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.