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A Simulation Study on PM2.5 Sources and Meteorological Characteristics at the Northern tip of Taiwan in the Early Stage of the Asian Haze Period

Category: Observational and model studies to distinguish between locally emitted and long-range-transported

Volume: 17 | Issue: 12 | Pages: 3166-3178
DOI: 10.4209/aaqr.2017.05.0185
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Ming-Tung Chuang 1, Charles C.-K. Chou2, Neng-Huei Lin3, Akinori Takami4, Ta-Chi Hsiao5, Tang-Huang Lin6, Joshua S. Fu7, Shantanu Kumar Pani3, Yun-Ru Lu1, Tsung-Yeh Yang1

  • 1 Graduate Institute of Energy Engineering, National Central University, Taoyuan 32001, Taiwan
  • 2 Research Center for Environmental Changes, Academia Sinica, Taipei 11529, Taiwan
  • 3 Department of Atmospheric Sciences, National Central University, Taoyuan 32001, Taiwan
  • 4 Center for Regional Environmental Research, National Institute for Environmental Studies, Ibaraki 305-8506, Japan
  • 5 Graduate Institute of Environmental Engineering, National Central University, Taoyuan 32001, Taiwan
  • 6 Center for Space and Remote Sensing Research, National Central University, Taoyuan 32001, Taiwan
  • 7 Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996, USA

Highlights

First simulation study that explains the PM2.5 variation at CAFE.
It found the characteristics of three types of episodes occurred at CAFE.
High PM2.5 observed at CAFE during Asian haze period is not consistently from LRT.
Under prevailing east wind, LP in the moving northward cyclone elevate PM2.5 at CAFE.
NO3 is an important indicator of LP during the Asian haze period.


Abstract

The present study utilizes air quality modeling to probe the sources and characteristics of PM2.5 (particles less than 2.5 micrometers in aerodynamic diameter) at the northern tip of Taiwan (CAFE station) in the early stage of the Asian haze period. Since CAFE is the first place that is influenced by the Asian haze coming from the north, this study focused on the wind field, PM2.5 concentration, and PM2.5 composition at CAFE. During the research period (Oct. 16, 2015, to Nov. 15, 2015), four PM2.5 episodes occurred at CAFE. This study classified these four episodes into three types, according to their PM2.5 sources: the long-range transport (LRT) type, the local pollution (LP) type, and the LRT/LP mix type. For the LRT type, Asian outflows prevailed in a north to northeast wind at the north of Taiwan. The proportion of NO3 in the PM2.5 resolvable compositions was very small at CAFE due to evaporation during transport, whereas the relative proportion of sea salt increased due to strong winds. For the LP type, an east wind prevailed and formed a cyclone/lee vortex in northwest Taiwan. Although the background PM2.5 concentrations were low (4–20 µg m–3), the cyclone transported local anthropogenic emissions northward and elevated the PM2.5 levels at CAFE. For the LRT/LP mix type, an east wind also prevailed, but the background PM2.5 concentrations were at an intermediate level (20–30 µg m–3) because the Asian outflows had already transported haze to the West Pacific. The combined LRT and LP increased PM2.5 at CAFE. In addition, the proportions of NO3 (nitrate) for the LP and LRT/LP episodes were obviously higher than those on the days before and after. This suggests a considerable contribution on PM2.5 from LP.

Keywords

PM2.5 Asian haze Long-range transport Local pollution Modeling


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