[A-AS11] Atmospheric Chemistry

[AAS11-05] Observation of plume of Nishinoshima volcano eruption on August 2020 at Okinawa and Nagasaki, Japan

*Tomoki Nakayama¹, Ryo Harada¹, Takuma Maeda^1,2, Takemitsu Arakaki³, Hiroyuki Yamada³, Fumikazu Ikemori⁴, Kazuhisa Tsuboki⁵ (1.Nagasaki Univ., 2.NPIERPH, 3.Unv. Ryukyus, 4.NCIES, 5.Nagoya Univ.)

Keywords:Aerosol, Sulfuric acid, Ammonia (NH3), Sulfur dioxide (SO2), Volcanic ash, PM2.5

Eruptions of volcano lead to input of a large amount of ash and gaseous compounds including sulfur dioxide (SO₂) to the atmosphere and contribute to radiation balance and atmospheric chemical processes. During transportation of the plume, size distributions of aerosol particles can be changed due to deposition of particles and secondary formation of sulfate particles. From the end of 2019 to 2020, explosive eruptions of Nishinosima volcano (27.247°N, 140.874°E) were reported. In this work, plumes of the volcanic eruption of Nishinoshima were observed in August of 2020 at University of the Ryukyus (26.250°N, 127.767°E, 1306 km west from Nishinoshima) in Okinawa island and at Nagasaki University (32.786°N, 129.865°E, 1225 km northwest from Nishinoshima) in western Japan. Particle size distributions were monitored by optical particle sizers at both sites and a scanning mobility particle sizer at Nagasaki University. Offline chemical analyses of aerosol particles were also conducted. In addition, gaseous ammonia (NH₃) were also monitored using a cavity ring-down spectrometer at Nagasaki University. As results, significant fractions of submicron particles were found in the plumes and acidities of the particles were enhanced, likely due to formation and transportation of sulfuric acid particles under limited amounts of available NH₃ for neutralization of particles.