Spatio-temporal changes of PM10 trends in South Korea caused by East Asian atmospheric variability

Abstract

Atmospheric dust loadings strongly depend on the amount of dust emissions and on the atmospheric variability. This study examines trends in PM10 (i.e., a particulate matter with the aerodynamic diameter equal to or less than 10 μm) mass concentrations for South Korea with respect to the East Asian atmospheric variability due to climate warming. The PM10 mass concentrations were used by the nationwide monitoring network of the Korean Ministry of Environment (KME) over the two-decade period of 1999–2018. Annual PM10 in South Korea was found to decrease to −0.61±0.08 μg m⁻³ yr⁻¹ over the two decades of 1999–2018. Such an overall decrease was more associated with a decreasing trend during spring and summer than during other seasons. An empirical orthogonal function (EOF) analysis of wind speed at 850 hPa accounted for the spatial structure wherein the decrease of wind speeds in Mongolia and China was consistent with those in South Korea during the spring season. Furthermore, the next highest PM10 reduction rate during the stagnant and humid summer period was caused by a warmer air mass over the northwest Pacific Ocean. In eastern China, the annual aerosol optical depth (AOD) reflected by primary and secondary particulate matters showed high values and increased to 0.01 (r²=0.60) for the period of 2000–2013. However, annual AOD values increased negligibly in the Yellow Sea and the Korean Peninsula due more likely to decreasing wind speeds from eastern China. The policy limiting emissions in China since 2014 as well as continuous efforts to reduce air pollution in South Korea affected the AOD decreasing trend. Therefore, the reduced transport and local emissions most likely explain the sharp decreasing trends of PM10 in South Korea during the recent 5-year period of 2014–2018.