Impacts of emissions and new parameters on the formation of secondary organic carbons

Abstract

Organic aerosols (OAs) account for a large portion of the particulate matter (PM), and in East Asia, where population density is high, high concentrations of NOx, SO2, and NH3 conditions are formed and the production of organic aerosols increases. However, since secondary organic aerosols (SOAs) in the atmosphere are produced through a complex process, chemical transport model (CTM) underestimates SOAs, and an accurate method of parameterizing SOAs is needed to reproduce concentration of SOAs in the model. In this study, a comparative analysis was conducted with the organic aerosol concentration measured in 8 supersites during KORUS-AQ period and the simulated values in CMAQ model. We newly applied emission inventories, SOAs yield data, and enthalpies of vaporization to improve the underestimation of the model. KORUS v1.0 and KORUS v5.0 were used as the emission inventory, and SOA yields were calculated according to East Asian atmospheric conditions in the chamber study. In addition, enthalpies of vaporization applied data calculated through molecular dynamics simulation. In the case of the emission inventory, when KORUSv5.0 was used in the model simulation, the gas phase simulation accuracy was increased and the underestimation was also improved. Comparing the simulated OAs concentration with the observed OAs concentration, it is found that mean bias range according to the experiment is -0.75 μg m-3 to 0.50 μg m-3, and it was found that the newly applied SOA parameterization method significantly improves the underestimation of the model. When evaluating the degree of improvement in underestimation for low- and high-concentration episodes, we found that the concentration of BSOC was an important factor in underestimation improvement. In conclusion, the application of SOA yield data calculated in accordance with East Asian atmospheric conditions and enthalpy of vaporization calculated through molecular dynamics can improve underestimation in model simulation. However, differences in the amount of increase may occur depending on the composition of organic aerosol, and in the case of BSOC, the increase in concentration was the largest, but seasonal and meteorological factors cannot be excluded, so a sensitivity test is required.