Response of biogenic secondary organic aerosol formation to anthropogenic NOx emission mitigation

In the 3-D simulations conducted for the summer of 2018 over Europe, the implementation of GBM significantly improved the model ' s performance in comparison to simulations using the H 2 O mechanism, yielding results more consistent with measured aerosol concentrations extracted from the EBAS database. In response to NOx emission mitigation, simulated SOA concentrations increase with GBM but decrease when using the H 2 O mechanism, unless a highly oxygenated molecules (HOMs) formation scheme is incorporated.

The SOA composition becomes more oxidized and concentrations elevate after NOx reduction, particularly in simulations using GBM. These higher concentrations are likely due to enhanced reaction rates of organic peroxy radicals (RO 2 ) with HO 2 , resulting in more oxidized products from monoterpene degradation that favors HOM formation. The results suggest that detailed SOA mechanisms including autoxidation are necessary for accurate predictions of SOA concentrations in 3-D modeling.