1.

論文(リポジトリ)

論文(リポジトリ)
Itahashi, Syuichi ; Hatakeyama, Shiro ; Shimada, Kojiro ; Takami, Akinori
出版情報: Aerosol and Air Quality Research.  19  pp.587-600,  2019-03.  Taiwan Association for Aerosol Research
URL: http://hdl.handle.net/20.500.12000/0002019366
概要: Intensive observation campaigns approximately 1 week long were conducted periodically from March 2010 to November 2015 a t Cape Hedo, Okinawa, Japan. The maximum daily mean sulfate aerosol (SO_4^<2->) concentrations surpassed 15 µg m^<–3> in spring 2012. In this study, source apportionment for these high concentrations was conducted using an air quality model with the tagged tracer method, and the main source was identified as volcanoes in March and as anthropogenic emissions from China in April. In March, the prevailing northerly wind transported a volcanic SO_2 plume with a low conversion ratio to Cape Hedo. The impacts of 15 volcanoes in Japan were estimated, and a substantial impact from Sakurajima, which accounted for more SO_2 than anthropogenic emissions from Japan, was found. Because the model had difficulty capturing the highest concentration, three sensitivity simulations were performed to consider the uncertainty of the volcanic SO_2 emission amounts and injection heights, revealing the importance of the injection height in addition to the SO_2 emission amount. Throughout April, contributions from anthropogenic emissions from China were found; hence, this source was further divided into 31 provincial scales. Shandong and Jiangsu Provinces, which are the first and seventh largest emission sources in China, respectively, were identified as significant sources at Cape Hedo. These sources showed day-to-day variation in their contributions, and the highest contribution from Shandong Province occurred on April 23, whereas that from Jiangsu Province occurred on April 22. 続きを見る
2.

論文(リポジトリ)

論文(リポジトリ)
Tatsuta, Shiori ; Shimada, Kojiro ; Chan, K. Chak ; Kim, Pyo Yong ; Lin, Neng-Huei ; Takami, Akinori ; Hatakeyama, Shiro
出版情報: Aerosol and Air Quality Research.  17  pp.3119-3127,  2017-12.  Taiwan Association for Aerosol Research
URL: http://hdl.handle.net/20.500.12000/0002019361
概要: We observed the size distributions of mass concentration, ionic composition, and trace metal concentration in aerosols c ollected at an urban site in Kumamoto Prefecture (KM) and a rural site at Cape Hedo in Okinawa Prefecture (HD) between 2012 and 2015. To evaluate the contribution of transboundary nitrate and locally emitted nitrate in the aerosols at Kumamoto, we distinguished between days of transboundary air pollution from East Asia and days of local air pollution on the basis of a threshold for Pb concentration and the ratio Pb (in 0.5 < projected area diameter (Dp) < 1.0 µm)/Cu (in 2.5 < Dp < 10 µm). Fine nitrate (particulate NH_4NO_3) did not arrive at HD from the Asian continent even under long-range transport conditions. Fine nitrate emitted in Kumamoto and its vicinity also was not transported to HD, even in an air mass that passed over KM and reached HD within one day. Almost all fine nitrate was converted to coarse nitrate during transport by dissociation of fine nitrate and adsorption of HNO_3 on larger aerosol particles. Transboundary nitrate existed largely in the particle size range of 0.5 < Dp < 10 µm, and the contribution of transboundary nitrate in the particle size range of 0.1 < Dp < 0.5 µm was about 20% even under long-range transport conditions. The contribution of transboundary nitrate in particles with Dp < 2.5 µm at KM was approximately 50%, 50%, and 80% in spring, autumn, and winter, respectively. 続きを見る
3.

論文(リポジトリ)

論文(リポジトリ)
Itahashi, Syuichi ; Hatakeyama, Shiro ; Shimada, Kojiro ; Tatsuta, Shiori ; Taniguchi, Yuta ; Chan, K. Chak ; Kim, Pyo Yong ; Lin, Neng-Huei ; Takami, Akinori
出版情報: Aerosol and Air Quality Research.  17  pp.3079-3090,  2017-12.  Taiwan Association for Aerosol Research
URL: http://hdl.handle.net/20.500.12000/0002019364
概要: An intensive observation campaign at Cape Hedo, Okinawa, Japan was conducted from late October to early November 2015 to investigate the behavior of long-range transported atmospheric pollutants. During this period, sulfate (SO_4^<2->) was the dominant aerosol component. The sources of SO_4^<2-> were estimated by using the air quality model with the tagged tracer method. The main source of high SO_4^<2-> concentration varied day-to-day. When the westerly wind was dominant (October 27), the main source was anthropogenic SO_2 emissions in China. When the northerly wind prevailed (November 1), the impact of volcanoes in western Japan was significant and the conversion ratio from SO_2 to SO_4^<2-> was lowest, at less than 70%, because of the faster transport. During the latter part of the campaign, the northerly to easterly winds were prominent, and the impacts of Korea, Japan, and ships on SO_4^<2-> observed at Cape Hedo were also clear. When the contributions from Korea, Japan, and ships were the highest (November 4), the conversion ratio was also the highest, at greater than 95% because of long-range transport. The modeled sources of volcanoes and ship emissions corresponded well with the observed coarse-mode SO_4^<2-> and V/Mn ratio, respectively. The mutual evaluation of sources from model and observations enable SO_4^<2-> sources to be estimated with higher confidence. 続きを見る