Air pollutants tamper with energy budget. As a result they change the climate. Also pollutants have an negative effect on ecosystem, cause visibility impairment and adversely affect human health. Air pollution is associated with increasement of premature mortality and cardiovascular disease. Metropolitan cities are densely populated with people and crowded with pollutants sources. Many studies suggest air quality is getting worse, especially in cities. For the constant monitoring of air pollution, K-eco (Korea Environment Corporation) made ground observational network. To mitigate the damage from air pollution, understanding spatiotemporal distribution of pollutants is essential. Meteorological condition should be considered as priority factor to find out the distribution of air pollutants. Under certain meteorological condition, accumulation of pollutants can be accelerated and severe episode can occur. Meteorology can affect on formation of secondary pollutants, which are created from chemical reaction with each other or atmospheric compounds, such as water vapor, O3 and NO. The purpose of this study is to investigate the spatiotemporal (monthly, weekly, diurnal) variability of surface air pollutants (PM10, PM2.5, SO2, NO2, O3, CO), relationship with meteorological condition and meteorological influence on relationship between trace gases (SO2, NO2, O3, CO) and particulate matters (PM10, PM2.5) in seven metropolitan area (Seoul, Incheon, Daejeon, Gwangju, Daegu, Busan, Ulsan).
Surface air pollutants (PM10, PM2.5, SO2, NO2, O3, CO) hourly data measured at urban monitoring network are used for the period of 2015-2017. Hourly meteorological data at each city are used. Five factors, temperature (℃), wind speed (m/s), relative humidity (%), cloud amount (tenth), visibility (m) are used in this study, for same period.
Pollutants’s variability of diverse spatial and temporal scales are analyzed. Most pollutants (PM10, PM2.5, SO2, NO2, O3, CO) have low concentration in summer, and high in winter. O3 is high in spring because of photochemical reaction. To identify anthropogenic effect impacts of air pollutants, APD (Average Percent Departure) and WCI (Weekly Cycle Index) suggested in Georgoulias and Kouridis (2011) are applied. NO2 and O3 show distinct characteristic called weekend effect. PM10, PM2.5, SO2, NO2, CO peak at rush hour (KST 08:00-10:00), whereas O3 does at afternoon (KST 14:00-16:00).
Influences of meteorological variables are examined through the comparison of correlation coefficients between meteorological factors and pollutants. PM10, PM2.5, SO2, NO2, CO have negative correlations with temperature and wind speed, respectively. O3 has distinctive feature, which has positive correlation with temperature and wind speed, while it does negative correlation with relative humidity. O3 characteristics can be explained by photochemical reaction.
We analyzed significance of meteorological condition through qualitative analysis. Meteorological variables are categorized as values. Correlation coefficients of Each meteorological variable group between gas phase pollutants (SO2, NO2, O3, CO) and particulate matters (PM10, PM2.5) are compared. The relationship of O3 and particulate matters (PM10, PM2.5) is sensitive to temperature. They have negative correlation below 0℃ and positive correlation above 20℃. Correlation coefficients between SO2 and particulate matters (PM10, PM2.5) increase when the wind becomes strong. It implies the effect of transport. Few pollutants (SO2, NO2) and PM’s relationship change according to cloud amount. It can be related to cloud chemistry (Cheng et al., 2016).
This study investigated the spatiotemporal variability of surface air pollutants (PM10, PM2.5, SO2, NO2, O3, CO) and provided influence of meteorological variables in metropolitan cities, Korea. For more improvement of this study, wind direction and precipitation will be considered in future.