Optimal emission reduction scheme aimed at eliminating PM2.5 city pollution days within North China during a haze episode

Economic development is accompanied by pollutant emissions, and environmental management plans should be urgently formulated to maximize air quality improvement under the premise of minimizing total amount of precursor emissions. The purpose of this study was to establish an optimal emission reduction system through a linear programming method based on source analysis, fine particulate matter (PM2.5) sensitivity, emission status, and pollution conditions to readjust the industrial layout within China and to achieve the goal of eliminating PM2.5 city pollution days (PMCPDs) during a PM2.5 pollution episode in North China. The WRF-NAQPMS simulations showed that the total PM2.5 sensitivity (the impact of unit precursor emission on air quality) increased with increasing precursor emission perturbation, and the order of each precursor was primary PM2.5 > NOx > SO2 > NH3 > volatile organic compounds (VOCs) in most receptors. Compared to the equal proportion (EP) scenario, not only were the emission reduction ratios of primary PM2.5, SO2, NOx, NH3, and VOCs in North China approximately 7.27%, 9.78%, 10.27%, 5.09%, and 26.34% lower, respectively, but the air quality improvement was also greater under the optimal proportion (OP) scenario. North China could achieve the goal of eliminating PMCPDs under the OP scenario, while the number increased by thirteen in Northwest China. Through technological upgrading in industrial transfer from North China to Northwest China (OPTU scenario), the number of PMCPDs in North China could not only be eliminated but a zero-increase relative to the business as usual (BAU) scenario could also be achieved in Northwest China.