Effects of transboundary PM(2.5) transported from China on the regional PM(2.5) concentrations in South Korea: A spatial panel-data analysis

This study identifies causal links between a high-PM(2.5) episode in Korea and air pollutants originating from China during a high-PM(2.5) episode that occurred in Korea between February 23 and March 12, 2019. Datasets on ground-based PM(2.5) levels in Korea and China, airflows from the back-trajectory models, and satellite images were investigated, and long-range transboundary transport (LRTT) effects were statistically analyzed using spatial panel-data models. The findings are: 1) visual presentations of the observed PM(2.5) concentration in China and Korea, back-trajectory air flows, and satellite images from the Moderate Resolution Imaging Spectroradiometer Aerosol Optical Depth and the Copernicus Atmosphere Monitoring Service clearly show that transboundary air pollutants from China affect PM(2.5) concentration in Korea; 2) the effect of LRTT from China is likely to intensify under certain meteorological conditions, such as westerly winds from China to Korea, the formation of high pressure in China and low pressure in Korea, relatively high temperature, and stagnant air flow in Korea; 3) the results from the spatial panel-data models provide statistical evidence of the positive effect of LRTT from China on increasing local PM(2.5) concentration in Korea. The nationwide average LRTT contributions to PM(2.5) concentration in Korea are 38.4%, while regional contributions are 41.3% for the Seoul Metropolitan Area, 38.6% for the northwest region, and 27.5% for the southeast regions in Korea, indicating the greatest impact on the Seoul Metropolitan Area.