EGU21-9292
https://doi.org/10.5194/egusphere-egu21-9292
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

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

Yafang Cheng1, Guangjie Zheng1, Hang Su2, Siwen Wang2, and Andrea Pozzer3
Yafang Cheng et al.
  • 1Minerva Research Group, Max Planck Institute for Chemistry, Mainz 55128, Germany
  • 2Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany
  • 3Air Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany

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.

How to cite: Cheng, Y., Zheng, G., Su, H., Wang, S., and Pozzer, A.: The impact of non-ideality on reconstructing spatial and temporal variations of aerosol acidity with multiphase buffer theory, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9292, https://doi.org/10.5194/egusphere-egu21-9292, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.