While a further refinement of the model calculation is recommended (e.g., utilizing input meteorological data at a finer time resolution to simulate resuspensions due to short-term wind disturbances), the findings provide vital information for assessing the atmospheric 137Cs concentration in the DRZ i.e., an application of the resuspension factor (m−1) obtained from urbanized areas, where the soil particle resuspension would dominate, can result in biased estimates of the surface air 137Cs concentration. Our model’s concept illustrates that the 137Cs accumulation in fungal spores and the high spore emission characterized by the rural environment are likely responsible for the common spore 137Cs occurrence, although the former phenomenon must be experimentally validated. Alternatively, the higher 137Cs concentrations are reproduced by the fungal spore 137Cs emission that replenishes low soil particle resuspension in summer–autumn. Abstract: A processor obtains a first measurement value representing prediction performance of a model that has been learned by using a first parameter value. Our model calculation shows that the soil particle resuspension is primarily responsible for the surface air 137Cs observed during winter–spring, but could not account for the higher 137Cs concentrations observed in summer–autumn. We propose herein a model for simulating the 137Cs resuspension as soil particles and fungal spores and apply it to the DRZ to elucidate the relative importance of the two resuspension phenomena.
While wind-induced soil particle resuspension is recognized as a primary resuspension mechanism, studies following the FDNPP accident have suggested possibilities that fungal spores can be a significant source of the atmospheric 137Cs in rural areas, such as the difficult-to-return zone (DRZ), albeit the quantitative impact on the atmospheric 137Cs concentration being insufficiently understood. One of the current major radiation exposure pathways from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident-fallout is the inhalation of re-suspended 137Cs occurring in air.
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