Temporal and Spatial Variations of NOx and Ozone Concentrations in Seoul during the Solar Eclipse of 22 July 2009

Abstract

The temporal and spatial variations of NO, NO2, and O-3 concentrations in Seoul, South Korea, during the solar eclipse of 22 July 2009 are investigated by analyzing data measured at 25 environmental monitoring stations. The NO2 concentration increases and the NO and O-3 concentrations decrease because the efficiency of NO2 photolysis decreases during the solar eclipse. About an hour after the maximum obscuration, the reduction in the average O-3 concentration over Seoul is estimated to be 45%. The maximum reduction in the O-3 concentration downwind of the NOx source area is higher and occurs later than that in the downtown region. Deviations from the NO-NO2-O-3 photostationary state in the downwind region are larger than those in the downtown region. This result implies that, in addition to the photochemical effect, the effect of transport by winds increases the reduction potential of the O-3 concentration in the downwind region during the solar eclipse.