EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Significant production of ClNO2 and possible source of Cl2 from N2O5 uptake at a suburban site in eastern China

Men Xia1, Tao Wang1, Xiang Peng1, Weihao Wang1, Chuan Yu1, Peng Sun2, Yuanyuan Li2, Yuliang Liu2, Zhengning Xu2, Zhe Wang3, Zheng Xu2, Wei Nie2, and Aijun Ding2
Men Xia et al.
  • 1Department of civil and environmental engineering, The Hong Kong Polytechnic University, Hong Kong, China (;
  • 2Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing, China
  • 3Division of Environment and Sustainability, Hong Kong University of Science and Technology, Hong Kong, China

ClNO2 and Cl2 can affect atmospheric oxidation and thereby the formation of ozone and secondary aerosols, yet their sources and production mechanisms are not well understood or quantified. In this study we present field observations of ClNO2 and Cl2 at a suburban site in eastern China during April 2018. Persistent high levels of ClNO2 (maximum ~3.7 ppbv; 1 min average) were frequently observed at night, due to the high ClNO2 yield (φ(ClNO2), 0.56 ± 0.20) inferred from the measurements. The φ(ClNO2) value showed a positive correlation with the [Cl-]/[H2O] ratio, and its parameterization was improved by the incorporation of [Cl-]/[H2O] and the suppression effect of aerosol organics. ClNO2 and Cl2 showed a significant correlation on most nights. We show that the Cl2 at our site was likely a co-product with ClNO2 from N2O5 uptake on aerosols that contain acidic chloride, rather than being produced by ClNO2 uptake, as previously suggested. The Cl2 yield (φ(Cl2)) derived from the N2O5 uptake hypothesis exhibited significant correlations with [Cl-] and [H+], based on which a parameterization of φ(Cl2) was developed. The derived parameterizations of φ(ClNO2) and φ(Cl2) can be used in models to quantify the nighttime production of ClNO2 and Cl2 and their impact on the next day’s photochemistry.

How to cite: Xia, M., Wang, T., Peng, X., Wang, W., Yu, C., Sun, P., Li, Y., Liu, Y., Xu, Z., Wang, Z., Xu, Z., Nie, W., and Ding, A.: Significant production of ClNO2 and possible source of Cl2 from N2O5 uptake at a suburban site in eastern China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12946,, 2020


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