In this study, the mixture of mineral dust and sea salt in particles collected at southwestern Japan are reported and discussed. About 60～85% of dust particles were internally mixed with sea salt during they dispersed from China to Japan. The relative weight ratios of mineral components to sea salt in individual particles showed that the mixtures of particles were dominated by mineral, by sea salt or by both. Size distributions of the particles segregated by the mixture levels of mineral and sea salt in the three dust storm events were similar and all distributions showed a diameter range of 1～8 μm with maximum mode around 3 μm. We compared the size and composition of the particles before and after the water-soluble components in the particles were removed by water dialysis. It was found that the post-dialysis number-size distributions of mineral-sea salt mixture particles shifted toward smaller ranges compared to their pre-dialysis distributions and the more sea salt the particles contained the larger the shift of their distribution was, while the dialysis did not cause apparent changes in size or morphology of particles in which sea salt was not identified. Estimation from total detected dust particles revealed that mixing with sea salt had caused their size distributions to shift to larger ranges approximately by 0.4 ～ 0.8 μm. Based on these results, we suggest that the critical diameter for dust particle dispersion was possibly around 3 μm and a dust particle might be removed rapidly if it became larger than this scale in the marine atmosphere.
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