Cosmogenic Be; Particle size distribution and chemical composition of Be-carrying aerosols in the atmosphere in Japan

宇宙線生成核種Be; 日本の大気中におけるBe付着エアロゾルの粒径分布と化学組成

楢崎 幸範*; 迫田 晃弘   ; 高橋 駿太*; 百島 則幸*

Narazaki, Yukinori*; Sakoda, Akihiro; Takahashi, Shunta*; Momoshima, Noriyuki*

2018年に西日本の太宰府市において、Beが付着したエアロゾルの粒径分布をカスケードインパクターで測定し、その季節変動を観察した。Beは粒径2.1m以下のエアロゾルに付着していることがわかり、概して0.43-0.65mの粒径で最も放射能濃度が高かった。Beの空気力学的放射能中央径(AMAD)は、ヒトの肺胞に到達可能な粒子のサイズ範囲である0.39-0.52mの範囲にあり、年平均は0.430.035mであった。Beの放射能濃度は夏季で有意に低かった。また、Beが付着したエアロゾルの粒径分布は、大気中のエアロゾル粒子の粒径分布の影響を受けていた。さらに、Beは主に硫酸塩エアロゾル(特に、硫酸アンモニウムエアロゾル)に付着していることが示唆された。

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).