The vital role of sulfuric acid in iodine oxoacids nucleation: impacts of urban pollutants on marine atmosphere

The nucleation of iodic acid (HIO₃) and iodous acid (HIO₂) play a significant role in marine new particle formation (NPF) events. However, the inability to explain intensive NPF bursts in polluted coasts indicates the participation of potential precursors. Herein, we identified a novel nucleation mechanism of HIO₃-HIO₂ system enhanced by the urban pollutant sulfuric acid (H₂SO₄). We found that H₂SO₄ could largely enhance the cluster formation rates (J, cm⁻³ s⁻¹) of HIO₃-HIO₂ system, especially in high [H₂SO₄] regions near H₂SO₄ emission sources. The enhanced J of HIO₃-HIO₂-H₂SO₄ system performs better match than that of HIO₃-HIO₂ system with the observational rates of polluted coasts and polar regions, such as Zhejiang and Marambio. Moreover, the H₂SO₄-involved cluster formation is realized without Gibbs free energy barrier and dominate broadly in marine regions with rich H₂SO₄ and scarce iodine concentrations. These findings may help to explain some missing fluxes of marine new particles and emphasize the impact of urban components on marine nucleation processes.