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Observed and Modeled Mass Concentrations of Organic Aerosols and PM2.5 at Three Remote Sites around the East China Sea: Roles of Chemical Aging

Category: Aerosol and Atmospheric Chemistry

Article In Press
DOI: 10.4209/aaqr.2016.12.0573
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Yugo Kanaya 1, Hitoshi Matsui1,2,3, Fumikazu Taketani1, Xiaole Pan1,4,5, Yuichi Komazaki1, Zifa Wang4, Limseok Chang6, Daeil Kang6, Minhyeok Choi6, Sung-Yong Kim6, Chang-Hee Kang7, Akinori Takami8, Hiroshi Tanimoto8, Kohei Ikeda8, Kazuyo Yamaji9

  • 1 Japan Agency for Marine-Earth Science and Technology, Yokohama, Kanagawa 236-0001, Japan
  • 2 Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan
  • 3 Cornell University, Ithaca, NY 14853, USA
  • 4 Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 5 Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 819-0395, Japan
  • 6 National Institute of Environmental Research, Incheon 22689, Korea
  • 7 Jeju National University, Jeju 63243, Korea
  • 8 National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
  • 9 Kobe University, Kobe, Hyogo Prefecture 657-0013, Japan

Highlights

PM2.5 and its components were observed at three remote sites around the East China Sea.
With chemical aging, WRF-Chem model better reproduced the observed levels of organics.
High OH concentrations promoted secondary formation of organics with the VBS scheme.
Unaccounted sources of organic aerosols were implied besides the represented processes.
The model better reproduced the total PM2.5 levels when chemical aging was introduced.


Abstract

Severe PM2.5 air pollution over the Asian continent is occasionally transported across the East China Sea by the westerly winds to Japan, continuing for long distances over the Pacific Ocean. Despite such polluted air masses causing health issues, conventional models tend to underestimate levels of organic aerosols (OA) and PM2.5. Here, PM2.5 and its major components recorded during three field campaigns carried out at Fukue Island (32.75°N, 128.68°E), Japan (spring 2009), Rudong (32.25°N, 121.37°E), China (spring 2010), and Jeju (33.35°N, 126.39°E), Korea (autumn 2012) around the East China Sea were used to test the performance of the Weather Research and Forecasting-Chem/ATRAS-MOSAIC model. Overall, model performance was improved by introducing chemical aging represented by a volatility basis-set scheme, whereby median values of the model/observation ratio for OA were raised to 0.34–1.28 from 0.30–0.35 in the case of conventional settings. In particular, the levels of OA at the Fukue site and daytime buildup of the OA levels at all three sites were reproduced by the model. OA levels were still sometimes underestimated. This suggests that either emission rates of organic precursors are being underestimated or other pathways of OA formation are also important. Our analysis also indicates that this region is characterized by high OH concentrations, promoting chemical aging. The predictions of PM2.5 levels in the model also improved, with median values of the model/observation ratio shifting from 0.67–0.91 to 0.68–0.95, when chemical aging of OA was taken into account.

Keywords

Chemical transport model Regional-scale air pollution Organics Volatility basis-set scheme Oxidative capacity


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