11 Oct 2021

11 Oct 2021

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

Aerodynamic size-resolved composition and cloud condensation nuclei properties of aerosols in Beijing suburban region

Chenjie Yu1,2, Dantong Liu1, Kang Hu1, Ping Tian3, Yangzhou Wu1, Delong Zhao3, Huihui Wu2, Dawei Hu2, Wenbo Guo2, Qiang Li4, Mengyu Huang3, Deping Ding3, and James Allan2,5 Chenjie Yu et al.
  • 1Department of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Zhejiang 310027, China
  • 2Department of Earth and Environmental Sciences, University of Manchester, Manchester M13 9PL, United Kingdom
  • 3Beijing Weather Modification Office, Beijing 100089, China
  • 4Cambustion Ltd China Office, Shanghai 201112, China
  • 5National Centre for Atmospheric Sciences, University of Manchester, Manchester M13 9PL, United Kingdom

Abstract. The size-resolved physiochemical properties of aerosols determine their atmospheric lifetime, cloud interactions, and the deposition rate on human respiratory system, however most atmospheric composition studies tend to evaluate these properties in bulk. This study investigated size-resolved constituents of aerosols on mass and number basis, and their droplet activation properties, by coupling a suite of online measurements with an aerosol aerodynamic classifier (AAC) based on aerodynamic diameter (Da) in Pinggu, a suburb of Beijing. While organic matter accounted for a large fraction of mass, a higher contribution of particulate nitrate at larger sizes (Da > 300 nm) was found under polluted cases. By applying the mixing state of refractory black carbon containing particles (rBCc) and composition-dependent densities, aerosols including rBCc were confirmed nearly spherical at Da > 300 nm. Importantly, the number fraction of rBCc was found to increase with Da at all pollution levels. The number fraction of rBC is found to increase from ~3 % at ~90 nm to ~15 % at ~1000 nm, and this increasing rBC number fraction may be caused by the coagulation during atmospheric aging. The droplet activation diameter at a water supersaturation of 0.2 % was 112 ± 6 nm and 193 ± 41 nm for all particles with Da smaller than 1 μm (PM1) and rBCc respectively. As high as 52 ± 6 % of rBCc and 50 ± 4 % of all PM1 particles in number could be activated under heavy pollution due to enlarged particle size, which could be predicted by applying the volume-mixing of substance hygroscopicity within rBCc. As rBCc contributes to the quantity of aerosols at larger particle size, these thickly coated rBC may contribute to the radiation absorption significantly or act as an important source of cloud condensation nuclei (CCN). This size regime may also exert important health effects due to their higher deposition rate.

Chenjie Yu et al.

Status: open (until 22 Nov 2021)

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Chenjie Yu et al.


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Short summary
In this study, we applied a new technique to investigate the aerosol properties on both mass and number basis, and CCN abilities in a Beijing suburban. The size-resolved aerosol chemical compositions and CCN activation measurement enables a detailed analysis of BC-containing particle hygroscopicity and its size-dependent contribution to the CCN activation. The results presented in this study will implicate the future model and human health studies.