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

Abstract The nucleation of iodic acid (HIO 3 ) and iodous acid (HIO 2 ) 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 HIO 3 –HIO 2 system enhanced by the urban pollutant sulfuric acid (H 2 SO 4 ). We found that H 2 SO 4 could largely enhance the cluster formation rates ( J , cm −3 s −1 ) of HIO 3 –HIO 2 system, especially in high [H 2 SO 4 ] regions near H 2 SO 4 emission sources. The enhanced J of HIO 3 –HIO 2 –H 2 SO 4 system performs better match than that of HIO 3 –HIO 2 system with the observational rates of polluted coasts and polar regions, such as Zhejiang and Marambio. Moreover, the H 2 SO 4 -involved cluster formation is realized without Gibbs free energy barrier and dominate broadly in marine regions with rich H 2 SO 4 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.