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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
14 Mar 2017
Review status
A revision of this discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Long term O3-precursor relationships in Hong Kong: Field observation and model simulation
Yu Wang1, Hao Wang1, Hai Guo1, Xiaopu Lyu1, Hairong Cheng2, Zhenhao Ling3, Peter K. K. Louie4, Isobel J. Simpson5, Simone Meinardi5, and Donald R. Blake5 1Air Quality Studies, Department of Civil and Environmental Engineering, Research Institute for Sustainable Urban Development, the Hong Kong Polytechnic University, Hong Kong
2Department of Environmental Engineering, Wuhan University, Wuhan, China
3School of Atmospheric Sciences, Sun Yat-sen University, China
4Air Group, Hong Kong Environmental Protection Department, Hong Kong
5Department of Chemistry, University of California, Irvine, CA, USA
Abstract. Over the past ten years (2005–2014), ground-level O3 in Hong Kong has consistently increased in all seasons except winter, despite the yearly reduction of its precursors, i.e., nitrogen oxides (NOx = O + NO2), total volatile organic compounds (TVOCs) and carbon monoxide (CO). To explain the contradictory phenomenon, an observation-based box model (OBM) coupled with CB05 mechanism was applied in order to understand the influence of both locally-produced O3 and regional transport. The simulation of locally-produced O3 showed an increasing trend in spring, a decreasing trend in autumn and no changes in summer and winter. The O3 increase in spring was caused by the net effect of more rapid decrease of NO titration and unchanged TVOC reactivity despite decreased TVOC mixing ratios, while the decreased local O3 formation in autumn was mainly due to the reduction of aromatic VOC mixing ratios and the TVOC reactivity and much slower decrease of NO titration. However, the decreased in-situ O3 formation in autumn was overridden by the regional contribution, resulting in elevated O3 observations. Furthermore, the OBM-derived relative incremental reactivity indicated that the O3 formation was VOC-limited in all seasons, and the long-term O3 formation was more sensitive to VOCs and less to NOx and CO in the past 10 years. In addition, the OBM results found that the contributions of aromatics to O3 formation decreased in all seasons of these years, particularly in autumn, likely due to effective control of solvent-related sources. In contrast, the contributions of alkenes increased, suggesting a continuing need to reduce traffic emissions. The findings provided updated information on photochemical pollution and its impact in Hong Kong.

Citation: Wang, Y., Wang, H., Guo, H., Lyu, X., Cheng, H., Ling, Z., Louie, P. K. K., Simpson, I. J., Meinardi, S., and Blake, D. R.: Long term O3-precursor relationships in Hong Kong: Field observation and model simulation, Atmos. Chem. Phys. Discuss.,, in review, 2017.
Yu Wang et al.
Yu Wang et al.


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Short summary
Though Hong Kong government has made great efforts on reduction in emissions, ambient O3 levels presented an increasing trend in the past decade. Data analysis and model simulations indicated that the locally-produced O3 in Hong Kong varied by seasons, while regional transport from the PRD region made a substantial contribution to ambient O3 in Hong Kong and even increased in autumn. This long-term study has important implications for other Chinese cities to reduce O3 pollution.
Though Hong Kong government has made great efforts on reduction in emissions, ambient O3 levels...