Simulating secondary organic aerosol formation using the volatility basis-set approach in a chemical transport model

The secondary organic aerosol (SOA) module in PMCAMx, a three-dimensional chemical transport model, has been updated based on laboratory results from recent smog chamber experiments. A new modeling framework is used based on the SOA volatility basis-set approach instead of the two-product approach used in existing models. The different scenarios are simulated for July 2001, and the predicted organic aerosol (OA) concentrations are compared to the available ambient measurements from the EPA Speciation Trends Network (STN) and the Interagency Monitoring of Protected Visual Environments (IMPROVE). The base-case OA simulation slightly overpredicts the ambient measured OA concentrations at the rural IMPROVE monitoring sites with a bias of 0.33 μg m−3. Compared to the urban STN sites, the base-case scenario still underpredicts the observed OA concentrations but is performing significantly better than the two-product module in PMCAMx compared to observations. The contribution of biogenic and anthropogenic SOA to the predicted organic aerosol concentrations and the potential role of chemical aging are investigated. The higher yields of SOA from anthropogenic precursors reported in the most recent studies improve the model performance in urban areas.