Volume 11, No. 5, October 2011, Pages 497-507 PDF(1.83 MB)
Aerial Observation of Aerosols Transported from East Asia — Chemical Composition of Aerosols and Layered Structure of an Air Mass over the East China Sea
Shiro Hatakeyama1, Sayuri Hanaoka1, Keisuke Ikeda1, Izumi Watanabe1, Takemitsu Arakaki2, Yasuhiro Sadanaga3, Hiroshi Bandow3, Shungo Kato4, Yoshizumi Kajii4, Kei Sato5, Atsushi Shimizu5, Akinori Takami5
1 Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
2 University of Ryukyus, Nishihara, Okinawa 903-0213, Japan
3 Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
4 Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
5 National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
Aerial observation was conducted during spring (March–April) 2008 over the East China Sea to analyze the transport of atmospheric pollutants from East Asia and the transformation processes during transport. Concentrations of sulfur dioxide (SO2), ozone (O3), total reactive nitrogen (NOy), carbon monoxide (CO), and black carbon (BC) were measured on board the aircraft, and chemical analyses of aerosols were performed subsequently by high-volume filter sampling of aerosols and ion chromatography and inductively coupled plasma-mass spectroscopy (ICP-MS) analyses. The distributions of gases and aerosols clearly suggested a layered structure to the air mass, in good agreement with predictions of the CFORS (Chemical weather FORecast System) model. The non-sea-salt (nss)-[sulfate (SO42–)]/([SO2] + nss[SO42–]) ratio value, which increased from north to south along the aircraft flight track, indicated oxidation of SO2 to form sulfuric acid during transport. In addition, pronounced chlorine loss suggested that substantial production of acidic substances occurred in the air mass as it moved away from China. The negative correlation between the Cl–/Na+ ratio and the nss–sulfate concentration suggested that the reaction of sulfuric acid with sea salt was the main cause of the strong chlorine loss. On 28 March a very clear layered structure of the air mass was observed that could be clearly explained by the CFORS computer simulation model. Therefore, here the observation results obtained on 28 March 2008 are reported.
Long-range transport; East Asia; Ionic species; Metallic components; Chlorine loss.