Characteristics, primary sources and secondary formation of water-soluble organic aerosols in downtown Beijing
<p>Water-soluble organic carbon (WSOC) accounts for a large proportion of aerosols and plays a critical role in various atmospheric chemical processes. In order to investigate the primary sources and secondary production of WSOC in downtown Beijing, day and night fine particulate matter (PM<...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/21/1775/2021/acp-21-1775-2021.pdf |
| Summary: | <p>Water-soluble organic carbon (WSOC) accounts for a
large proportion of aerosols and plays a critical role in various atmospheric
chemical processes. In order to investigate the primary sources and
secondary production of WSOC in downtown Beijing, day and night
fine particulate matter (PM<span class="inline-formula"><sub>2.5</sub></span>) samples in January (winter), April (spring), July (summer) and
October (autumn) 2017 were collected and analyzed for WSOC and organic
tracers in this study. WSOC was dominated by its moderately hydrophilic
fraction and showed the highest concentration in January and comparable
levels in April, July and October 2017. Some typical organic tracers were
chosen to evaluate the emission strength and secondary formation of WSOC.
Seasonal variation of the organic tracers suggested significantly enhanced
formation of anthropogenic secondary organic aerosols (SOAs) during the
sampling period in winter and obviously elevated biogenic SOA formation
during the sampling period in summer. These organic tracers were applied
into a positive matrix factorization (PMF) model to calculate the source
contributions of WSOC as well as its moderately and strongly hydrophilic
portions. The secondary sources contributed more than 50 % to WSOC, with
higher contributions during the sampling periods in summer (75.1 %) and
winter (67.4 %), and the largest contributor was aromatic SOC. In addition,
source apportionment results under different pollution levels suggested that
controlling biomass burning and aromatic precursors would be effective to
reduce WSOC during the haze episodes in cold seasons. The impact factors for
the formation of different SOA tracers and total secondary organic carbon (SOC)
as well as moderately and strongly hydrophilic SOC were also investigated.
The acid-catalyzed heterogeneous or aqueous-phase oxidation appeared to
dominate in the SOC formation during the sampling period in winter, while
the photochemical oxidation played a more critical role during the sampling
period in summer. Moreover, photooxidation played a more critical role in
the formation of moderately hydrophilic SOC, while the heterogeneous or
aqueous-phase reactions had more vital effects on the formation of
strongly hydrophilic SOC.</p> |
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| ISSN: | 1680-7316 1680-7324 |