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In oder to understand the deposition possibility of water-soluble inorganic ions in the atmospheric fine particulates for the human respiratory tract, the mass size distribution of ion species was measured using an Andersen sampler in the Iksan during fall, 2004. Samples were analyzed for major water-soluble ions using Dionex DX-100 ion chromatograph. The size distribution of water-soluble inorganic ions in the atmospheric particulates appeared bimodal distribution, which were divided around 1-2 μm into two groups. Mass size distribution of total ion in the coarse mode was found to be almost similar level during the sampling period, but fluctuations of mass size distribution in the fine mode were observed. Considering the mass size distribution of total ion concentrations for the respiratory deposition region, it was found that about 77.1% of total ions could be deposited in the alveolar region, and which dominated the daily variation of total ion concentrations. The concentration of total ions, which could be deposited in both the head region and the tracheobronchial region, was 3.95 μg/㎥, whereas that in the alveolar region was 13.28 μg/㎥. Dominant ions which could be deposited in the alveolar region were NO₃^-, SO4^(2-) and NH₄^ +, accounting for about 40%, 27% and 22% of the total ions, respectively. Although K^+ was approximately 3% of total ions, it was shown that most of this could be deposited in the alveolar region due to its high fraction of small size distribution originated from anthropogenic source of biomass burning. The presence of these ions in the fine mode may be of public health significance as they are very biologically harmful to health and have a high probability of being deposited in human lung tissue.
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