Spatial and seasonal variations and trends in carbon monoxide over China during 2013–2022

Carbon monoxide (CO) pollution is one of the unsolved atmospheric environmental issues over countries worldwide. Here, we comprehensively assess the spatial-seasonal variations and trends in CO over China during 2013–2022, by site categorization and cause analysis, which have not been reported in previous studies. Our analysis is based on surface observations, statistical classification techniques, and sensitivity simulations from a global chemical transport model, GEOS-Chem. The results show that CO concentrations and their seasonal variation are higher over the North China Plain than other areas of China during 2013–2022. CO concentrations have decreased at −38.2±31.4 ppbv yr −1 (−3.7%±1.8% yr −1 ) over China during 2013–2022. The declining trends in CO concentrations vary with space, stronger over larger, more polluted, and more industralized cities. GEOS-Chem simulations suggest that the decrease in CO anthropgenic emissions in China would be the main driver for the decreasing trends of CO over China, with a contribution of 80% to the trend. Meteorology, CO anthropgenic emissions over foreign regions, and emissions from biomass burning are the remaining drivers. Our results suggest remarkable benefits of emission reductions in China in abating CO pollution and enhance our understanding on trends of long-term CO pollution over China during 2013–2022. • CO concentrations and their seasonal variation are higher over the North China Plain than other areas of China during 2013–2022. • CO concentrations decreased at −38.2±31.4 ppbv yr −1 (−3.7%±1.8% yr −1 ) over China during 2013–2022 and the declining trends are stronger over larger, more polluted, and more industralized cities. • CO anthropogenic emissions over China are the major driver for the CO declining trends over China during 2013–2022, and meteorology, CO anthropogenic emissions over foreign regions, and emissions from biomass burning dominate the left.