Chloric acid-driven nucleation enhanced by dimethylamine and sulfuric acid in the Arctic: mechanistic study

Abstract. Chlorine radicals are strong oxidizing agents in the atmosphere, and the process of chlorine oxidation results in the formation of chloric acid (HClO3, CA). Recent studies have shown that trace amounts of CA have been detected in the Arctic boundary layer. However, the contribution of chlorine-containing species to oceanic new particle formation (NPF) has not been fully revealed. It is speculated that CA is involved in the oceanic nucleation process. In this study, the enhancement of CA-based NPF by dimethylamine (DMA) and sulfuric acid (SA) was comparatively investigated at the molecular level using density-functional theory (DFT) and atmospheric cluster dynamics simulation (ACDC). The results show that DMA can form clusters with CA through hydrogen bonding, halogen bonding and proton transfer, which reduces the energy barrier for CA-based cluster formation and significantly improves the thermodynamic stability of CA clusters. The cluster formation rate of CA-DMA cluster system is higher than that of the CA-SA cluster system. CA-DMA nucleation may not effectively contribute to Arctic NPF. These findings may help to reveal some of the missing sources of the Arctic NPF. The present study contributes to a deeper understanding of the influence of oceanic chlorine-containing constituents on the oceanic NPF.