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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-85
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Technical note
02 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Technical note: Comparison and interconversion of pH based on different standard states for aerosol acidity characterization
Shiguo Jia1,2, Xuemei Wang3, Qi Zhang1, Sayantan Sarkar4, Luolin Wu1, Minjuan Huang1,2, Jinpu Zhang5, and Liming Yang6 1School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou, 510275, P. R. China
2Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou 510275, P. R. China
3Institute for Environmental and Climate Research, Jinan University, Guangzhou 510632, P. R. China
4Department of Earth Sciences, Indian Institute of Science Education and Research – Kolkata, Nadia 741246, West Bengal, India
5Guangzhou Environmental Monitoring Center, Guangzhou, 510030, P. R. China
6Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117576
Abstract. Aerosol pH is often calculated based on different standard states thus making it inappropriate to compare aerosol acidity parameters derived thereby. Such comparisons are however routinely performed in the atmospheric science community. This study attempts to address this issue for the first time by providing a theoretical framework to compare and convert between aerosol pH values calculated based on molarity, molality and mole fractions. Using hourly ionic species measurements in Guangzhou, China, it is observed that pHx (mole fraction based) is always 1.74 pH unit higher than pHm (molality based) and follow the same trend, regardless of aerosol property. The difference between pHx and pHc (molarity based), on the other hand, ranges from 1.74 to 1.89 depending on the density of hygroscopic aerosol. It is observed that application of this pH standardization protocol can significantly influence conclusions on aerosol acidity reported by past studies and is thus highly recommended.

Citation: Jia, S., Wang, X., Zhang, Q., Sarkar, S., Wu, L., Huang, M., Zhang, J., and Yang, L.: Technical note: Comparison and interconversion of pH based on different standard states for aerosol acidity characterization, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-85, in review, 2018.
Shiguo Jia et al.
Shiguo Jia et al.
Shiguo Jia et al.

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Short summary
Aerosol pH are often directly compared while ignoring the inconsistency in standard states. This study attempts to address this issue by providing a theoretical framework to compare and convert between aerosol pH values calculated based on different standard states. It is observed that application of this pH standardization protocol can significantly influence conclusions on aerosol acidity reported by past studies and is thus highly recommended.
Aerosol pH are often directly compared while ignoring the inconsistency in standard states. This...
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