Simulation of Regional Secondary Organic Aerosol Formation From Monocyclic Aromatic Hydrocarbons using a Near-Explicit Chemical Mechanism Constrained by Chamber Experiments

The formation of secondary organic aerosols (SOA) is inextricably linked to the photo-oxidation of aromatic hydrocarbons. However, models still exhibit biases in representing the mass and chemical composition of SOA. We implemented a box model coupled with a near-explicit photochemical mechanism, the Master Chemical Mechanism (MCMv3.3.1) to simulate a series of chamber studies and access model biases in simulating SOA from representative aromatic hydrocarbons. The box model underpredicted SOA yields of toluene and xylenes by 4.7–100%, which could be improved by adjusting the saturation vapor pressure (SVP) of their oxidation products. After updating the SVP values, the mass concentration of TX SOA in the Yangtze River Delta region during summer was doubled, and there was also an approximated 3% enhancement in the total SOA. In comparison to a lumped mechanism used for simulating TX SOA, MCM predicted similar mass concentrations but exhibited different volatility distributions and oxidation states.