2020 Volume 35 Issue 3 Pages 208-218
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.
