Preprints
https://doi.org/10.5194/acp-2022-218
https://doi.org/10.5194/acp-2022-218
 
08 Apr 2022
08 Apr 2022
Status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Strong light scattering of highly oxygenated organic aerosols impacts significantly on visibility degradation

Li Liu1, Ye Kuang2,3, Miaomiao Zhai2,3, Biao Xue2,3, Yao He2,3, Jun Tao2,3, Biao Luo2,3, Wanyun Xu4, Jiangchuan Tao2,3, Changqin Yin1,7, Fei Li1,5, Hanbing Xu6, Tao Deng1, Xuejiao Deng1, Haobo Tan1, and Min Shao2,3 Li Liu et al.
  • 1Institute of Tropical and Marine Meteorology, China Meteorological Administration, Guangzhou, 510640, China
  • 2Institute for Environmental and Climate Research, Jinan University, Guangzhou, China
  • 3Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Guangzhou, China
  • 4State Key Laboratory of Severe Weather & Key Laboratory for Atmospheric Chemistry, Institute of Atmospheric Composition, Chinese Academy of Meteorological Sciences, Beijing, 100081, China
  • 5Xiamen Key Laboratory of Straits Meteorology, Xiamen Meteorological Bureau, Xiamen, 361012, China
  • 6Experimental Teaching Center, Sun Yat-Sen University, Guangzhou 510275, China
  • 7Shanghai Key Laboratory of Meteorology and Health, Shanghai Meteorological Bureau, Shanghai 200030, China

Abstract. Secondary organic aerosols (SOA) account for a large fraction of atmospheric aerosol mass and play significant roles in visibility impairment by scattering solar radiation. However, comprehensive evaluations of SOA scattering abilities under ambient relative humidity (RH) conditions on the basis of field measurements are still lacking due to the difficulty of simultaneously direct quantifications of SOA scattering efficiency in dry state and SOA water uptake abilities. In this study, field measurements of aerosol chemical and physical properties were conducted in Guangzhou winter (lasted about three months) using a humidified nephelometer system and aerosol chemical speciation monitor. A modified multilinear regression model was proposed to retrieve dry state mass scattering efficiencies (MSE, defined as scattering coefficient per unit aerosol mass) of aerosol components. The more oxidized oxygenated organic aerosol (MOOA) with O / C ratio of 1.17 was identified as the most efficient light scattering aerosol component. On average, 34 % mass contribution of MOOA to total submicron organic aerosol mass contributed 51 % of dry state organic aerosol scattering. Organic aerosol hygroscopicity parameter κOA was quantified through hygroscopicity closure. The highest water uptake ability of MOOA among organic aerosol factors was revealed with κMOOA reaching 0.23, thus further enhanced the fractional contribution of MOOA in ambient organic aerosol scattering. Especially, scattering abilities of MOOA was found to be even higher than that of ammonium nitrate under RH of < 70 % which was identified as the most efficient inorganic scattering aerosol component, demonstrating that MOOA had the strongest scattering abilities in ambient air (average RH of 57 %) during Guangzhou winter. During the observation period, secondary aerosols contributed dominantly to visibility degradation (~70 %) with substantial contributions from MOOA (16 % on average), demonstrating significant impacts of MOOA on visibility degradations. Findings of this study demonstrate that more attentions need to be paid to SOA property changes in future visibility improvement investigations. Also, more comprehensive studies on MOOA physical properties and chemical formation are needed to better parameterize its radiative effects in models and implement targeted control strategies on MOOA precursors for visibility improvement.

Li Liu et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-218', Anonymous Referee #1, 01 May 2022
    • AC1: 'Reply on RC1', Ye Kuang, 24 May 2022
  • RC2: 'Comment on acp-2022-218', Anonymous Referee #2, 21 May 2022
    • AC2: 'Reply on RC2', Ye Kuang, 24 May 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-218', Anonymous Referee #1, 01 May 2022
    • AC1: 'Reply on RC1', Ye Kuang, 24 May 2022
  • RC2: 'Comment on acp-2022-218', Anonymous Referee #2, 21 May 2022
    • AC2: 'Reply on RC2', Ye Kuang, 24 May 2022

Li Liu et al.

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Short summary
Using simultaneous measurements of humidified nephelometer system and aerosol chemical speciation monitor in Guangzhou winter, strongest scattering ability of highly oxygenated organic aerosol (MOOA) among aerosol components considering both their dry state scattering ability and water uptake ability was revealed, leading to significant impacts of MOOA on visibility degradation. This finding has important implications on visibility improvement in China and aerosol radiative effects simulations.
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