Heterogeneous Chemistry of Glyoxal on Acidic Solutions. An Oligomerization Pathway for Secondary Organic Aerosol Formation

The heterogeneous chemistry of glyoxal on sulfuric acid surfaces has been investigated at various acid concentrations and temperatures, utilizing a low-pressure fast flow laminar reactor coupled to an ion drift-chemical ionization mass spectrometer (ID-CIMS). The uptake coefficient (γ) of glyoxal ranges from (1.2 ± 0.06) × 10–2 to (2.5 ± 0.01) × 10–3 for 60–93 wt % H2SO4 at 253–273 K. The effective Henry’s Law constant (H*) ranges from (98.9 ± 4.9) × 105 to (1.6 ± 0.1) × 105 M atm–1 for 60–93 wt % at 263–273 K. Both the uptake coefficient and Henry’s Law constant increase with decreasing acid concentration and temperature. Our results reveal a reaction mechanism of hydration followed by oligomerization for glyoxal on acidic media, indicating an efficient aqueous reaction of glyoxal on hygroscopic particles leading to secondary organic aerosol formation.