Competitive reactions of SO₂ and acetic acid on α-Al₂O₃ and CaCO₃ particles

Heterogeneous reactions between gaseous pollutants and mineral particles have gradually become a research hotspot in the field of atmospheric chemistry. In this paper, competitive reactions between SO₂ and acetic acid on the surface of α-Al₂O₃ and CaCO₃ particles were studied by the diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) technique in dark and dry conditions. At the same time, the temporary evolution of the integrated absorbance of acetate and sulfite was investigated to further understand the interaction of SO₂ and acetic acid on the mineral particles. On the surface of α-Al₂O₃ particles, acetate and sulfite can compete for surface-active sites, resulting in a decrease in the total amount of acetates. In dark and dry conditions, the effect of acetic acid on SO₂ cannot be obtained by the DRIFTS method. On the surface of CaCO₃ particles, SO₂ can have a competitive impact on acetic acid by grabbing active sites, leading to a slight decrease of the amount of acetates. The heterogeneous reaction of SO₂ can be impeded by coexisting acetic acid, resulting in a drastic reduction of the number of sulfites. It can be seen that the formation mechanisms of acetate and sulfite on the surface of different mineral particles in the atmosphere are different, which provides a variety of ideas and possibilities for the formation of related inorganic and organic salts in the atmosphere.