The synergistic nucleation of iodous acid and sulfuric acid: A vital mechanism in polluted marine regions

The new particle formation occurs frequently in polluted marine regions, which is related to urban pollutants such as sulfuric acid (H₂SO₄). However, current H₂SO₄-based nucleation mechanism can seldom explain the concentrations of particles in polluted marine regions. Iodous acid (HIO₂) can stabilize iodic acid (HIO₃) clusters through its basic property. Nevertheless, whether HIO₂ could nucleate with H₂SO₄ and the corresponding mechanism are still unknown. Using theoretical calculations, we find that HIO₂ and H₂SO₄ can form stable binary clusters through hydrogen bonds, halogen bonds and acid-base proton transfer. The formation pathways of HIO₂–H₂SO₄ contribute over 73% to the total cluster formation rates (J). Moreover, the J of HIO₂–H₂SO₄ is at least two orders of magnitude higher than that of HIO₃–H₂SO₄ and comparable with the critical HIO₂–HIO₃ system. The HIO₂–H₂SO₄ nucleation may explain some missing fluxes of new particles and expand the H₂SO₄-based nucleation mechanism in polluted marine areas.