Laboratory-measured Nucleation Rates of Sulfuric Acid and Water from the SO2 + OH Reaction

Binary homogeneous nucleation of H₂SO₄/H₂O is the most basic nucleation system, yet its nucleation mechanisms are poorly understood. Here, we present results of the laboratory study of this binary nucleation system. H₂SO₄was produced through the reaction of SO₂ + OH→ HSO3 (R1) in the presence of SO₂, OH, O2, and H₂O in a fast flow reactor at 288K and atmospheric pressure. OH was produced from the photolysis of H₂O. The power dependence of the nucleation rate (J) on sulfuric acid concentration ([H₂SO₄]) was 2–10 in the [H₂SO₄] range from 3 × 106− 2 × 109 cm−3. This power dependence increased with decreasing RH and increasing nucleation time. The measured aerosol sizes ranged from 4–20 nm. These aerosol sizes were larger at higher [H₂SO₄] and higher RH, and with higher nucleation times. The effects of RH on aerosol growth were also more pronounced at higher [H₂SO₄] and with higher nucleation times.

Keywords Binary nucleation, sulfuric Acid, CIMS