Preprints
https://doi.org/10.5194/acp-2020-1247
https://doi.org/10.5194/acp-2020-1247
24 Mar 2021
 | 24 Mar 2021
Status: this preprint has been withdrawn by the authors.

Physical and chemical constraints on transformation and mass-increase of fine aerosols in northeast Asia

Saehee Lim, Meehye Lee, Paolo Laj, Sang-Woo Kim, Kang-Ho Ahn, Junsoo Gil, Xiaona Shang, Marco Zanatta, and Kyeong-Sik Kang

Abstract. Over the past few decades, northeast Asia has suffered from the extreme levels of PM2.5 (particulate matter with an aerodynamic diameter smaller than 2.5 μm). Despite extensive efforts and the scientific advances in understanding PM2.5 pollution, the fundamental mechanisms responsible for the occurrence of high PM2.5 concentrations have not been comprehensively understood. In this study, we investigated the physical and chemical drivers for the formation and transformation of atmospheric particles using a four-year dataset of nanoparticle number size distributions, PM2.5 chemical composition, gaseous precursors, and meteorological variables in northeast Asia outflows. The empirical orthogonal function (EOF) analyses of size-separated particle numbers extracted two modes representing a burst of nanoparticles (EOF1) and an increase in PM2.5 mass (EOF2) associated with persistent anticyclone and synoptic-scale stagnation, respectively. The vertical structure of the particles demonstrated that the synoptic conditions also affected the daily evolution of boundary layer, promoting either the formation of nanoparticles through deep mixing or conversion into accumulation-mode particles in shallow mixed layers. In the haze-development episode equivalent to EOF2 during the KORUS-AQ (KORea-US Air Quality) campaign, the PM2.5 mass reached 63 μg m−3 with the highest contribution from inorganic constituents, which was accompanied by a thick coating of refractory black carbon (rBC) that linearly increased with condensation-mode particles. This observational evidence suggests that the thick coating of rBC resulted from an active conversion of condensable gases into particle-phase on the BC surface, thereby increasing the mass of the accumulation-mode aerosol. Consequently, this result complies with the strategy to reduce black carbon as a way to effectively mitigate haze pollution as well as climate change in northeast Asia.

This preprint has been withdrawn.

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Saehee Lim, Meehye Lee, Paolo Laj, Sang-Woo Kim, Kang-Ho Ahn, Junsoo Gil, Xiaona Shang, Marco Zanatta, and Kyeong-Sik Kang

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of Lim et al.', Anonymous Referee #2, 29 Apr 2021
  • RC2: 'Comment on acp-2020-1247', Anonymous Referee #1, 10 Jul 2021
  • AC1: 'Comment on acp-2020-1247', Meehye Lee, 15 Sep 2021

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of Lim et al.', Anonymous Referee #2, 29 Apr 2021
  • RC2: 'Comment on acp-2020-1247', Anonymous Referee #1, 10 Jul 2021
  • AC1: 'Comment on acp-2020-1247', Meehye Lee, 15 Sep 2021
Saehee Lim, Meehye Lee, Paolo Laj, Sang-Woo Kim, Kang-Ho Ahn, Junsoo Gil, Xiaona Shang, Marco Zanatta, and Kyeong-Sik Kang
Saehee Lim, Meehye Lee, Paolo Laj, Sang-Woo Kim, Kang-Ho Ahn, Junsoo Gil, Xiaona Shang, Marco Zanatta, and Kyeong-Sik Kang

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Latest update: 10 Dec 2024
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This preprint has been withdrawn.

Short summary
This study identifies the main drivers of the formation and transformation processes of submicron particles and highlights that the thick coating of rBC was a result of active conversion of hygroscopic inorganic salts leading to fine aerosol pollution. Consequently, we suggest BC particles as a key contributor to PM2.5 mass increase, which implies that BC reduction is an effective mitigation against haze pollution as well as climate change in Northeast Asia.
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