Temporal variability of surface air pollutants in megacities of South Korea

This study investigated the various temporal (weekly, monthly, and inter-annual) variability of air pollutants (PM10, SO2, NO2, O-3, CO) in seven megacities in South Korea (Seoul, Busan, Incheon, Daegu, Gwangju, Daejeon, and Ulsan). We found that the general decreasing trend of PM10, SO2, NO2, and CO. An exceptional pollutant is O-3, showing a clear increasing trend consistently in all seven megacities. Seasonally PM10, SO2, NO2, and CO have the highest level in winter due to the large fossil-fuel combustion for the heating demand, but O-3 shows the maximum peak in summer related to the intensified photochemistry. Based on the analysis for percentile values of air pollutants, we recognized that some patterns of air pollutants in Korean megacities are overlooked: O-3 increase is not perfectly related to the NO2 pattern, somewhat high SO2 in the coastal cities, ambiguous weekly pattern on Monday (as a weekday) and Sunday (as a weekend). Through this comprehensive analysis of multiple air pollutants using the percentile values, the characteristic for various temporal change of air pollutants in Korean megacities can be better understood, and some useful ideas for the air quality control in the urban region can be also excavated.