11 other surface sediments. C/N and δ13C shows that endogenous organic carbon is the main source of organic carbon inHongze Lake . The significant synergistic changes in the accumulation rates of organic and inorganic carbon over the past 60 years (R2=0.76, p<0.001) indicate that inorganic carbon may be derived from secondary carbonate deposition caused by the photosynthesis of planktonic algae. Results show that the inorganic carbon content (1.09%) is significantly higher than organic carbon content (0.61%). The accumulation rate of inorganic carbon is 34.27 g/(m2·a), which is significantly higher than that of organic carbon with a value of 25.27 g/(m2·a), too. In general, organic carbon accounts for 42.4% of total carbon burial, while inorganic carbon accounts for up to 57.6% of total carbon burial. This means that ignoring the burial of inorganic carbon may lead to a significant underestimation of the carbon burial capacity of lakes in the eastern plain. And for the lake carbon burial study in this region, it is necessary to consider both organic and inorganic carbon burial in the future.

Keywords

• carbon burial
• organic carbon
• inorganic carbon
• hongze lake