Tracing CO2 emission characteristics in Central China based on the simultaneous measurements of atmospheric CO2, CO and δ13C.

Although atmospheric CO2 observations are becoming increasingly widespread in China, the identification of CO2 emission sources is still scarce, especially in undeveloped Central China. To effectively address this issue, in a typical site in Central China, the simultaneous measurements of atmospheric CO2, CO, and δ13C were conducted, and the characteristics of CO2 emission sources were systematically investigated based on the relationships among CO2, CO, and δ13C. The average CO2/CO ratio of winter increased from 52.4 ppm/ppm during 2018-2020 to 65.1 ppm/ppm during 2021-2022, which confirmed the improvement of energy consumption efficiency in China. Air-mass transportation from central China and Yangtze River Delta regions contributed largely to higher CO2/CO ratios in 2021-2022. A higher mean CO2/CO ratio appeared during the morning rush hours (60.3 ppm/ppm) than in the afternoon rush hours (51.4 ppm/ppm) in winter. In addition, the mean δ13C value of CO2 sources (δ13Cs) also displayed more negative values during the morning rush hours (-28.3 ‰) than the afternoon rush hours (-22.2 ‰), suggesting the significant influence of vehicle and natural gas usage at the morning rush hours and the impact of straw burning in the afternoon rush hours. The mean δ13Cs was -24.7 ‰ for winter and -21.9 ‰ for vegetation season, implying the main contribution of coal in winter and the impact of C4 plants during the vegetation season. The contribution of biogenic respiration CO2 was inferred to exceed 50 % during the nighttime of summer according to the obtained mean δ13C value of biogenic respiration CO2, which was calculated to be -21.4 ‰.