Rapid decline of carbon monoxide emissions in the Fenwei Plain in China during the Three-year Action Plan on Defending the Blue Sky

The Fenwei Plain is one of China’s most polluted regions, with poor atmospheric dispersion conditions and an outdated energy structure. After implementing multiple policies in recent years, significant reductions in air pollutant concentrations were observed. We inferred high-resolution carbon monoxide (CO) emissions of the Fenwei Plain by inversion of observed atmospheric concentrations and analyzed the causes for variations in CO emissions, especially the effect of the “Three-year Action Plan on Defending the Blue Sky” (TAPDBS). Before the policy went into action, CO emissions temporarily increased and the overall decrease in CO emissions per unit of Gross Domestic Product (GDP) slowed down. When the policy was implemented, CO emission fluxes declined sharply, with an average drop of 28%, accompanied by an even higher 37% decrease of the CO emission per GDP. Thus, the TAPDBS has brought a breakthrough in both economic development and air quality protection in the Fenwei Plain.