Articles | Volume 14, issue 23
Atmos. Chem. Phys., 14, 13175–13188, 2014

Special issue: Atmospheric impacts of Eastern Asia megacities

Atmos. Chem. Phys., 14, 13175–13188, 2014

Research article 10 Dec 2014

Research article | 10 Dec 2014

Ground-level ozone in four Chinese cities: precursors, regional transport and heterogeneous processes

L. K. Xue1,2, T. Wang1,2,3, J. Gao3, A. J. Ding4, X. H. Zhou2, D. R. Blake5, X. F. Wang2, S. M. Saunders6, S. J. Fan7, H. C. Zuo8, Q. Z. Zhang2, and W. X. Wang2,3 L. K. Xue et al.
  • 1Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hong Kong, China
  • 2Environment Research Institute, Shandong University, Ji'nan, Shandong, China
  • 3Chinese Research Academy of Environmental Sciences, Beijing, China
  • 4Institute for Climate and Global Change Research and School of Atmospheric Sciences, Nanjing University, Nanjing, Jiangsu, China
  • 5Department of Chemistry, University of California at Irvine, Irvine, CA, USA
  • 6School of Chemistry and Biochemistry, University of Western Australia, Crawley, Perth WA, Australia
  • 7College of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, Guangdong, China
  • 8College of Atmospheric Sciences, Lanzhou University, Lanzhou, Gansu, China

Abstract. We analyzed the measurements of ozone (O3) and its precursors made at rural/suburban sites downwind of four large Chinese cities – Beijing, Shanghai, Guangzhou and Lanzhou, to elucidate their pollution characteristics, regional transport, in situ production, and impacts of heterogeneous processes. The same measurement techniques and observation-based model were used to minimize uncertainties in comparison of the results due to difference in methodologies. All four cities suffered from serious O3 pollution but showed different precursor distributions. The model-calculated in situ O3 production rates were compared with the observed change rates to infer the relative contributions of on-site photochemistry and transport. At the rural site downwind of Beijing, export of the well-processed urban plumes contributed to the extremely high O3 levels (up to an hourly value of 286 ppbv), while the O3 pollution observed at suburban sites of Shanghai, Guangzhou and Lanzhou was dominated by intense in situ production. The O3 production was in a volatile organic compound (VOC)-limited regime in both Shanghai and Guangzhou, and a NOx-limited regime in Lanzhou. The key VOC precursors are aromatics and alkenes in Shanghai, and aromatics in Guangzhou. The potential impacts on O3 production of several heterogeneous processes, namely, hydrolysis of dinitrogen pentoxide (N2O5), uptake of hydro peroxy radical (HO2) on particles and surface reactions of NO2 forming nitrous acid (HONO), were assessed. The analyses indicate the varying and considerable impacts of these processes in different areas of China depending on the atmospheric abundances of aerosol and NOx, and suggest the urgent need to better understand these processes and represent them in photochemical models.

Final-revised paper