Preprints
https://doi.org/10.5194/acp-2022-831
https://doi.org/10.5194/acp-2022-831
01 Feb 2023
 | 01 Feb 2023
Status: this preprint is currently under review for the journal ACP.

Measurement report: New insights into the mixing structures of black carbon on the eastern Tibetan Plateau: soot redistribution and fractal dimension enhancement by liquid‒liquid phase separation

Qi Yuan, Yuanyuan Wang, Yixin Chen, Siyao Yue, Jian Zhang, Yinxiao Zhang, Liang Xu, Wei Hu, Dantong Liu, Pingqing Fu, Huiwang Gao, and Weijun Li

Abstract. Black carbon (BC, i.e., soot) absorbs radiation and contributes to glacier retreat over the Tibetan Plateau (TP). A lack of comprehensive understanding of the actual mixing state leads to large controversies in the climatic simulation of BC over the TP. In this study, ground-based sampling, electron microscopy analyses, and theoretical calculations were used to investigate the interactions among the liquid‒liquid phase separation (LLPS), soot redistribution in secondary particles, and fractal dimension (Df) of soot particles on the eastern rim of the TP. We found that more than half of the total analysed particles were soot-containing particles. One-third of soot-containing particles showed the LLPS phenomenon between organic matter and inorganic aerosols in individual particles, which further induced soot redistribution. The results show that a larger LLPS particle size, thicker organic coating, and smaller soot particles tended to drag soot from the sulfate core into the organic coating. The Df sequence is ranked as externally mixed soot (1.79 ± 0.09) < sulfate-coated soot (1.84 ± 0.07) < organic-coated soot (1.95 ± 0.06). We concluded that the soot redistribution process and high RH both promoted the morphological compaction of soot particles. This study indicates that soot-containing particles experienced consistent ageing processes that induced a more compact morphology and soot redistribution in the LLPS particles on the remote eastern rim of the TP. Understanding the microscopic changes in aged soot particles could further improve the current climate models and evaluations of BC’s radiative impacts on the eastern TP and similar remote air.

Qi Yuan et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-831', Anonymous Referee #1, 09 Feb 2023
  • RC2: 'Comment on acp-2022-831', Anonymous Referee #2, 13 Mar 2023

Qi Yuan et al.

Data sets

Measurement report: New insights into the mixing structures of black carbon on the eastern Tibetan Plateau: soot redistribution and fractal dimension enhancement by liquid‒liquid phase separation. figshare. Dataset. Yuan, Qi https://doi.org/10.6084/m9.figshare.21988439

Qi Yuan et al.

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Short summary
This study for the first time found large amounts of liquid-liquid phase separation particles with BC redistributing in organic coatings instead of sulfate cores in the eastern TP atmosphere. The entire particle size, OM-coating thickness, and BC size are key factors that affect the BC redistribution process. The BC redistribution process and high RH both promoted the morphological compaction of soot particles.
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