The Role of Sulfuric Acid in Atmospheric Nucleation

TLDR

Gas‑phase sulfuric acid is key to atmospheric particle formation, yet laboratory nucleation rates with water are far too low to explain observed particle concentrations. The study demonstrates that sulfuric acid nucleates with water at rates sufficient to explain atmospheric particle abundance, producing 1–2 molecule particles as small as 1.5 nm that were previously undetectable. Citation: Sipilä et al.

Abstract

Little Things Do Matter Gas-phase sulfuric acid is important during atmospheric particle formation, but the mechanisms by which it forms new particles are unclear. Laboratory studies of the binary nucleation of sulfuric acid with water produce particles at rates that are many orders of magnitude too small to explain the concentration of sulfuric acid particles found in the atmosphere. Sipilä et al. (p. 1243 ) now show that gas-phase sulfuric acid does, in fact, undergo nucleation in the presence of water at a rate fast enough to account for the observed abundance of sulfuric acid particles in the atmosphere. These particles, which contain 1 to 2 sulfuric acid molecules each, were not detectable previously, owing to their small size, with diameters as small as 1.5 nanometers.