Abstract
In this study, domestic and foreign contributions to a severe PM2.5 episode in South Korea, in which “emergency reduction measures against particulate matter” were issued, were analyzed. During the period between 27 February and 7 March in 2019 when high PM2.5 concentrations occurred, the PM2.5 concentration in the Seoul metropolitan area (SMA) in South Korea was approximately 87.3 μg/m3 on average, and a severe PM2.5 concentration level of approximately 113.4 μg/m3 was observed between 3 March and 5 March. The results of the analysis conducted using the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model and meteorological observation data showed that northwesterly wind or westerly winds were formed during the P1 and P3 periods when the PM2.5 concentration markedly increased. When the PM2.5 concentrations in East Asia were simulated using the Community Multiscale Air Quality (CMAQ), it was found that the high PM2.5 concentrations that occurred in the SMA of South Korea were mostly affected by PM2.5 transported over long distances and following atmospheric stagnation. When the domestic and foreign contributions were evaluated using the brute-force method (BFM), the foreign and domestic contribution concentrations were found to be 62.8 and 16.8 μg/m3, respectively, during the target period of this study. It was also found that the foreign contribution was 78.8%, while the domestic contribution was 21.2%.
Highlights
Particulate matter (PM) is a liquid or solid substance with a diameter less than 10 μm suspended in the atmosphere and is defined as PM10 and PM2.5 depending on the diameter
To examine the reliability of the PM2.5 concentration simulated by Community Multiscale Air Quality (CMAQ), statistical verification was performed using R, the root-mean-square error (RMSE), the mean bias error (MBE), the normalized mean bias (NMB), and the index of agreement (IOA)
The PM2.5 spatial distribution simulated through Weather Research and Forecast (WRF) and CMAQ suggests that most of the high PM2.5 concentrations observed in Seoul metropolitan area (SMA) were affected by the trans-boundary air pollutants transported over long distances in Northeast Asia
Summary
Particulate matter (PM) is a liquid or solid substance with a diameter less than 10 μm suspended in the atmosphere and is defined as PM10 and PM2.5 depending on the diameter (particle matter with an aerodynamic diameter less than 10 μm and 2.5 μm, respectively). As northwesterly winds are formed under the influence of migratory anticyclones in spring and autumn and the Siberian anticyclone in winter, South Korea can be affected by trans-boundary. For the establishment of effective PM concentration reduction measures, the quantitative evaluation of the trans-boundary PM transported over long distances and its precursors is required along with the analysis of the influence of weather conditions and major emission sources affecting the generation and removal of PM. They found that foreign emissions affected up to 60% of the annual average PM10 concentration of the Seoul metropolitan area (SMA) and up to 70% in March among the cold seasons (from autumn to spring). Domestic and foreign contributions were estimated by applying BFM to the CMAQ model
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