Transport of anthropogenic aerosols from Asia and subsequent chemical transformation

Abstract

[1] Aerosol chemical composition and gaseous species were measured at Cape Hedo, Okinawa, Japan (CHO), during the ABC/EAREX project period in March 2005, using high-time-resolution instruments including an Aerodyne quadrupole aerosol mass spectrometer (Q-AMS), a tapered element oscillating microbalance (TEOM), and gas monitors in order to investigate the transport and subsequent chemical transformation of aerosol in the east Asian region. Sulfate was the dominant species in fine aerosol mode and the average concentration of ammonium, sulfate and organics was 1.25, 6.37 and 2.16 mg m À3 , respectively. The sulfate concentration observed at CHO in 2005 was about 1.5-2 times higher than that in 1994. For the majority of high-sulfate observations, the air mass was transported from the central east Chinese region (between Shanghai and the Shandong Peninsula). Sulfate transport was intermittent and strongly correlated with the passage of synoptic-scale high-/low-pressure systems. Chemical components and their concentration showed significant change on 17-18 March, which is accounted for by the change in air mass origin and the synoptic-scale weather system. In addition, it is suggested that the difference of air quality at the air mass origin reflects the chemical composition at CHO. The high sulfate concentration required heterogeneous conversion of SO 2 to sulfate at a rate of 2.0% h À1 . A pronounced signal at m/z = 44 confirmed that organic compounds were oxidized.

Impact of Asian dust and continental pollutants on cloud chemistry observed in northern Taiwan during the experimental period of ABC/EAREX 2005

“…However, variability in the range of pollutants observed at other stations in downwind areas show the regional extent of the Case C [Sawa et al, 2007;Takami et al, 2007]. Therefore, in this section, we reconsider the results from sections 3.2.1-3.2.3, along with data reported in other EAREX 2005 studies, to illustrate the regional impact of Case C in these downwind areas.…”

“…The estimated residence time for SO 2 is less than 50 h in this region in the boundary layer [Galloway, 1990], and the heterogeneous conversion rate of SO 2 to sulfate is 2.0% h −1 [Takami et al, 2007]. In this case, air pollutants spent a relatively long time aloft and were well oxidized [Takami et al, 2007]. The oxidized particle composite augments a preexiting dust core with a coating of organics, sulfate and nitrates [Haywood and Boucher, 2000].…”

“…The five continental outflow periods are, thus, classified as: Case A: 0400 UTC 2 March to 1200 UTC 4 March; Case B: 0700 UTC 11 March to 2100 UTC 13 March; Case C: 1900 UTC 17 March to 0400 UTC 19 March; Case D: 0000 UTC 23 March to 0900 UTC 25 March; Case E: 1300 UTC 28 March to 1700 UTC 30 March. Identification of these outflow cases corresponds with those of previous studies [Lee et al, 2007;Sawa et al, 2007;Takami et al, 2007].…”

“…We investigate a dust storm event that noticeably influenced air quality and cloud composition over northern Taiwan. This dust storm event was connected with a synoptic-scale weather system that developed during EAREX 2005 [Lee et al, 2007;Sawa et al, 2007;Takami et al, 2007;Choi et al, 2008]. Lidar and cloud chemistry measurements in northern Taiwan serve as ancillary data sets to help characterize the dust event.…”

Continuous Observation of the Mass and Chemical Composition of PM2.5 using an Automatic Analyzer in Kumamoto, Japan

“…This pollution was suspected to be partly due to air pollution traveling from the Asian continent owing to the seasonal monsoons. To investigate the origin of air pollution in the Kyushu region, many studies have been performed using various methods (Takami et al, 2005(Takami et al, , 2007Kaneyasu et al, 2010;Takami et al, 2013). Kaneyasu et al (2010) investigated the air mass including high concentrations of PM 2.5 originating on the Asian continent through observation at Fukuoka and Fukue Island, Japan, and Jeju Island, Korea (Kaneyasu et al, 2010).…”