Chemical characterization and source identification of PM<sub>2.5</sub> at multiple sites in the Beijing–Tianjin–Hebei region, China
The simultaneous observation and analysis of atmospheric fine particles (PM<sub>2.5</sub>) on a regional scale is an important approach to develop control strategies for haze pollution. In this study, samples of filtered PM<sub>2.5</sub> were collected simultaneously at th...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/12941/2017/acp-17-12941-2017.pdf |
| Summary: | The simultaneous observation and analysis of atmospheric fine particles
(PM<sub>2.5</sub>) on a regional scale is an important approach to develop control
strategies for haze pollution. In this study, samples of filtered PM<sub>2.5</sub>
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
PM<sub>2.5</sub> 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 PM<sub>2.5</sub> source in this region, accounting for 29.2–40.5 % of
the PM<sub>2.5</sub> mass at the urban sites; the second-largest PM<sub>2.5</sub> 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 OC ∕ EC mass ratio of PM<sub>2.5</sub> 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 PM<sub>2.5</sub> 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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| ISSN: | 1680-7316 1680-7324 |