Observation of atmospheric CO2 and CO in a low-carbon pilot city: insight into CO2 sources and regional transport

The first batch of eight low-carbon pilot cities in China includes Tianjin, Hangzhou and Nanchang etc., in which Nanchang is the only one located in center China. In this study, two-year in-situ measurements of atmospheric CO2 and CO were conducted at Nanchang station. The yearly averages of CO2 and CO mole fraction were 426.2 ppm and 449.2 ppb in 2019, 430.8 ppm and 384.4 ppb in 2020, respectively. We confirmed the significant influence of local sources on distributing the profile of CO2 and CO based on the serial analysis of their diurnal and seasonal pattern and the impacts of surface wind. The enhancements of CO2 (Delta CO2) and CO (Delta CO) in polluted conditions relative to the regionally representative conditions showed significant positive correlation in winter, with the average CO2/CO emission ratio of 54.1 ppm/ppm, suggesting their common-source from anthropogenic emissions. Specifically, we found the yearly averaged anthropogenic CO2 enhancement decreased from 7.07 ppm in 2019 to 6.72 ppm in 2020, probably due to higher fossil fuel combustion efficiency and more use of clean energy in center China. In addition, results from cluster analysis, weighted potential source contribution function, and the contribution ratio calculation demonstrated that the significant sources mainly distributed in the central and eastern Hubei in spring, Jiangxi, Guangdong and Fujian province in summer, eastern Hubei, southern Henan, central and western Shandong, northern Anhui and Jiangxi in autumn, and southern Henan, eastern Hubei, eastern and northern of Hunan, central and southern Jiangxi, northern Anhui and Jiangsu in winter.