Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 8, 3151-3162, 2015
https://doi.org/10.5194/gmd-8-3151-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Development and technical paper
07 Oct 2015
Development of a chlorine chemistry module for the Master Chemical Mechanism
L. K. Xue1, S. M. Saunders2, T. Wang1,3, R. Gao1, X. F. Wang1, Q. Z. Zhang1, and W. X. Wang1 1Environment Research Institute, Shandong University, Ji'nan, Shandong, China
2School of Chemistry and Biochemistry, University of Western Australia, WA, Australia
3Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hong Kong, China
Abstract. The chlorine atom (Cl·) has a high potential to perturb atmospheric photochemistry by oxidizing volatile organic compounds (VOCs), but the exact role it plays in the polluted troposphere remains unclear. The Master Chemical Mechanism (MCM) is a near-explicit mechanism that has been widely applied in the atmospheric chemistry research. While it addresses comprehensively the chemistry initiated by the OH, O3 and NO3 radicals, its representation of the Cl· chemistry is incomplete as it only considers the reactions for alkanes. In this paper, we develop a more comprehensive Cl· chemistry module that can be directly incorporated within the MCM framework. A suite of 205 chemical reactions describes the Cl·-initiated degradation of alkenes, aromatics, alkynes, aldehydes, ketones, alcohols, and some organic acids and nitrates, along with the inorganic chemistry involving Cl· and its precursors. To demonstrate the potential influence of the new chemistry module, it was incorporated into a MCM box model to evaluate the impacts of nitryl chloride (ClNO2), a product of nocturnal halogen activation by nitrogen oxides (NOX), on the following day's atmospheric photochemistry. With constraints of recent observations collected at a coastal site in Hong Kong, southern China, the modeling analyses suggest that the Cl· produced from ClNO2 photolysis may substantially enhance the atmospheric oxidative capacity, VOC oxidation and O3 formation, particularly in the early morning period. The results demonstrate the critical need for photochemical models to include more detailed chlorine chemistry in order to better understand the atmospheric photochemistry in polluted environments subject to intense emissions of NOX, VOCs and chlorine-containing constituents.

Citation: Xue, L. K., Saunders, S. M., Wang, T., Gao, R., Wang, X. F., Zhang, Q. Z., and Wang, W. X.: Development of a chlorine chemistry module for the Master Chemical Mechanism, Geosci. Model Dev., 8, 3151-3162, https://doi.org/10.5194/gmd-8-3151-2015, 2015.
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Short summary
A detailed chemical mechanism including 205 reactions is developed for use in the Master Chemical Mechanism. With this new chlorine mechanism, it was found that the nocturnal formation of ClNO2 has high potential to perturb the next day's atmospheric photochemistry, by enhancing the radical production and cycling, VOC oxidation and O3 formation, in the polluted coastal environments.
A detailed chemical mechanism including 205 reactions is developed for use in the Master...
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