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  Impact of non-ideality on reconstructing spatial and temporal variations of aerosol acidity with multiphase buffer theory

Zheng, G., Su, H., Wang, S., Pozzer, A., & Cheng, Y. (2021). Impact of non-ideality on reconstructing spatial and temporal variations of aerosol acidity with multiphase buffer theory. Atmospheric Chemistry and Physics Discussions, 21. doi:10.5194/acp-2021-55.

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 Creators:
Zheng, Guangjie1, Author              
Su, Hang1, Author              
Wang, Siwen1, Author              
Pozzer, Andrea2, Author              
Cheng, Yafang1, Author              
Affiliations:
1Multiphase Chemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826290              
2Atmospheric Chemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826285              

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 Abstract: Aerosol acidity is a key parameter in atmospheric aqueous chemistry and strongly influence the interactions of air pollutants and ecosystem. The recently proposed multiphase buffer theory provides a framework to reconstruct long-term trends and spatial variations of aerosol pH based on the effective acid dissociation constant of ammonia (Ka,NH3*). However, non-ideality in aerosol droplets is a major challenge limiting its broad applications. Here, we introduced a non-ideality correction factor (cni) and investigated its governing factors. We found that besides relative humidity (RH) and temperature, cni is mainly determined by the molar fraction of NO3− in aqueous-phase anions, due to different NH4+ activity coefficients between (NH4)2SO4− and NH4NO3-dominated aerosols. A parameterization method is thus proposed to estimate cni at given RH, temperature and NO3− fraction, and is validated against long-term observations and global simulations. In the ammonia-buffered regime, with cni correction the buffer theory can well reproduce the Ka,NH3* predicted by comprehensive thermodynamic models, with root-mean-square deviation ~0.1 and correlation coefficient ~1. Note that, while cni is needed to predict Ka,NH3* levels, it is usually not the dominant contributor to its variations, as ~90 % of the temporal or spatial variations in Ka,NH3* is due to variations in aerosol water and temperature.

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Language(s): eng - English
 Dates: 2021-04-12
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: No review
 Identifiers: DOI: 10.5194/acp-2021-55
 Degree: -

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Title: Atmospheric Chemistry and Physics Discussions
  Abbreviation : Atmos. Chem. Phys. Discuss.
Source Genre: Journal
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Publ. Info: Katlenburg-Lindau, Germany : European Geophysical Society, Copernicus Publ.
Pages: 29 Volume / Issue: 21 Sequence Number: - Start / End Page: - Identifier: ISSN: 1680-7367
CoNE: https://pure.mpg.de/cone/journals/resource/111076360006006