1. Impact assessment of anthropogenic emission control upon aerosol mass burden during heavy pollution episodes over North China Plain Meigen Zhang, Xiao Han LAPC, Institute of Atmospheric Physics Chinese Academy of Sciences, 20 November 2015 17 th GEIA Conference Tsinghua University, Beijing, China

2. Domain & Methodology  94×90 grid cells with a 16 km resolution on a rotated.  Polar stereographic map projection centered at (116°E, 40°N).  15 vertical layers, unequally spaced from the ground to ~23 km, with approximately half of them concentrated in the lowest 2 km to improve the simulation of the atmospheric boundary layer. Brute Force Method Emission sector Zero-out simulations Emission sector Zero-out simulations  Industry  Transport  Power plants  Residential Anthropogenic sources

3. PM 2.5 Mass concentration Monthly average mass concentration of PM 2.5 in NCP An extreme air pollution accompanied by widespread haze cloud appeared in January 2013 over NCP. The monthly average PM 2.5 mass burden could reach 200 μg m -3 in Beijing-Tianjin-Tangshan, and could exceed 250 μg m -3 in southern Hebei province, and part of Shandong and Henan province (Wang et al., 2014; Zhang et al., 2014).

4. Zero-out simulations The PM 2.5 variations upon removal of each emission sector Under the heavy pollution background, the PM2.5 mass burden increased 5-10 μg m -3 by removing the power plants and transport sectors. JanuaryJuly The seasonal variation of residential sectors was significant.

5. Zero-out simulations Variation of major PM 2.5 components upon removal of each emission sector in three regions The major negative value was derived from the nitrate aerosol.

6. Conclusion Nonlinearity & pollution control strategies  The result of the sensitivity tests clearly indicated that the mass burden of secondary aerosol components and emission intensity of precursors did not simply follow a linear relationship under the combined pollution background.  Policy–makers must be aware of the nonlinearity between the emission sources and secondary pollutants. It is suggested that comprehensive pollution control strategies should be implemented based on the specific pollution conditions.  In future work, the nonlinearity of secondary aerosol formation should be further investigated to explore more effective strategies for improving air quality and preventing haze occurrence in the NCP.  The result of the sensitivity tests clearly indicated that the mass burden of secondary aerosol components and emission intensity of precursors did not simply follow a linear relationship under the combined pollution background.  Policy–makers must be aware of the nonlinearity between the emission sources and secondary pollutants. It is suggested that comprehensive pollution control strategies should be implemented based on the specific pollution conditions.  In future work, the nonlinearity of secondary aerosol formation should be further investigated to explore more effective strategies for improving air quality and preventing haze occurrence in the NCP.