A scanning electron microscope and an energy dispersive X-ray spectrometer were applied to analyze the particles collected during dust-storm events at southwestern Japan in spring 2000. Particle morphology and elemental composition were investigated and the weight ratios of different elements in individual particles were obtained. The results indicated that, besides the coagulation of sea-salt and dust particles, chlorine could deposit onto dust particles through the absorption of chlorine-containing gases when the particles passed through the marine atmosphere between China and Japan. The quantitative estimation revealed that the chlorine deposition on many particles was not negligible compared to sulfur deposition, suggesting that dust particles could remarkably modify the chlorine chemistry in marine atmosphere and possibly vise versa. ¿ 2001 American Geophysical Union