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Kaneyasu, Naoki*; Kutsuna, Shuzo*; Iida, Kenjiro*; Sanada, Yukihisa; Tajiri, Takuya*
Environmental Science & Technology, 56(17), p.12036 - 12044, 2022/09
Times Cited Count：0 Percentile：0.00(Engineering, Environmental)Radionuclides released during the Fukushima Daiichi nuclear accident caused altitude-dependent surface contamination in the mountainous areas of Japan. To explore the possible cloudwater deposition that formed a distinctive contamination profile, data from pollen sensors deployed nationwide were analyzed. Utilizing the polarization of scattered light, Cedar pollen and water droplets were distinguished. On March 15, when surface contamination was simulated in previous studies, dense cloud with high droplet number density were observed outside the 
Cs surface deposition areas, indicating that the sensor sites were immersed amid cloud layers. In contrast, cloud droplets with moderate number density were measured at altitudes of approximately 570-840 m, which overlapped with the surface contamination areas. Considering the existing knowledge on vertical gradients of cloudwater composition, these suggest that contaminated cloud droplets were localized near the cloud base where a moderate number density of cloud droplets was measured. A formation process was proposed for the observed vertical distribution, that is, surface contamination occurred intensively at the contact line between the cloud base and mountain slopes via cloudwater deposition, and the descending cloud base formed the contamination zone. This study sheds light on the deposition processes of radionuclides which have not previously been clarified.
Sanada, Yukihisa; Katata, Genki*; Kaneyasu, Naoki*
Isotope News, (759), p.18 - 21, 2018/10
no abstracts in English
Sanada, Yukihisa; Katata, Genki*; Kaneyasu, Naoki*; Nakanishi, Chika*; Urabe, Yoshimi*; Nishizawa, Yukiyasu*
Science of the Total Environment, 618, p.881 - 890, 2018/03
Times Cited Count：23 Percentile：58.37(Environmental Sciences)Although the reconstruction of atmospheric deposition processes of radiocesium during the Fukushima Daiichi Nuclear Power Station (FDNPS) accident is essential, the whole picture of the deposition mechanism in complex topography has not been well understood yet. To understand atmospheric deposition processes of aerosols over the complex mountainous topography, we analyzed altitudinal characteristics of radiocesium released during the accident. At five selected mountainous areas in the eastern Japan, altitudinal characters of air dose rate observed by our high-resolution airborne surveys after the accident was analyzed based on the results of three typical (dry, wet, and cloud water) deposition obtained from the latest atmospheric dispersion.
Sanada, Yukihisa; Nakanishi, Chika*; Urabe, Yoshimi*; Kaneyasu, Naoki*; Katata, Genki*
no journal, ,
no abstracts in English
Tsuchiya, Nozomu*; Ikemori, Fumikazu*; Kawasaki, Kazuo*; Yamada, Rena*; Hata, Mitsuhiko*; Furuuchi, Masami*; Iwamoto, Yoko*; Kaneyasu, Naoki*; Watanabe, Takahiro; Kameda, Takayuki*; et al.
no journal, ,
It is important to assess the impact of iron oxide aerosols, e.g. from fossil fuel combustion, on climate change. However, observations of iron oxide aerosols are limited worldwide and knowledge on their behavior in the environment is insufficient. Therefore, this study attempted to elucidate the sources of combustion-derived iron oxides (coal, oil and biomass) and their seasonal variations by measuring magnetization, radiocarbon and stable carbon isotope ratios, black carbon and elemental carbon concentrations in aerosol samples collected in the Noto region, a downwind region of East Asia.
Tsuchiya, Nozomu*; Yamada, Rena*; Hata, Mitsuhiko*; Furuuchi, Masami*; Matsuki, Atsushi*; Ikemori, Fumikazu*; Kawasaki, Kazuo*; Iwamoto, Yoko*; Kaneyasu, Naoki*; Watanabe, Takahiro; et al.
no journal, ,
This study aimed to elucidate the seasonal (temporal) variation of iron oxides and their source based on the annual observation using environmental magnetic measurement at a downwind remote site in Noto. As a result, iron oxides (magnetization) showed a similar variation to black carbon (BC), but the BC-magnetization ratio increased/decreased depending on the combustion source: coal (continental), oil (domestic), biomass. This ratio can therefore be regarded as an environmental proxy to identify the combustion source.
