Abstract:

This study explored the burial characteristics and sources of organic carbon in sediments of Tian-e-zhou oxbow lake in the middle reaches of Yangtze river. The sediment accumulation rate (SAR), organic carbon accumulation rate (OCAR) and the temporal and spatial variations of organic carbon sources were analyzed, based on the characteristics of the 210 Pbex dating technique. Particle size analysis, stable isotopes of carbon (δ13C and δ15N) and carbon to nitrogen ratio (C/N) were also adopted in the dating method. The results showed that, the SAR range of the column was 0.60~0.78 cm·a-1, and the average OCAR was 92.2 g·m-2·a-1. This value fluctuated significantly from 1950s to 1990s due to the disturbance of flood events and human activities. It became relatively stable after 1990s. The δ13C and C/N analysis showed that the organic carbon was mainly derived from exogenous inputs (58.76%), in which C3 plants were the main sources, and the endogenous contribution was small. OCAR was significantly positively correlated with exogenous total organic carbon (TOC) and total nitrogen (TN), which indicated that exogenous input was a key driving factor of organic carbon burial. The study revealed the regulatory effect of the sedimentary environment on organic carbon burial, and provided a scientific basis for carbon cycle assessment and management of regional wetlands.