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
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Published:2022-06-29
Issue:12
Volume:22
Page:8369-8384
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ISSN:1680-7324
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Container-title:Atmospheric Chemistry and Physics
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language:en
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Short-container-title:Atmos. Chem. Phys.
Author:
Tian Jie, Wang Qiyuan, Liu Huikun, Ma Yongyong, Liu Suixin, Zhang Yong, Ran Weikang, Han YongmingORCID, Cao Junji
Abstract
Abstract. 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 (bext) decreased from 774.7 ± 298.1 Mm−1
during the normal period to 544.3 ± 179.4 Mm−1 during the
lockdown period. A generalised additive model analysis indicated that the
large decline in bext (29.7 %) was due to sharp reductions
in anthropogenic emissions. Chemical calculation of bext based on a
ridge regression analysis showed that organic aerosol (OA) was the largest
contributor to bext in both periods (45.1 %–61.4 %), and the contributions
of two oxygenated OAs to bext increased by 3.0 %–14.6 % during the
lockdown. A hybrid environmental receptor model combined with chemical and
optical variables identified six sources of bext. It was found that
bext 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 bext 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 ± 10.9 W m−2) on aerosol DRE in the atmosphere during the lockdown. Our
study provides insights into aerosol bext and DRE from anthropogenic
sources, and the results imply the importance of controlling biomass
burning for tackling climate change in China in the future.
Funder
Youth Innovation Promotion Association of the Chinese Academy of Sciences West Light Foundation of the Chinese Academy of Sciences Chinese Academy of Sciences Key Research and Development Projects of Shaanxi Province
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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