In this study, the contributions of emissions (foreign and domestic) and atmospheric physical and chemical processes to PM2.5 concentrations were evaluated during a high PM2.5 episode (March 24-26, 2018) observed on Korea in the spring of 2018. These analyses were performed using the community multi-scale air quality (CMAQ) modeling system with the brute-force method and the integrated process rate (IPR) analysis, respectively. The contributions of long-range transport (LRT) from China (70-76%) for SMA (Seoul Metropolitan Area) were significantly larger than those (26-56%) of domestic emissions in South Korea. The contributions of LRT from China (68-74%) for Busan Island were significantly larger than those (53-60%) of domestic emissions in South Korea. The contributions of LRT from China (81-89%) for Jeju Island were significantly larger than those (41-45%) of domestic emissions in South Korea.
The substantil contribution of LRT of SMA was confirmed in conjunction with the air mass trajectory analysis, indicating that the frequency of airflow from China (57% of all trajectories) was higher than from other regions (e.g., South Korea) larger than those (41-45%) of domestic emissions in South Korea. The substantil contribution of LRT of BMA (Busan Metropolitan Area) was also confirmed in conjunction with the air mass trajectory analysis, indicating that the frequency of airflow from China (57% of all trajectories) was higher than from other regions. The large contribution of LRT was also confirmed in conjunction with the air mass trajectory analysis in Jeju region, indicating that the frequency of airflow from China (58% of all trajectories) was higher than those (31%) of other regions. These results imply that Chinese emissions have a stronger impact than domestic emissions on the high PM2.5 concentrations in the study area. From the IPR analysis, the contribution of horizontal transport, aerosol process and vertical transport to PM2.5 concentrations were dominant in most of the areas of urban and background areas during the high PM2.5 episode.