Global budgets of atmospheric primary and secondary organic aerosols based on the simulation for full-volatility-range organic precursors

Organic aerosol (OA) is a major component of tropospheric submicron aerosols, influencing air pollution, human health, and climate change. Primary and secondary OA (POA and SOA) exhibit distinct physicochemical properties that lead to different health and climate impacts. Current chemical transport models (CTMs), however, have difficulties not only in capturing OA concentrations, especially in polluted regions, but also in reproducing the fraction of POA and SOA. Here, we develop an OA simulation framework for full-volatility-range organic precursors, with a particular focus on improving OA formation from semivolatile and low-volatility organic compounds (S/LVOC) and intermediate-volatility organic compounds (IVOC), based on the atmospheric chemical transport model GEOS-Chem. Cooperating with a newly developed bottom-up global anthropogenic emission inventory, MEIC-global-FVOC, the improved OA scheme shows a good model performance when evaluated against a comprehensive dataset of worldwide measurements for OC, POA, and SOA, driven by increased POA formation from S/LVOC and SOA formation from IVOC. The model indicates that several populated regions in Asia, Africa, America, and Europe suffer from high OA exposure with annual mean over 5 μg m^-3, highlighting the importance of controlling OA pollution. In East Asia, South Asia, the northern part of Africa, and Europe, anthropogenic SOA and POA are the largest two contributors to OA pollution, suggesting the need for reducing residential combustion that contributes over half of anthropogenic S/LVOC and IVOC emissions. For other regions, most of OA is from natural sources, which may be easily affected by extreme events (e.g., wildfires) and the warming climate. The estimated global OA burden in 2018 is 2.50 Tg, with a fraction of 75% from SOA. The SOA burden is higher than previous estimates, resulting from increased formation of S/LVOC and IVOC, highlighting that the role of SOA should be given more attention in assessing aerosol climate impact. The estimation of OA burden is sensitive to pyrogenic emission estimates and wet deposition parameterization, which need more constraints in future studies.