Rapid transition of aerosol optical properties and water-soluble organic aerosols in cold season in Fenwei Plain

Aodong Du; Yan Li; Jiaxing Sun; Zhiqiang Zhang; Bo You; Zhijie Li; Chun Chen; Jie Li; Yanmei Qiu; Xingang Liu; Dongsheng Ji; Wenjie Zhang; Weiqi Xu; Pingqing Fu; Yele Sun

doi:10.1016/j.scitotenv.2022.154661

Rapid transition of aerosol optical properties and water-soluble organic aerosols in cold season in Fenwei Plain

Sci Total Environ. 2022 Jul 10:829:154661. doi: 10.1016/j.scitotenv.2022.154661. Epub 2022 Mar 18.

Authors

Aodong Du¹, Yan Li¹, Jiaxing Sun¹, Zhiqiang Zhang¹, Bo You¹, Zhijie Li¹, Chun Chen¹, Jie Li², Yanmei Qiu¹, Xingang Liu³, Dongsheng Ji², Wenjie Zhang⁴, Weiqi Xu², Pingqing Fu⁵, Yele Sun⁶

Affiliations

¹ State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
² State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
³ School of Environment, Beijing Normal University, Beijing 100875, China.
⁴ State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
⁵ Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China.
⁶ State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China; Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China. Electronic address: sunyele@mail.iap.ac.cn.

PMID: 35314216
DOI: 10.1016/j.scitotenv.2022.154661

Abstract

The Fenwei Plain (FWP) continues to be one of the most polluted regions in China despite the improvement of air quality in recent years. However, our understanding of aerosol optical properties (AOP) and its relationship with aerosol composition particularly in cold season is far from complete. Here we conducted three-month measurements of AOP from November 2020 to January 2021 in the FWP along with fine particle composition and water-soluble organic aerosol (WSOA) measurements. Our results showed rapid transitions in AOP from November to January due to the enhanced primary emissions and the decreased aqueous-phase processing. The single scattering albedo (SSA) decreased from 0.85 to 0.78, while the absorption Ångstrӧm exponent (AAE) increased from 1.41 to 1.60, demonstrating the increasing role of absorbing aerosol and brown carbon in cold season. Further analysis showed that SSA increased significantly with the fraction of secondary inorganic aerosol, while AAE was highly correlated with the fraction of primary OA (POA), highlighting the different impacts of primary and secondary aerosol on AOP. Chemical apportionment showed the dominant contributions of ammonium nitrate (29%) and ammonium sulfate (27%) to particle extinction before heating season, while that of POA increased to 27% during heating season. Although the pollution level showed a clear increase during the heating season, the changes in visibility were small due to the decreased mass extinction efficiency from 3.48 to 2.91 m² g^-1. Positive matrix factorization illustrated a clear transition in WSOA composition from the dominance of secondary OA (SOA) in November to POA in heating season. Compared with the large decrease in water-soluble aqueous-phase SOA, the consistently high concentration of photochemical-related SOA elucidated the presence of strong photochemical processing in cold season. Overall, our results demonstrate the significant transition in primary emissions and secondary formation in cold season, and such changes have affected AOP substantially.

Keywords: Aerosol optical properties; Fenwei Plain; Primary emissions; Secondary formation; Water-soluble organic aerosol.

MeSH terms

Aerosols / analysis
Air Pollutants* / analysis
Environmental Monitoring
Particulate Matter* / analysis
Seasons
Water / analysis

Substances

Aerosols
Air Pollutants
Particulate Matter
Water