Effect of Precipitation on Air Pollutant Concentration in Seoul, Korea

Abstract

In this study, long-term rainfall data with irregular spatial distribution in Seoul, Korea, were separated into individual precipitation events by the Inter-event time definition of 6 hours. Precipitation washout of PM10 and NO2 concentrations in the air considering various complex factors were analyzed quantitatively. Concentrations of PM10 and NO2 in the atmosphere were lower under condition of rainfall compared to that of non-precipitation, and a noticeable difference in average PM10 concentrations was observed. The reduction of concentrations of PM10 and NO2 by rainfall monitored at road-side air monitoring sites was also lower than that of urban air monitoring sites due to continuous pollutant emissions by transportation sources. Meanwhile, a relatively smaller reduction of average PM10 concentration in the atmosphere was observed under conditions of light rainfall below 1 mm, presumably because the impact of pollutant emission was higher than that of precipitation scavenging effect, whereas an obvious reduction of pollutants was shown under conditions of rainfall greater than 1 mm. A log-shaped regression equation was most suitable for the expression of pollutant reduction by precipitation amount. In urban areas, a lower correlation between precipitation and reduction of NO2 concentration was also observed due to the mobile emission effect.

Keywords

• precipitation
• inter-event time definition
• air pollution
• pm10
• no2