资源环境科技发展态势分析平台

Large emission reductions of anthropogenic nitrogen oxides (NO_x) due to the coronavirus disease 2019 (COVID-19) lockdown policies in China have been extensively reported since the outbreak, while assessments of sectoral emission changes during that period are still limited. In this study, a source-oriented community multiscale air quality (CMAQ) model was applied to quantify NO₂ concentrations from major emission sectors. A new optimization approach was employed to obtain the sectorial emission reductions using satellite and ground-level observations as constraints. The optimized emissions significantly improved the model performance of NO₂ during the lockdown period. February NO_x emission changes varied with regions and sectors, with relatively larger reductions in transportation (286.6 kt) and industrial sources (260.1 kt). The maximum amount of NO_x emission reduction occurred in the North China Plain (230.6 kt). Our work presents a quick and reliable technique for assessing sector-specific emission changes due to short-term emission control policies.