[A-AS09] 大気化学

[AAS09-12] Seasonal change of aerosol cycles in the Akiyoshi-do Cave

*原 圭一郎¹、岩田 康平¹、田中 さや¹、田中 響¹、牧 輝弥²、石原 与四郎¹ (1.福岡大学理学部、2.近畿大学理工学部)

キーワード：エアロゾル、洞窟、霧、吸湿特性

Aerosol cycles and aerosol distributions in cave atmospheres must be investigated to elucidate the natural circumstances and to maintain public-health protection for cave sightseeing visitors. Detailed investigations measuring aerosols have not been reported for representative Japanese caves such as the Akiyoshi-do Cave, Japan. This study compared the aerosol size distributions of ambient and dry conditions, strongly suggesting remarkable hygroscopic growth and efficient dry deposition of coarse aerosol particles in the cave year-round under high relative humidity. Additionally, fog formation and dry/wet deposition of aerosol particles in the cave were observed to a considerable degree during summer and occasionally during transitional seasons. Individual particle analysis of aerosols collected outside and inside the cave revealed that the external air was transported, passing into the cave during winter and transitional seasons by ventilation effects. Aerosol particles containing water-soluble constituents were converted to fog particles during summer and the transitional seasons. Aerosol particles containing Ca (likely CaCO₃ particles) were observed in the cave atmosphere, irrespective of fog appearance during summer. Presumably, the outside aerosol particles are mixed with the cave-terrestrial particles released into the cave atmosphere. Some particles were deposited by fog, which formed because of the high humidity.