How does the OH reactivity affect the ozone production efficiency: case studies in Beijing and Heshan
19 Total OH reactivity measurements have been conducted in August 2013 on the 20 Peking University campus, Beijing and from October to November 2014 in Heshan, 21 Guangdong Province. The daily median result for OH reactivity was 19.98 11.03 s 22 in Beijing and 30.62 19.76 s in Heshan. Beijing presented a significant diurnal 23 variation with maxima over 27 s in the early morning and minima below 16 s in the 24 afternoon. Measurements in Heshan gave a much flatter diurnal pattern. Missing 25 reactivity was observed at both sites, with 21% missing in Beijing and 32% missing in 26 Heshan. Unmeasured primary species, such as branched alkenes could contribute to 27 missing reactivity in Beijing, especially in morning rush hour. An observation based 28 model with the Regional Atmospheric Chemical Mechanism 2 was used to understand 29 the daytime missing reactivity in Beijing by adding unmeasured oxygenated volatile 30 organic compounds and simulated intermediates of primary VOCs degradation. 31 However, the model failed to explain the missing reactivity in Heshan, where the 32 ambient air was found to be more aged, and the missing reactivity was presumably to 33 Atmos. Chem. Phys. Discuss. doi:10.5194/acp 2016 507, 2016 Manuscript under review for journal Atmos. Chem. Phys. Published: 15 July 2016 c (c) Author(s) 2016. CC BY 3.0 License.