Characteristics of atmospheric hydrogen peroxide variations in Seoul megacity during 2002–2004

Atmospheric hydrogen peroxides (H2O2) and methyl hydroperoxide (CH3OOH) were measured in Seoul, the capital of South Korea. Experiments were performed for several days almost every month from January 2002 to April 2004. Gaseous hydroperoxide was collected in aqueous solution and determined by HPLC-fluorescence method. In general, the higher levels of H2O2 were found in warm and humid air with high ozone concentrations, but lower concentrations of SO2, NO2, CO and PM10. For two-year measurements, seasonal factor was the most dominant and the concentrations of H2O2 were highest in summer, for which the median, mean, and upper 90% values were 0.53 ppbv, 0.81 ppbv, and 1.61 ppbv, respectively. In highly polluted metropolitan Seoul, the photochemical activity controlling H2O2 variations was seemingly more sensitive to meteorological conditions than the level of chemical pollutants. It was mainly due to high emissions of pollutants, particularly NOx, which was demonstrated by the occasional occurrence of CH3OOH.