Articles | Volume 17, issue 11
Atmos. Chem. Phys., 17, 7127–7142, 2017

Special issue: Regional transport and transformation of air pollution in...

Atmos. Chem. Phys., 17, 7127–7142, 2017

Research article 15 Jun 2017

Research article | 15 Jun 2017

How the OH reactivity affects the ozone production efficiency: case studies in Beijing and Heshan, China

Yudong Yang1, Min Shao1, Stephan Keßel2, Yue Li1, Keding Lu1, Sihua Lu1, Jonathan Williams2, Yuanhang Zhang1, Liming Zeng1, Anke C. Nölscher2,a, Yusheng Wu1,b, Xuemei Wang3, and Junyu Zheng4 Yudong Yang et al.
  • 1State Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Science and Engineering, Peking University, Beijing, China
  • 2Department of Atmospheric Chemistry, Max Plank-Institute for Chemistry, Mainz, Germany
  • 3School of Atmospheric Science, Sun Yat-Sen University, Guangzhou, China
  • 4School of Environmental Science and Engineering, South China University of Technology, Guangzhou, China
  • anow at: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
  • bnow at: Department of Physics, University of Helsinki, Helsinki, Finland

Abstract. Total OH reactivity measurements were conducted on the Peking University campus (Beijing) in August 2013 and in Heshan (Guangdong province) from October to November 2014. The daily median OH reactivity was 20 ± 11 s−1 in Beijing and 31 ± 20 s−1 in Heshan, respectively. The data in Beijing showed a distinct diurnal pattern with the maxima over 27 s−1 in the early morning and minima below 16 s−1 in the afternoon. The diurnal pattern in Heshan was not as evident as in Beijing. Missing reactivity, defined as the difference between measured and calculated OH reactivity, was observed at both sites, with 21 % missing reactivity in Beijing and 32 % missing reactivity in Heshan. Unmeasured primary species, such as branched alkenes, could contribute to missing reactivity in Beijing, especially during morning rush hours. An observation-based model with the RACM2 (Regional Atmospheric Chemical Mechanism version 2) was used to understand the daytime missing reactivity in Beijing by adding unmeasured oxygenated volatile organic compounds and simulated intermediates of the degradation from primary volatile organic compounds (VOCs). However, the model could not find a convincing explanation for the missing reactivity in Heshan, where the ambient air was found to be more aged, and the missing reactivity was presumably attributed to oxidized species, such as unmeasured aldehydes, acids and dicarbonyls. The ozone production efficiency was 21 % higher in Beijing and 30 % higher in Heshan when the model was constrained by the measured reactivity, compared to the calculations with measured and modeled species included, indicating the importance of quantifying the OH reactivity for better understanding ozone chemistry.

Short summary
Total OH reactivity is an important parameter to evaluate understanding of atmospheric chemistry, especially the VOC contribution to air pollution. Measured by comparative reactivity methods, total OH reactivity in Beijing and Heshan revealed significant differences between measured and calculated results, such as missing reactivity, which were related to unmeasured primary or secondary species. This missing reactivity would introduce a 21–30 % underestimation for ozone production efficiency.
Final-revised paper