Preprints
https://doi.org/10.5194/acp-2021-947
https://doi.org/10.5194/acp-2021-947
 
01 Dec 2021
01 Dec 2021
Status: a revised version of this preprint is currently under review for the journal ACP.

Measurement report: The importance of biomass burning in light extinction and direct radiative effect of urban aerosol during the COVID-19 lockdown in China

Jie Tian1,2, Qiyuan Wang1,2,3, Huikun Liu1, Yongyong Ma4, Suixin Liu1,2, Yong Zhang1, Weikang Ran1, Yongming Han1,2,3, and Junji Cao5 Jie Tian et al.
  • 1State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
  • 2CAS Center for Excellence in Quaternary Science and Global Change, Xi’an 710061, China
  • 3Guanzhong Plain Ecological Environment Change and Comprehensive Treatment National Observation and Research Station, Xi’an 710061, China
  • 4Meteorological Institute of Shaanxi Province, Xi’an 710015, China
  • 5Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China

Abstract. To mitigate climate change in China, a better understanding of optical properties of aerosol is required due to the complexity in emission sources. Here, an intensive real-time measurement was conducted in an urban area of China before and during the lockdown of Coronavirus Disease 2019 (COVID-19), to explore the impacts of anthropogenic activities on aerosol light extinction and direct radiative effect (DRE). The mean light extinction coefficient (bext) reduced from 774.7 ± 298.1 Mm−1 during the normal period to 544.3 ± 179.4 Mm−1 during the lockdown period. The generalized addictive model analysis indicated that the large decline of bext (29.7 %) was entirely attributed to the sharp reductions in anthropogenic emissions. Chemical calculation of bext based on the ridge regression analysis showed that organic aerosol (OA) was the largest contributor to bext in both periods (45.1–61.4 %), and contributions of two oxygenated OAs to bext increased by 3.0–14.6 % during the lockdown. A hybrid environmental receptor model combining with chemical and optical variables identified six sources of bext. It was found that bext from traffic-related emission, coal combustion, fugitive dust, nitrate plus secondary OA (SOA) source, and sulfate plus SOA source decreased by 21.4–97.9 % in the lockdown, whereas bext from biomass burning increased by 27.1 % mainly driven by undiminished needs of residential cooking and heating. The atmospheric radiative transfer model was further used to illustrate that biomass burning instead of traffic-related emission 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 implied the importance of biomass burning for tackling climate change in China in the future.

Jie Tian et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on acp-2021-947', Shaofei Kong, 07 Dec 2021
  • RC1: 'Comment on acp-2021-947', Tiantao Cheng, 09 Dec 2021
  • RC2: 'Comment on acp-2021-947', Anonymous Referee #2, 26 Dec 2021
  • AC1: 'Comment on acp-2021-947', J. Tian, 09 Feb 2022

Jie Tian et al.

Data sets

Measurement report: The importance of biomass burning in light extinction and direct radiative effect of urban aerosol during the COVID-19 lockdown in China [Data set] Tian, Jie, Wang, Qiyuan, Liu, Huikun, Ma, Yongyong, Liu, Suixin, Zhang, Yong, Ran, Weikang, Han, Yongming, & Cao, Junji https://doi.org/10.5281/zenodo.5739349

Jie Tian et al.

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Short summary
We investigated aerosol optical properties and direct radiative effect (DRE) at an urban site in China before and during the Coronavirus Disease 2019 lockdown. The total light extinction coefficient (bext) reduced under emission control measures, however, bext from biomass burning increased due to the undiminished needs of residential cooking and heating. Biomass burning became the largest positive effect contributor to aerosol DRE in the lockdown instead of traffic-related emission.
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