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Volume 17, issue 21 | Copyright

Special issue: Regional transport and transformation of air pollution in...

Atmos. Chem. Phys., 17, 12941-12962, 2017
https://doi.org/10.5194/acp-17-12941-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 03 Nov 2017

Research article | 03 Nov 2017

Chemical characterization and source identification of PM2.5 at multiple sites in the Beijing–Tianjin–Hebei region, China

Xiaojuan Huang1,2, Zirui Liu1,3, Jingyun Liu1, Bo Hu1, Tianxue Wen1, Guiqian Tang1, Junke Zhang1, Fangkun Wu1, Dongsheng Ji1, Lili Wang1, and Yuesi Wang1,3 Xiaojuan Huang et al.
  • 1State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
  • 2Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu, China
  • 3Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China

Abstract. The simultaneous observation and analysis of atmospheric fine particles (PM2.5) on a regional scale is an important approach to develop control strategies for haze pollution. In this study, samples of filtered PM2.5 were collected simultaneously at three urban sites (Beijing, Tianjin, and Shijiazhuang) and at a regional background site (Xinglong) in the Beijing–Tianjin–Hebei (BTH) region from June 2014 to April 2015. The PM2.5 at the four sites was mainly comprised of organic matter, secondary inorganic ions, and mineral dust. Positive matrix factorization (PMF) demonstrated that, on an annual basis, secondary inorganic aerosol was the largest PM2.5 source in this region, accounting for 29.2–40.5% of the PM2.5 mass at the urban sites; the second-largest PM2.5 source was motor vehicle exhaust, particularly in Beijing (24.9%), whereas coal combustion was also a large source in Tianjin (12.4%) and Shijiazhuang (15.5%), with particular dominance in winter. Secondary inorganic aerosol plays a vital role in the haze process, with the exception of the spring haze in Shijiazhuang and Tianjin, for which the dust source was crucial. In addition to secondary transformations, local direct emissions (coal combustion and motor vehicle exhaust) significantly contribute to the winter haze at the urban sites. Moreover, with the aggravation of haze pollution, the OCEC mass ratio of PM2.5 decreased considerably and the nitrate-rich secondary aerosol increased during all four seasons in Beijing, both of which indicate that local motor vehicle emissions significantly contribute to the severe haze episodes in Beijing. To assess the impacts of regional transport on haze pollution, the PMF results were further processed with backward-trajectory cluster analysis, revealing that haze pollution usually occurred when air masses originating from polluted industrial regions in the south prevailed and is characterized by high PM2.5 loadings with considerable contributions from secondary aerosols. This study suggests that control strategies to mitigate haze pollution in the BTH region should focus on the reduction of gaseous precursor emissions from fossil fuel combustion (motor vehicle emissions in Beijing and coal combustion in Tianjin, Hebei, and nearby provinces).

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Recently, haze pollution has frequently occurred in North China. Therefore, we conducted synchronous measurements of PM2.5 for 1 year to investigate the haze formation mechanism, sources, and influences of regional transport. The results revealed that secondary aerosols, coal combustion, and motor vehicle exhaust exerted significant impacts on urban haze formation. The mitigation strategy of reducing gaseous precursors emitted from fossil fuel combustion was suggested.
Recently, haze pollution has frequently occurred in North China. Therefore, we conducted...
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