Objectives: This paper aims to investigate the seasonal deposition characteristics of water-soluble ion species by comparing the deposition amount of two samples taken according to different sampling methods of deposition for ambient aerosol such as gases and particulate matters.Methods: Deposition samples were collected using two deposition gauges in the downtown area of Iksan City over approximately two weeks of each season in 2004. The type of deposition gauges consisted of two different sampling methods known as dry gauge and a wet gauge. The dry gauge was empty and used a dry PE bottle with an inlet diameter of 9.6 cm. Before the beginning of each deposition sampling, a volume of 30-50 ml distilled ionized water was added to the wet gauge to wet the bottom during the sampling period. Deposition samples were measured twice per day and analyzed for inorganic water-soluble ion species using ion chromatography.
Results:The daily deposition amounts of all measured ions in the dry gauge and the wet gauge showed a significant increase when precipitation occurred, having no difference of deposition amount between in the wet gauge and in the dry gauge. By excluding two samples from rainy days during the sampling period, the mean daily deposition of all ions in dry gauge and wet gauge were 6.58 mg/m 2 /day and 18.16 mg/m 2 /day, respectively. The mean deposition amounts of each ion species were higher in the wet gauge than in the dry gauge because of the surface difference of the sampling gauge, especially for NH 4 + and SO 4 2-. The mean deposition amounts of NH 4 + and SO 4 2-in the wet gauge were found to be about 15.4 times and 5.2 times higher than that in dry gauge, with a pronounced difference between spring and summer, while the remaining ion species were 1.1-2.0 times higher in the wet gauge than in the dry gauge. Dominant species in the dry gauge were Ca 2+ and NO 3 -, accounting for 36.4% and 18.1% of the total ion deposition, whereas those in the wet gauge were NH 4 + and SO 4 2-, accounting for 32.5% and 25.0% of the total ion deposition, respectively.
Conclusion:The seasonal differences in deposition amounts of water-soluble ion species in ambient aerosol depending on the two types of different sampling methods were identified. This suggests that the removal of ambient aerosol is strongly influenced by the weather conditions of each season as well as the condition of earth's surface, such as dry ground and water.
