Crop Residue Burning in Northeast China and Its Impact on PM2.5 Concentrations in South Korea

The impact of crop residue burning in northeastern China on South Korean PM2.5 concentrations was assessed via weather conditions, air quality modeling (AQM), and PM2.5 composition data during two cases exceeding 35 µg·m−3 in November 2015. PM2.5 concentration simulations of Case 1 differed from observations by 3.7–17.6 µg·m−3, overestimating the levels by 6–36%; however, Case 2 varied by 20.0–59.8 µg·m−3 from observations, with a 53–91% underestimation. Case 1 was generally well simulated, whereas the Case 2 simulation failed because the emissions of crop residue burning in northeastern China, as confirmed through satellite analysis (MODIS fires and thermal anomalies) and previous research, were not considered. The portion of organic/elemental carbon ratio during Case 2 was 1.6–2.3 times higher than that of Case 1. These results suggest that it is necessary to consider the effects of crop residue burning in northeast China to establish countermeasures to improve air quality and air quality forecasting in South Korea.