Size change of Asian dust particles caused by sea salt interaction: Measurements in southwestern Japan

Water dialysis was applied to remove water-soluble components in the individual Asian dust particles collected in southwestern Japan. Size and composition of the particles before and after the dialysis were compared. 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. Hence, the interaction of dust particles and sea salt is likely an important process in size and composition changes of dust particles during their long range transport, consequently affecting mass transformation and radiation transfer in the atmosphere as well as the sedimental flux of mineral dust to sea surface.