Characteristics and Sources of Dissolved Inorganic Carbon in the Chongqing Urban Area of the Three Gorges Reservoir Region

Understanding the dynamic characteristics of carbon cycling in reservoir ecosystems during floods is of great significance for comprehensively understanding global carbon cycling. Dissolved inorganic carbon (DIC) is an important component of the carbon pool in water bodies and the main body of carbon cycling in reservoirs. In this study, the Chongqing main urban section of the Yangtze River basin was selected as the research area. Low-water and reservoir periods were chosen, and the proportion and content of DIC in the reservoir water, as well as δ13C-DIC, were measured. Carbon stable isotope technology and a mass balance model were used to analyze the main sources of DIC and their influencing factors. The results showed that: DIC is the main source of carbon in the Yangtze River main section; there are two main sources of DIC, namely, DIC in the form of soil CO2 and DIC in the form of bicarbonate produced by the weathering of carbonate minerals; thermal stratification of the water column has a significant effect on the carbon cycle of water; and DIC and other processes show a stacking effect; In summer, δ13C-DIC shows a significant negative correlation with temperature T and p(CO2) (P<0.001), and a significant positive correlation with pH and TPM (P<0.05); DIC content and δ13C-DIC showed a highly significant negative correlation in autumn.