Atmospheric nitrogen and sulfur containing compounds for three sites of South Korea

Atmospheric concentrations of gaseous HNO3, NH3 and particulates NO3− and SO42− were analyzed at three sites, Chunchon, Seoul and Anmyon-do, on the Korean peninsula by filter pack method. The samples were collected over a period of 24 h every Wednesday. At one of the sites, Chunchon, atmospheric SO2 was measured by using a four-stage filter pack. The annual mean concentrations of HNO3 and NH3 in 1998 ranged from 1.67 to 2.94 and from 2.00 to 3.95 μg m−3, respectively. The annual average of SO2 at Chunchon was 7.32 μg m−3. The annual averages of particulate NO3− and SO42− were 4.83–6.10 and 4.88–7.25 μg m−3, respectively. Particulate SO42− showed no distinct seasonal variation while its primary pollutant, SO2 displayed concentration peak in winter and bottomed out during summer. Consequently, the S(VI)/[S(IV)+S(VI)] ratio increased in a warm and light intensive summer and decreased in the cold and dark winter. This result suggests oxidation reactions were more efficient during the summer than in the winter. HNO3 showed a summer maximum which resulted from the temperature dependence of vapor pressure and oxidation reaction rates of its related compounds. Atmospheric NH3 was elevated in the warmer season, which related to an increase in source strength and vapor pressure. On the other hand, particulate NO3− and NH4+ showed either winter peaks or no seasonal variation. These seasonal trends in nitrogen related compounds can primarily be explained by the gas–particle conversion reaction of NH4NO3 to NH3 and HNO3. This fact is supported by an increase in the ratio of gaseous nitrogen to particulate nitrogen as the ambient temperature rose.