Physicochemical Characteristics of PM_2.5 Based on Long-term Hourly Data at National Intensive Monitoring Sites in Korea

The objective of this study was to analyze the temporal and spatial characteristics of fine particle matters by using huge hourly datasets of PM_2.5, including chemical information monitored at the 6 national intensive monitoring sites (NIMSs) from 2013 to 2018 in Korea. Hourly PM_2.5 raw datasets were obtained from the National Institute of Environmental Research (NIER) in Korea. Monitoring sites included urban, rural/agricultural, industrial, and marine environments. Since the PM_2.5 concentration steadily decreased nationwide, each species concentration also decreased in general. One of key reasons for decreasing PM_2.5 might be explained by the implementation of domestic fine dust reduction policies and external influences such as PM_2.5 concentration reduction in China. It was observed that 45.0% of all datasets for 6 years were classified as good condition. The average sum of 14 elements over all sites in 2018 was calculated to be 501.5 ng/m³, and its mass ratio for PM_2.5 (21.9 μg/m³) was 2.30%. The inorganic elements were generally higher in industrial/urban areas than in agricultural areas. In addition, the average TC (total carbon) over all 6 sites was 28.3% of PM_2.5 with the range of 23.6% to 31.4%. The TC in small urban areas was much higher than that in marine areas or even that in large, populated urban area/industrial areas. It seemed that the latter areas were better controlled than the former area in terms of combustion activities of fossil fuels.