Perchloric acid (HClO₄) Drives Atmospheric New Particle Formation Enhanced by Dimethylamine, ammonia and Sulfuric Acid: Mechanisms and Implications

Abstract. Recent studies have revealed observations of atmospheric perchloric acid (HClO₄, PA) in the Arctic. There are few studies of PA forming aerosol particles in coastal marine regions. We use quantum chemical calculations and Atmospheric Clusters Dynamic Code (ACDC) to compare the enhancement potential of dimethylamine (DMA), ammonia (NH₃), and sulfuric acid (SA) for PA-based new particle formation (NPF). The results show that DMA and NH₃ can strongly interact with PA in both directions through hydrogen bonding and proton transfer. Halogen bonding is not found in PA-DMA and PA-NH₃ clusters. Even if the concentration of NH₃ exceeds that of DMA by 10–100 orders of magnitude, the cluster formation rate of PA-DMA cluster formation is much higher than that of the PA-NH₃ cluster system. Clusters with the same number of PA molecules as DMA molecules play a key role in the growth of PA-DMA clusters. Compared with the nucleation of PA with SA, PA nucleates more easily with alkaline gas. The present results reveal the potential for new particle formation of PA in the Arctic boundary layer.