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Be activity concentrations in Dazaifu (western Japan)Narazaki, Yukinori*; Sakoda, Akihiro; Akata, Naofumi*; Ito, Hisanori*; Momoshima, Noriyuki*
Journal of Environmental Radioactivity, 284, p.107612_1 - 107612_10, 2025/04
Times Cited Count：1 Percentile：0.00(Environmental Sciences)Atmospheric Be activity concentration was continuously measured in Dazaifu, western Japan, from 1999 to 2020, and its variation was analyzed. Daily Be data analysis, encompassing an analysis for 22 years, revealed a concentration range of not detected - 18 mBq/m
, characterized by substantial monthly variation and smoothed annual variation. An average daily Be activity concentration of 5.0 
2.6 mBq/m was considered to be representative at the ground-surface-level in 30-40
N. Results from a two-way Analysis of variance (ANOVA) indicated statistical significance in monthly and annual Be variabilities. The monthly variability of Be activity concentration was approximately four times greater than the annual variability. Frequency analysis revealed that the monthly variability comprised major 12-month and minor 6-month periodicities. The substantial decrease in Be activity concentration during summer, a primary driver of monthly variation, was also observed at other locations in Japan, attributed to a stable high-pressure system in the Pacific Ocean that stalled over Japan's southern seas, followed by the inflow of air masses containing low Be activity concentrations. The annual variation was primarily influenced by the 11-year solar activity cycle, which affects the intensity of cosmic rays that produce Be.
Be activity concentrations with respect to precipitationNarazaki, Yukinori*; Sakoda, Akihiro; Akata, Naofumi*; Ito, Hisanori*; Momoshima, Noriyuki*
Journal of Environmental Radioactivity, 277, p.107432_1 - 107432_7, 2024/07
Times Cited Count：2 Percentile：8.23(Environmental Sciences)Beryllium-7 activity concentrations in the atmosphere and precipitation were continuously measured every day between April 2011 and December 2015 in Dazaifu, western Japan. The measured data were quantitatively analyzed to determine the precipitation-induced variation in Be activity concentrations. The average concentrations on nonprecipitation and precipitation days were 5.5 and 3.8 mBq/m, respectively. This difference of 31% (1.7 mBq/m) on average, was attributable to the washout effect, which was more significant in the summer. Regarding the association between Be activity concentration and precipitation, the concentration remained at a similar level for the small precipitation amount of 
5.0 mm/day and showed a decreasing trend (but was insignificant) for the precipitation of 5.0-10.0 mm/day. A significant decrease in the concentration was observed for 
10 mm/day. Furthermore, when precipitation occurred on two successive days, the Be activity concentrations on the second day significantly decreased regardless of precipitation.
Be activity concentrations in the atmosphereNarazaki, Yukinori*; Sakoda, Akihiro; Akata, Naofumi*; Ito, Hisanori*; Momoshima, Noriyuki*
International Journal of Environmental Research and Public Health, 19(16), p.10128_1 - 10128_9, 2022/08
Times Cited Count：5 Percentile：39.67(Environmental Sciences)In March 2013, increased Be activity concentrations in the atmosphere were observed for successive days in Dazaifu, western Japan. The daily Be activity concentration averages ranged from 0.93 to 14 mBq/m, with a monthly average of 8.3 mBq/m. This average was the highest among the monthly averages observed between 1999 and 2015 and higher than the monthly average over this period (4.7 mBq/m) plus twice the standard deviation (1.7 
2 mBq/m = 8.1 mBq/m). Also, this exceeded the monthly average (6.0 mBq/m) only for March 1999-2015, excluding 2013, where the cosmic-ray intensity, a component producing Be, decreased. Based on the backward trajectory analysis results, the inflow of air from the stratosphere and upper troposphere at high latitudes that frequently occurred in March 2013 was considered the reason for the Be activity concentration increase.
Be; Particle size distribution and chemical composition of Be-carrying aerosols in the atmosphere in JapanNarazaki, Yukinori*; Sakoda, Akihiro; Takahashi, Shunta*; Momoshima, Noriyuki*
Journal of Environmental Radioactivity, 237, p.106690_1 - 106690_7, 2021/10
Times Cited Count：10 Percentile：31.71(Environmental Sciences)The particle size distributions of airborne aerosols with Be were measured using cascade impactors at Dazaifu, a city in western Japan, in 2018 to observe their seasonal variation. Be was found to be attached to aerosols with a particle size of less than 2.1 
m; in general, particles sized 0.43-0.65 m had the highest Be activity concentrations. The activity median aerodynamic diameter (AMAD) of Be was in the range of 0.39-0.52 m, which is the size range of particles that can reach human alveoli, and had an annual mean of 0.430.035 m. The activity concentrations of Be were significantly lower in summer, which affected its activity concentrations in the particle size distributions of Be. The particle size distribution of Be-carrying aerosols was also affected by that of the aerosol particles in the atmosphere. Finally, findings suggest that Be was mainly attached to sulfate aerosols (particularly ammonium sulfate aerosols).
