Title: Studying the effect of gaseous pollutant abatement on aerosol acidity and particle number concentration in Beijing-Tianjin-Hebei

Authors: Wei Zhe; Norhaslinda Monhamed Tahrin

Addresses: School of Physics, Universiti Sains Malaysia, 11800, Pulau Pinang, Malaysia ' School of Physics, Universiti Sains Malaysia, 11800, Pulau Pinang, Malaysia

Abstract: Aerosol acidity is a key physical parameter that critically influences the heterogeneous reactions in the aqueous phase of atmospheric particles. To investigate the impact of precursor reductions (SO₂, NH₃ and NO_X) on the aerosol acidity in Beijing-Tianjin-Hebei, this study used the aerosol thermodynamic model ISORROPIA II to calculate pH values. The results indicated that aerosol acidity in the region was moderately acidic, with an average pH of 4.7 in the base scenario. Due to multiphase buffering effects, pH decreased by 0.7 from the base scenario to 30%_SO₂_40%_NH₃_40%_NO_X and gradually declined from 4.6 to 4.4 across the height range from Eta-1 to Eta-9. Additionally, pH exhibited a parabolic relationship with particle number concentration, peaking at a pH of 4.4.

Keywords: pH; WRF-Chem; Beijing-Tianjin-Hebei; ISORROPIA II; PM_2.5; NH₃; particle number concentration.

DOI: 10.1504/IJEP.2025.148723

International Journal of Environment and Pollution, 2025 Vol.75 No.2, pp.133 - 148

Received: 02 Aug 2024
Accepted: 08 Apr 2025
Published online: 21 Sep 2025 *

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