HIO3–HIO2-Driven Three-Component Nucleation: Screening Model and Cluster Formation Mechanism

Iodine oxoacids (HIO₃ and HIO₂)-driven nucleation has been suggested to efficiently contribute to new particle formation (NPF) in marine atmospheres. Abundant atmospheric nucleation precursors may further enhance HIO₃-HIO₂-driven nucleation through various multicomponent nucleation mechanisms. However, the specific enhancing potential (EP) of different precursors remains largely unknown. Herein, the EP-based screening model of precursors and enhancing mechanism of the precursor with the highest EP on HIO₃-HIO₂ nucleation were investigated. The formation free energies (ΔG), as critical parameters for evaluating EP, were calculated for the dimers of 63 selected precursors with HIO₂. Based on the ΔG values, (1) a quantitative structure-activity relationship model was developed for evaluating ΔG of other precursors and (2) atmospheric concentrations of 63 (precursor)₁(HIO₂)₁ dimer clusters were assessed to identify the precursors with the highest EP for HIO₃-HIO₂-driven nucleation by combining with earlier results for the nucleation with HIO₃ as the partner. Methanesulfonic acid (MSA) was found to be one of the precursors with the highest EP. Finally, we found that MSA can effectively enhance HIO₃-HIO₂ nucleation at atmospheric conditions by studying larger MSA-HIO₃-HIO₂ clusters. These results augment our current understanding of HIO₃-HIO₂ and MSA-driven nucleation and may suggest a larger impact of HIO₂ in atmospheric aerosol nucleation.