Nitrate transboundary heavy pollution over East Asia in winter

Syuichi Itahashi, Itsushi Uno, Kazuo Osada, Yusuke Kamiguchi, Shigekazu Yamamoto, Kei Tamura, Zhe Wang, Yasunori Kurosaki, Yugo Kanaya

Research output: Contribution to journalArticle

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Abstract

High PM2. 5 concentrations of around 100μgm-3 were observed twice during an intensive observation campaign in January 2015 at Fukuoka (33.52°N, 130.47°E) in western Japan. These events were analyzed comprehensively with a regional chemical transport model and synergetic ground-based observations with state-of-the-art measurement systems, which can capture the behavior of secondary inorganic aerosols (SO4 2-, NO3-, and NH4-). The first episode of high PM2. 5 concentration was dominated by NO3- (type N) and the second episode by SO4 2- (type S). The concentration of NH4- (the counterion for SO4 2- and NO3-) was high for both types. A sensitivity simulation in the chemical transport model showed that the dominant contribution was from transboundary air pollution for both types. To investigate the differences between these types further, the chemical transport model results were examined, and a backward trajectory analysis was used to provide additional information. During both types of episodes, high concentrations of NO3- were found above China, and an air mass that originated from northeast China reached Fukuoka. The travel time from the coastline of China to Fukuoka differed between types: It was 18h for type N and 24h for type S. The conversion ratio of SO2 to SO4 2- (Fs) was less than 0.1 for type N, but reached 0.3 for type S as the air mass approached Fukuoka. The higher Fs for type S was related to the higher relative humidity and the concentration of HO2, which produces H2O2, the most effective oxidant for the aqueous-phase production of SO4 2-. Analyzing the gas ratio as an indicator of the sensitivity of NO3- to changes in SO4 2- and NH4- showed that the air mass over China was NH3-rich for type N, but almost NH3-neutral for type S. Thus, although the high concentration of NO3- above China gradually decreased during transport from China to Fukuoka, higher NO3- concentrations were maintained during transport owing to the lower SO4 2- for type N. In contrast, for type S, the production of SO4 2- led to the decomposition of NH4NO3, and more SO4 2- was transported. Notably, the type N transport pattern was limited to western Japan, especially the island of Kyushu. Transboundary air pollution dominated by SO4 2- (type S) has been recognized as a major pattern of pollution over East Asia. However, our study confirms the importance of transboundary air pollution dominated by NO3-, which will help refine our understanding of transboundary heavy PM2. 5 pollution in winter over East Asia.

Original languageEnglish
Pages (from-to)3823-3843
Number of pages21
JournalAtmospheric Chemistry and Physics
Volume17
Issue number6
DOIs
Publication statusPublished - Mar 20 2017

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transboundary pollution
air mass
atmospheric pollution
nitrate
pollution
winter
oxidant
travel time
relative humidity
trajectory
decomposition
aerosol
coast
gas
simulation
chemical
Asia

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

Itahashi, S., Uno, I., Osada, K., Kamiguchi, Y., Yamamoto, S., Tamura, K., ... Kanaya, Y. (2017). Nitrate transboundary heavy pollution over East Asia in winter. Atmospheric Chemistry and Physics, 17(6), 3823-3843. https://doi.org/10.5194/acp-17-3823-2017

Nitrate transboundary heavy pollution over East Asia in winter. / Itahashi, Syuichi; Uno, Itsushi; Osada, Kazuo; Kamiguchi, Yusuke; Yamamoto, Shigekazu; Tamura, Kei; Wang, Zhe; Kurosaki, Yasunori; Kanaya, Yugo.

In: Atmospheric Chemistry and Physics, Vol. 17, No. 6, 20.03.2017, p. 3823-3843.

Research output: Contribution to journalArticle

Itahashi, S, Uno, I, Osada, K, Kamiguchi, Y, Yamamoto, S, Tamura, K, Wang, Z, Kurosaki, Y & Kanaya, Y 2017, 'Nitrate transboundary heavy pollution over East Asia in winter', Atmospheric Chemistry and Physics, vol. 17, no. 6, pp. 3823-3843. https://doi.org/10.5194/acp-17-3823-2017
Itahashi S, Uno I, Osada K, Kamiguchi Y, Yamamoto S, Tamura K et al. Nitrate transboundary heavy pollution over East Asia in winter. Atmospheric Chemistry and Physics. 2017 Mar 20;17(6):3823-3843. https://doi.org/10.5194/acp-17-3823-2017
Itahashi, Syuichi ; Uno, Itsushi ; Osada, Kazuo ; Kamiguchi, Yusuke ; Yamamoto, Shigekazu ; Tamura, Kei ; Wang, Zhe ; Kurosaki, Yasunori ; Kanaya, Yugo. / Nitrate transboundary heavy pollution over East Asia in winter. In: Atmospheric Chemistry and Physics. 2017 ; Vol. 17, No. 6. pp. 3823-3843.
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N2 - High PM2. 5 concentrations of around 100μgm-3 were observed twice during an intensive observation campaign in January 2015 at Fukuoka (33.52°N, 130.47°E) in western Japan. These events were analyzed comprehensively with a regional chemical transport model and synergetic ground-based observations with state-of-the-art measurement systems, which can capture the behavior of secondary inorganic aerosols (SO4 2-, NO3-, and NH4-). The first episode of high PM2. 5 concentration was dominated by NO3- (type N) and the second episode by SO4 2- (type S). The concentration of NH4- (the counterion for SO4 2- and NO3-) was high for both types. A sensitivity simulation in the chemical transport model showed that the dominant contribution was from transboundary air pollution for both types. To investigate the differences between these types further, the chemical transport model results were examined, and a backward trajectory analysis was used to provide additional information. During both types of episodes, high concentrations of NO3- were found above China, and an air mass that originated from northeast China reached Fukuoka. The travel time from the coastline of China to Fukuoka differed between types: It was 18h for type N and 24h for type S. The conversion ratio of SO2 to SO4 2- (Fs) was less than 0.1 for type N, but reached 0.3 for type S as the air mass approached Fukuoka. The higher Fs for type S was related to the higher relative humidity and the concentration of HO2, which produces H2O2, the most effective oxidant for the aqueous-phase production of SO4 2-. Analyzing the gas ratio as an indicator of the sensitivity of NO3- to changes in SO4 2- and NH4- showed that the air mass over China was NH3-rich for type N, but almost NH3-neutral for type S. Thus, although the high concentration of NO3- above China gradually decreased during transport from China to Fukuoka, higher NO3- concentrations were maintained during transport owing to the lower SO4 2- for type N. In contrast, for type S, the production of SO4 2- led to the decomposition of NH4NO3, and more SO4 2- was transported. Notably, the type N transport pattern was limited to western Japan, especially the island of Kyushu. Transboundary air pollution dominated by SO4 2- (type S) has been recognized as a major pattern of pollution over East Asia. However, our study confirms the importance of transboundary air pollution dominated by NO3-, which will help refine our understanding of transboundary heavy PM2. 5 pollution in winter over East Asia.

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