The seasonal characteristics of atmospheric particulate matter (PM) were evaluated through the measurement of PM10(particles with an aerodynamic diameter of less than 10 μm) and PM2.5 (particles with an aerodynamic diameter of less than 2.5 μm) collected in the downtown area of Iksan city over roughly two weeks in each season of 2004. During the sampling period, 54 samples of PM10 and PM2.5 were collected and then measured for mass concentrations of PM and its water-soluble inorganic ion species. The concentrations of PM10 and PM2.5 were highly variable on a daily time scale in all seasons, especially in fall. Annual concentrations of PM10 and PM2.5 were 54.7±21.6 μg/m3 and 34.0±13.4 μg/m3, respectively. The daily concentrations of the analyzed ions similarly showed a pronounced variation, although a difference between seasons existed. Among them, SO42−, NO3− and NH4 + were the most abundant ions in all seasons, contributing up to 32% of PM10 and 39% of PM2.5. The contribution of SO42− and NO3− showed a seasonal variation, as SO42− was the highest during spring and summer and NO3 − was the highest during fall and winter. Non-seasalt SO42−and NO3− were found to exist mainly as neutralized chemical components of (NH4)2SO4 and NH4NO3 due to the high concentration of NH4 + in PM samples, which were a major form of airborne PM in all seasons. Seasonal characteristics of PM10 and PM2.5 in Iksan were described in relation to the temporal variations of daily concentration of PM and its inorganic ion species including inter-particle reactions
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