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Volume 17, issue 24 | Copyright
Atmos. Chem. Phys., 17, 14975-14985, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 19 Dec 2017

Research article | 19 Dec 2017

The single-particle mixing state and cloud scavenging of black carbon: a case study at a high-altitude mountain site in southern China

Guohua Zhang1, Qinhao Lin1,2, Long Peng1,2, Xinhui Bi1, Duohong Chen3, Mei Li4,5, Lei Li4,5, Fred J. Brechtel6, Jianxin Chen7, Weijun Yan7, Xinming Wang1, Ping'an Peng1, Guoying Sheng1, and Zhen Zhou4,5 Guohua Zhang et al.
  • 1State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China
  • 2University of Chinese Academy of Sciences, Beijing 100039, PR China
  • 3State Environmental Protection Key Laboratory of Regional Air Quality Monitoring, Guangdong Environmental Monitoring Center, Guangzhou 510308, PR China
  • 4Institute of Mass Spectrometer and Atmospheric Environment, Jinan University, Guangzhou 510632, PR China
  • 5Guangdong Engineering Research Center for Online Atmospheric Pollution Source Apportionment, Guangzhou 510632, PR China
  • 6Brechtel Manufacturing Inc., Hayward, 94544, CA, USA
  • 7Shaoguan Environmental Monitoring Center, Shaoguan 512026, PR China

Abstract. In the present study, a ground-based counterflow virtual impactor (GCVI) was used to sample cloud droplet residual (cloud RES) particles, while a parallel PM2.5 inlet was used to sample cloud-free or cloud interstitial (cloud INT) particles. The mixing state of black carbon (BC)-containing particles and the mass concentrations of BC in the cloud-free, RES and INT particles were investigated using a single-particle aerosol mass spectrometer (SPAMS) and two aethalometers, respectively, at a mountain site (1690m a. s. l. ) in southern China. The measured BC-containing particles were extensively internally mixed with sulfate and were scavenged into cloud droplets (with number fractions of 0.05–0.45) to a similar (or slightly lower) extent as all the measured particles (0.07–0.6) over the measured size range of 0.1–1.6µm. The results indicate the preferential activation of larger particles and/or that the production of secondary compositions shifts the BC-containing particles towards larger sizes. BC-containing particles with an abundance of both sulfate and organics were scavenged less than those with sulfate but limited organics, implying the importance of the mixing state on the incorporation of BC-containing particles into cloud droplets. The mass scavenging efficiency of BC with an average of 33% was similar for different cloud events independent of the air mass. This is the first time that both the mixing state and cloud scavenging of BC in China have been reported. Our results would improve the knowledge on the concentration, mixing state, and cloud scavenging of BC in the free troposphere.

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The mixing state of black carbon (BC)-containing particles and the mass scavenging efficiency of BC in cloud were investigated at a mountain site (1690 m a.s.l.) in southern China. The measured BC-containing particles were internally mixed extensively with sulfate, and thus the number fraction of scavenged BC-containing particles is close to that of all the measured particles. BC-containing particles with higher fractions of organics were scavenged relatively less.
The mixing state of black carbon (BC)-containing particles and the mass scavenging efficiency of...