Ionic Strength Effect Triggers Brown Carbon Formation through Heterogeneous Ozone Processing of Ortho-Vanillin

Methoxyphenols are an important class of compounds emerging from biomass combustion, and their reactions with ozone can generate secondary organic aerosols in the atmosphere. Here, we use a vertical wetted wall flow tube reactor to evaluate effect ionic strength on heterogeneous reaction gas-phase (O3) liquid film o-vanillin (o-VL) (2-hydroxy-3-methoxybenzaldehyde), as proxy for methoxyphenols. Typical moderately acidic aerosols, at fixed pH = 5.6, uptake coefficients (γ) O3 o-VL ([o-VL] 1 × 10–5 mol L–1) increase γ (1.9 ± 0.1) 10–7 absence Na2SO4 (6.8 0.3) I 0.2 L–1, then, it decreases again. The addition NO3– ions only slightly uptakes O3. Ultrahigh-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) reveals that formation multicore aromatic is favored upon o-VL, presence SO42– ions. favors nitrooxy (−ONO2) or oxygenated group organonitrates, which components brown carbon affect both climate air quality.