Age evolution of secondary organic aerosol: Impacts of regional transport and aerosol volatility

In this study, a revised CMAQ model incorporating source and temporal apportioning functions has been used to analyze the aging characteristics of SOA in East Asia. The results show that in the aerosol phase, the fraction of the non-volatile components typically fluctuates around 75 %-95 %, and aromatic hydrocarbon precursors contribute significantly to SOA, accounting for 45.6 %-72.7 % in winter and 29.1 %-52.7 % in summer. Transport due to meteorological conditions does not affect the SOA volatility profile in the cities, while regional source composition has been found to be important for the characterization of the properties of SOA in cities. When the SOA regional composition type is a multi-region-imported-dominated type (MRT), its age composition type tends to be an old-age-SOA-dominated type (OAT) (>48 h). Additionally, transport also causes fluctuations in the range of hourly SOA with atmospheric age of 96 h or higher. The SOAs normally transport through seasonal monsoon and could migrate longer in winter (700-1500 km in January) than in other seasons (250-900 km in April; 500-1200 km in July; 300-1000 km in October). Additionally, in winter, non-volatile SOA generally has a longer transport distance (700-1600 km) than semi- and low-volatile SOA (300-1300 km and 600-1500 km). Furthermore, during the transport process, geographical barriers have negligible impact on SOA in the 48+ hour age group.