Oxidative capacity and radical chemistry in the polluted atmosphere of Hong Kong and Pearl River Delta region: analysis of a severe photochemical smog episode
Item
Title (Dublin Core)
Oxidative capacity and radical chemistry in the polluted atmosphere of Hong
Kong and Pearl River Delta region: analysis of a severe photochemical smog
episode
Kong and Pearl River Delta region: analysis of a severe photochemical smog
episode
Description (Dublin Core)
We analyze a photochemical smog episode to understand the oxidative capacity and radical chemistry of the polluted atmosphere in Hong Kong and the Pearl River Delta (PRD) region. A photochemical box model based on the Master Chemical Mechanism (MCM v3.2) is constrained by an intensive set of field observations to elucidate the budgets of RO<sub><i>x</i></sub> (RO<sub><i>x</i></sub> = OH+HO<sub>2</sub>+RO<sub>2</sub>) and NO<sub>3</sub> radicals. Highly abundant radical precursors (i.e. O<sub>3</sub>, HONO and carbonyls), nitrogen oxides (NO<sub><i>x</i></sub>) and volatile organic compounds (VOCs) facilitate strong production and efficient recycling of RO<sub><i>x</i></sub> radicals. The OH reactivity is dominated by oxygenated VOCs (OVOCs), followed by aromatics, alkenes and alkanes. Photolysis of OVOCs (except for formaldehyde) is the dominant primary source of RO<sub><i>x</i></sub> with average daytime contributions of 34–47 %. HONO photolysis is the largest contributor to OH and the second-most significant source (19–22 %) of RO<sub><i>x</i></sub>. Other considerable RO<sub><i>x</i></sub> sources include O<sub>3</sub> photolysis (11–20 %), formaldehyde photolysis (10–16 %), and ozonolysis reactions of unsaturated VOCs (3.9–6.2 %). In one case when solar irradiation was attenuated, possibly by the high aerosol loadings, NO<sub>3</sub> became an important oxidant and the NO<sub>3</sub>-initiated VOC oxidation presented another significant RO<sub><i>x</i></sub> source (6.2 %) even during daytime. This study suggests the possible impacts of daytime NO<sub>3</sub> chemistry in the polluted atmospheres under conditions with the co-existence of abundant O<sub>3</sub>, NO<sub>2</sub>, VOCs and aerosols, and also provides new insights into the radical chemistry that essentially drives the formation of photochemical smog in the high-NO<sub><i>x</i></sub> environment of Hong Kong and the PRD region.
Creator (Dublin Core)
Xue, Likun
Gu, Rongrong
Wang, Tao
Wang, Xinfeng
Saunders, Sandra
Blake, Donald
Louie, Peter K. K.
Luk, Connie W. Y.
Simpson, Isobel
Xu, Zheng
Wang, Zhe
Gao, Yuan
Lee, Shuncheng
Mellouki, Abdelwahid
Wang, Wenxing
Date (Dublin Core)
2018-09-13
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-16-9891-2016
https://acp.copernicus.org/articles/16/9891/2016/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
