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Title: Atmospheric photochemical reactivity and ozone production at two sites in Hong Kong : application of a Master Chemical Mechanism - photochemical box model
Authors: Ling, ZH
Guo, H 
Lam, SHM
Saunders, SM
Wang, T 
Issue Date: 2014
Publisher: Wiley-Blackwell
Source: Journal of geophysical research. Atmospheres, 2014, v. 119, no. 17 How to cite?
Journal: Journal of geophysical research. Atmospheres 
Abstract: A photochemical box model incorporating the Master Chemical Mechanism (v3.2), constrained with a full suite of measurements, was developed to investigate the photochemical reactivity of volatile organic compounds at a semirural site (Mount Tai Mo Shan (TMS)) and an urban site (Tsuen Wan (TW)) in Hong Kong. The levels of ozone (O-3) and its precursors, and the magnitudes of the reactivity of O-3 precursors, revealed significant differences in the photochemistry at the two sites. Simulated peak hydroperoxyl radical (HO2) mixing ratios were similar at TW and TMS (p = 0.05), while the simulated hydroxyl radical (OH) mixing ratios were much higher at TW (p < 0.05), suggesting different cycling processes between OH and HO2 at the two sites. The higher OH at TW was due to high-NO mixing ratios, which shifted the HOx (OH + HO2) balance toward OH by the propagation of HO2 and alkyl peroxy radicals (RO2) with NO. HOx production was dominated by O-3 photolysis at TMS, but at TW, both HCHO and O-3 photolyses were found to be major contributors. By contrast, radical-radical reactions governed HOx radical losses at TMS, while at TW, the OH + NO2 reaction was found to dominate in the morning and the radical-radical reactions at noon. Overall, the conversion of NO to NO2 by HO2 dictated the O-3 production at the two sites, while O-3 destruction was dominated by the OH + NO2 reaction at TW, and at TMS, O-3 photolysis and the O-3+HO2 reaction were the major mechanisms. The longer OH chain length at TMS indicated that more O-3 was produced for each radical that was generated at this site.
ISSN: 2169-897X
EISSN: 2169-8996
DOI: 10.1002/2014JD021794
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