Preprints
https://doi.org/10.5194/acp-2021-637
https://doi.org/10.5194/acp-2021-637

  18 Aug 2021

18 Aug 2021

Review status: this preprint is currently under review for the journal ACP.

Measurement report: Long-term changes in black carbon and aerosol optical properties from 2012 to 2020 in Beijing, China

Jiaxing Sun1,2, Zhe Wang1, Wei Zhou1, Conghui Xie1,2,a, Cheng Wu3, Chun Chen1,2, Tingting Han1,b, Qingqing Wang1, Zhijie Li1,2, Jie Li1, Pingqing Fu4, Zifa Wang1,2,5, and Yele Sun1,2,5 Jiaxing Sun et al.
  • 1State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 2College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
  • 3Institute of Mass Spectrometer and Atmospheric Environment, Jinan University, Guangzhou 510632, China
  • 4Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China
  • 5Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
  • anow at: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
  • bnow at: Environmental Meteorology Forecast Center of Beijing-Tianjin-Hebei, Beijing 100089, China

Abstract. Atmospheric aerosols play an important role in radiation balance of the earth-atmosphere system. However, our knowledge of the long-term changes in black carbon (BC) and aerosol optical properties in China are very limited. Here we analyze the nine-year measurements of BC and aerosol optical properties from 2012 to 2020 in Beijing, China. Our results showed large reductions in eBC by 67 % from 5.54 ± 5.25 µg m−3 in 2012 to 1.80 ± 1.54 µg m−3 in 2020, and 47 % decreases in light extinction coefficient (bext, λ = 630 nm) of fine particles due to clean air action plan since 2013. The seasonal and diurnal variations of eBC illustrated the most significant reductions in the fall and night time, respectively. ΔeBC/ΔCO also showed an annual decrease from ~6 to 4 ng m−3 ppbv−1 and presented strong seasonal variations with high values in spring and fall, indicating that primary emissions in Beijing have changed significantly. As a response to clean air action, single scattering albedo (SSA) showed a considerable increase from 0.79 ± 0.11 to 0.88 ± 0.06, and mass extinction efficiency (MEE) increased from 3.2 to 3.8 m2 g−1. These results highlight an increasing importance of scattering aerosols in radiative forcing, and a future challenge in visibility improvement due to enhanced MEE. Brown carbon (BrC) showed similar changes and seasonal variations to eBC during 2018–2020. However, we found a large increase of secondary BrC in the total BrC in most seasons, particularly in summer with the contribution up to 50 %, demonstrating an enhanced role of secondary formation in BrC in recent years. The long-term changes in eBC and BrC have also affected the radiative forcing effect. The direct radiative forcing (ΔFR) of BC decreased by 64 % from +3.00 W m−2 in 2012 to +1.09 W m−2 in 2020, and that of BrC decreased from +0.30 to +0.17 W m−2 during 2018–2020. Such changes might have important implications in affecting aerosol and boundary-layer interactions and the future air quality improvement.

Jiaxing Sun et al.

Status: open (until 29 Sep 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review', Anonymous Referee #1, 07 Sep 2021 reply
  • RC2: 'Comment on acp-2021-637', Anonymous Referee #2, 09 Sep 2021 reply

Jiaxing Sun et al.

Jiaxing Sun et al.

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Short summary
We analyzed nine-year measurements of BC and aerosol optical properties from 2012 to 2020 in Beijing, China. Our results showed large reductions in BC and light extinction coefficient due to clean air action plan. As a response, both SSA and mass extinction efficiency (MEE) showed considerable increases demonstrating a future challenge in visibility improvement. The primary and secondary BrC were also separated and quantified, and the changes in redditive forcing of BC and BrC were estimated.
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