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

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