Mechanistic insights into marine boundary layer nucleation: synergistic interactions of typical sulfur, iodine, and nitrogen precursors

Abstract. Marine new particles have significant impacts on the global atmosphere, yet the key nucleation process underlying their formation remains highly unclear. Given the coexistence of multiple marine nucleating agents, here we explored how typical sulfur-, iodine-, and nitrogen-bearing chemicals, i.e., methanesulfonic acid (MSA), iodic acid (IA), and dimethylamine (DMA), synergistically interact to drive particle nucleation at the molecular level, by high-level quantum chemical calculations and cluster dynamics simulations. The results show that IA, MSA, and DMA can form stable pre-nucleation clusters via intermolecular hydrogen bonding and halogen bonding, with acid-base reactions occurring during their clustering, yielding ion pair formation. The proposed IA–MSA–DMA ternary nucleation is thermodynamically more favorable in regions rich in sulfur and nitrogen but poor in iodine. The cluster formation rate of IA–MSA–DMA ternary system is notably higher than that of any corresponding binary nucleation, showing a synergistic enhancement on rate of 4–8 orders of magnitude. Moreover, this rate even exceeds that of the well-established efficient iodine oxoacids nucleation under sulfur-rich conditions. In polar coastal regions such as Aboa and Marambio, the simulated rates of IA–MSA–DMA nucleation better agree with field measurements compared with the established IA–DMA nucleation. Accordingly, the proposed IA–MSA–DMA nucleation mechanism is expected to be important in the marine boundary layer, helping to explain the missing sources of iodic acid particles, especially in cold polar marine regions. Incorporating this mechanism into the atmospheric modeling can potentially improve aerosol formation simulations and refine climate predictions.