Exploring wintertime regional haze in northeast China: role of coal and biomass burning
<p>As one of the intense anthropogenic emission regions across the relatively high-latitude (<span class="inline-formula">>40</span><span class="inline-formula"><sup>∘</sup></span> N) areas on Earth, northeast China face...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/20/5355/2020/acp-20-5355-2020.pdf |
| Summary: | <p>As one of the intense anthropogenic emission regions across the relatively
high-latitude (<span class="inline-formula">>40</span><span class="inline-formula"><sup>∘</sup></span> N) areas on Earth, northeast
China faces the serious problem of regional haze during the heating period of
the year. Aerosols in polluted haze in northeast China are poorly
understood compared with the haze in other regions of China such as the North
China Plain. Here, we integrated bulk chemical measurements with single-particle analysis from transmission electron microscopy (TEM), nanoscale
secondary ion mass spectrometry (NanoSIMS), and atomic force microscopy
(AFM) to obtain morphology, size, composition, aging process, and sources of
aerosol particles collected during two contrasting regional haze events
(Haze-I and Haze-II) at an urban site and a mountain site in northeast
China and further investigated the causes of regional haze formation.
Haze-I evolved from moderate (average <span class="inline-formula">PM<sub>2.5</sub></span>: 76–108 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>) to
heavy pollution (151–154 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>), with the dominant <span class="inline-formula">PM<sub>2.5</sub></span>
component changing from organic matter (OM) (39–45 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>) to
secondary inorganic ions (94–101 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>). Similarly, TEM
observations showed that S-rich particles internally mixed with OM (named S-OM)
increased from 29 % to 60 % by number at an urban site and 64 %
to 74 % at a mountain site from the moderate Haze-I to heavy Haze-I events,
and 75 %–96 % of Haze-I particles included primary OM. We found that change
of wind direction caused Haze-I to rapidly turn into Haze-II (185–223 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>) with predominantly OM (98–133 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>) and
unexpectedly high <span class="inline-formula">K<sup>+</sup></span> (3.8 <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>). TEM also showed that K-rich particles
internally mixed with OM (named K-OM) increased from 4 %–5 % by
number to 50 %–52 %. The results indicate that there were different sources
of aerosol particles causing the Haze-I and Haze-II formation: Haze-I was
mainly induced by accumulation of primary OM emitted from residential coal
burning and further deteriorated by secondary aerosol formation via
heterogeneous reactions; Haze-II was caused by long-range transport of
agricultural biomass burning emissions. Moreover, abundant primary OM
particles emitted from coal and biomass burning were considered to be one
typical brown carbon, i.e., tar balls. Our study highlights that large
numbers of light-absorbing tar balls significantly contribute to winter haze
formation in northeast China and they should be further considered in
climate models.</p> |
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| ISSN: | 1680-7316 1680-7324 |