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

Abstract

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.