Evaluation of Anthropogenic Emissions and Ozone Pollution in the North China Plain: Insights from the Air Chemistry Research in Asia (ARIAs) Campaign

Abstract. To study the air pollution in the North China Plain (NCP), the Air Chemistry Research in Asia (ARIAs) campaign conducted airborne measurements of air pollutants including O₃, CO, NO and NO₂ in spring 2016. High concentrations of pollutants, > 100 ppbv of O₃, > 500 ppbv of CO, and > 10 ppbv of NO₂, were observed throughout the boundary layer during the campaign. CMAQ simulations with the 2010 EDGAR emissions can capture the basic spatial and temporal variations of ozone and its major precursors such as CO, NO_x and VOCs, but significantly underestimate their concentrations. Observed emission enhancements of CO and NO_x with respect to CO₂ suggest the existence of combustion with high emissions such as biomass burning in the NCP. The comparison with emission factors from the 2010 EDGAR emission inventory indicates that the contribution of combustion with high emissions has been overestimated. Differences between CMAQ simulations with 2010 emissions and satellite observations in 2016 can reflect the change in anthropogenic emissions. NO_x emissions decreased in megacities such as Beijing and Shanghai confirming the effectiveness of recent control measures in China, while in other cities and rural areas NO_x emissions slightly increased, e.g., CMAQ predicts only ~ 80 % of NO_x observed in the aircraft campaign area. CMAQ also underestimates HCHO (a proxy of VOCs, by ~ 20 %) and CO (by ~ 60 %) over the NCP, suggesting adjustments of the 2010 EDGAR emissions are needed to improve the model performance. HCHO/NO₂ column ratios derived from OMI measurements and CMAQ simulations show that VOC-sensitive chemistry dominates the ozone photochemical production in eastern China, suggesting the importance of tightening regulations on VOCs emissions. We adjusted EDGAR emissions based on satellite observations, conducted sensitivity experiments of CMAQ, and achieved better model performance in simulating ozone, but underestimation still exists. Because of the VOC-sensitive environment in ozone chemistry over the NCP, future study and regulations should focus on VOCs emissions with the continuous controls on NO_x emissions in China.