冷温帯林におけるエアロゾル動態および樹木への沈着・洗浄除去状態の把握

Aerosol deposition and the behavior of aerosol particles deposited on the foliar surface of trees in cool-temperate forests in Hokkaido

渡邊 陽子*; 山口 高志*; 堅田 元喜

Watanabe, Yoko*; Yamaguchi, Takashi*; Katata, Genki

本研究では、北海道の森林樹木に対するエアロゾルの影響を解明するために、北海道東部のエアロゾル濃度と霧の化学的・物理的性質を分析した。樹木の生育期間中は、大気中エアロゾルは硫酸塩やアンモニウムイオンの濃度が最も高かった。これらのイオンは霧の主成分であった。霧の粒径は他地域より大きく、この地域の霧の沈着速度は大きくなることが示唆された。樹木の葉には、おもに土壌粒子やSを含む粒子やNaClが観察された。洗浄実験から、これらの粒子は降雨により葉表面から洗浄されることが明らかとなった。

The concentrations of atmospheric aerosols were measured by filter pack method from spring to autumn in eastern Hokkaido. Furthermore, the components of fog water collected by an active string fog collector and the diameter of fog droplets by fog monitor were analyzed in the same area. The concentrations of SO and NH in aerosols were highest during the growing period of forest trees in eastern Hokkaido. Mean diameter of fog droplets was larger than that in other areas. This suggests that fog deposition velocity would increase in this area. On the other hand, the shape and components of aerosols deposited on the surfaces of leaves of white birch trees were observed by SEM-EDX. Soil particles and particles including S, and NaCl particles were found. Washing treatment of the leaf surfaces of white birch showed that many particles deposited on the leaf surface are possible to be washed with raindrops.