Recent manufacturing processes for high performance crystal particles require the advanced control technologies of crystal structure and morphology. In order to positively control nucleation and crystal growth, it is important to understand the crystallization behavior in the solution from a microscopic viewpoint. We have studied the crystallization behavior of aqueous micro-droplet of potassium iodide (KI) solution using electrodynamic balance (EDB), where a charged droplet could be electrically levitated in space over the periods of hours. It enabled us in situ observation of crystallization behavior in a levitated micro-droplet with enough spatial and time resolutions. In this study, we investigated the final morphology and the crystallization behavior of the produced particle from evaporation of single levitated microdroplet of aqueous KI solution using EDB coupled with optical microscope. IDG (Ink-jet Droplet Generator) or DPI (Direct Particle Injection) method was adopted for trapping the droplet in EDB. The morphologies of produced crystal particle depended on the initial droplet diameter. Multilayer crystal particle was obtained from crystallization of the large droplet (80–140 μm) and the cuboid crystal with lack of one edge was observed for the small droplet (20–40 μm). We also observed the multi-crystalline particle with cascade structure of cuboid crystals or the irregular spherical particle with shell-like structure which was produced from the small droplet with high supersaturation in the case of IDG trapping method.

　Following the Fukushima Daiichi nuclear power plant accident, it has been recognized that bioaerosols with radioactive cesium may have released from radiologically contaminated forest into the atmosphere. In order to evaluate the above process, the emission rate of bioaerosol was inversely estimated using a numerical model named SOLVEG that includes the processes of emission, deposition, and turbulent transport of aerosols. For the inverse estimation, micrometeorological variables and bioaerosol number concentration and flux were observed at a Japanese temperate broad-leaved forest in summer. By tuning modelled emission rate of bioaerosols from forest floor, its best estimate was obtained at the agreement between calculated and observed concentrations below the canopy. General trends of calculated momentum, heat, and bioaerosol fluxes above the canopy were also reproduced in the simulation. In the numerical experiment without bioaerosol input at the top of atmosphere above the canopy, a certain amount (59%) of bioaerosol flux at the floor released above the canopy top, while the rest of the flux deposited onto both canopy and soil. This potential flux above the canopy top was 2.0±1.8×10^-2 μg m^-2 s^-1, which may correspond to the re-emission rate proposed previously by the chemical transport model.