SOA formation from complex anthropogenic hydrocarbon mixtures: modeling from laboratory to regional scales

Secondary organic aerosol (SOA) in urban environments is formed primarily from the photooxidation of a diverse set of alkane and aromatic hydrocarbons (HCs) due to the emissions from anthropogenic activity. This study employs parameters of alkane and aromatic HCs to simulate SOA formation from complex anthropogenic hydrocarbon mixtures using the Unified Partitioning and Aerosol Phase Reaction (UNIPAR) model. The model is demonstrated against SOA chamber data collected under various NOx and seed conditions. Measured SOA yields were significantly enhanced in lower NOx experiments, while they were not significantly impacted by inorganic seed conditions. When concentrations of alkanes and aromatics were similar, model simulations indicated that the majority (60–80%) of SOA formation originated from alkanes. The importance of alkanes as the key anthropogenic SOA precursor was also demonstrated via regional simulations using the CAMx-UNIPAR model. In Seoul, South Korea, aromatics and alkanes accounted for 59.1% and 36.8% of the total VOC emissions while producing 18.2% and 53.8% of the total SOA, respectively. Terpene precursors were demonstrated to have high SOA formation capabilities in the NOx-rich atmosphere of Seoul. Simulation results suggest that the reduction of NOx concentrations in extremely high NOx environments may lead to lower SOA mass production, even while the yields of anthropogenic precursors increase gradually, due to the considerable reduction of terpene SOA yields. The complex influence of future temperature increases on SOA formation is discussed due to its influence on anthropogenic precursor partitioning, biogenic precursor emissions, oxidation conditions, and oxidized product partitioning.Copyright © 2026 American Association for Aerosol Research