Measurement report: The importance of biomass burning in light extinction and direct radiative effect of urban aerosol during the COVID-19 lockdown in Xi'an, China
<p>Due to the complexity of emission sources, a better understanding of aerosol optical properties is required to mitigate climate change in China. Here, an intensive real-time measurement campaign was conducted in an urban area of China before and during the COVID-19 lockdown in order to expl...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/8369/2022/acp-22-8369-2022.pdf |
| Summary: | <p>Due to the complexity of emission sources, a better
understanding of aerosol optical properties is required to mitigate climate
change in China. Here, an intensive real-time measurement campaign was conducted in
an urban area of China before and during the COVID-19 lockdown in order to explore the impacts of anthropogenic activities on
aerosol light extinction and the direct radiative effect (DRE). The mean light
extinction coefficient (<span class="inline-formula"><i>b</i><sub>ext</sub></span>) decreased from 774.7 <span class="inline-formula">±</span> 298.1 Mm<span class="inline-formula"><sup>−1</sup></span>
during the normal period to 544.3 <span class="inline-formula">±</span> 179.4 Mm<span class="inline-formula"><sup>−1</sup></span> during the
lockdown period. A generalised additive model analysis indicated that the
large decline in <span class="inline-formula"><i>b</i><sub>ext</sub></span> (29.7 %) was due to sharp reductions
in anthropogenic emissions. Chemical calculation of <span class="inline-formula"><i>b</i><sub>ext</sub></span> based on a
ridge regression analysis showed that organic aerosol (OA) was the largest
contributor to <span class="inline-formula"><i>b</i><sub>ext</sub></span> in both periods (45.1 %–61.4 %), and the contributions
of two oxygenated OAs to <span class="inline-formula"><i>b</i><sub>ext</sub></span> increased by 3.0 %–14.6 % during the
lockdown. A hybrid environmental receptor model combined with chemical and
optical variables identified six sources of <span class="inline-formula"><i>b</i><sub>ext</sub></span>. It was found that
<span class="inline-formula"><i>b</i><sub>ext</sub></span> from traffic-related emissions, coal combustion, fugitive dust, the
nitrate and secondary OA (SOA) source, and the sulfate and SOA source
decreased by 21.4 %–97.9 % in the lockdown, whereas <span class="inline-formula"><i>b</i><sub>ext</sub></span> from biomass
burning increased by 27.1 %, mainly driven by the undiminished need for
residential cooking and heating. An atmospheric radiative transfer model
was further used to illustrate that biomass burning, rather than
traffic-related emissions, became the largest positive effect (10.0 <span class="inline-formula">±</span> 10.9 W m<span class="inline-formula"><sup>−2</sup></span>) on aerosol DRE in the atmosphere during the lockdown. Our
study provides insights into aerosol <span class="inline-formula"><i>b</i><sub>ext</sub></span> and DRE from anthropogenic
sources, and the results imply the importance of controlling biomass
burning for tackling climate change in China in the future.</p> |
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| ISSN: | 1680-7316 1680-7324 |