A Study on the Seasonal Correlation between O3 and PM2.5 in Seoul in 2017

To characterize the correlation between tropospheric O-3 and PM2.5 by season, a comprehensive analysis for the interaction between tropospheric O-3 and PM2.5 has been performed over 25 sites in Seoul in 2017. Highly positive correlation between O-3 and PM2.5 was observed during the summer period (June, July, and August) and this is related to the simultaneous formation of O-3 and PM2.5 due to an increase of the atmospheric oxidation ability. While, correlations of O-3 and PM2.5 were negative in the winter period (January, February, and December), showing the opposite trend with summer. The negative correlation for O-3 and PM2.5 in winter might be due to both aerosol-radiation interactions and the O-3 titration effect by NOx. We also found that NOx plays a more significant role to decrease O-3 concentration than PM2.5 on a low concentration of O-3 in winter. It indicates that there are seasonal difference for the mechanisms of O-3 and PM2.5 interaction. Therefore, it is required on a different O-3 and PM2.5 reduction approach for each season.