Preprints
https://doi.org/10.5194/acp-2022-321
https://doi.org/10.5194/acp-2022-321
 
18 May 2022
18 May 2022
Status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Measurement Report: A new coupled method of pH titration and size-resolved analysis to identify the structure, aging, and source of water-soluble organic carbon

Yuanyuan Qin1, Juanjuan Qin1,2, Xiaobo Wang1, Kang Xiao1, Ting Qi1,6, Yuwei Gao1, Xueming Zhou5, Shaoxuan Shi1, Jingnan Li1, Jingsi Gao3, Ziyin Zhang4, Jihua Tan1, Yang Zhang1, and Rongzhi Chen1 Yuanyuan Qin et al.
  • 1College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China
  • 2Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China
  • 3School of Materials & Environmental Engineering, Shenzhen Polytechnic, Shenzhen, 518000, China
  • 4Institute of Urban Meteorology, China Meteorological Administration, Beijing, 100089, China
  • 5Faculty of Earth Resources, China University of Geosciences, Wuhan, 430074, China
  • 6School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 10049, China

Abstract. Measuring water-soluble organic carbon (WSOC) in aerosols is critical, as WSOC is involved in many key particle-associated chemical reactions. Here, the coupled effects of pH and particle size on the chemical structures (functional groups) and optical properties (UV/fluorescence properties) of WSOC were investigated to explore the structure, aging, and source of these materials. The results showed that the specific UV absorbance at a wavelength of 254 nm (SUVA254) and mass absorption efficiency (MAE365) were higher in smaller particle sizes, revealing the relatively higher aromaticity and more freshness of WSOC in smaller particles. The carboxylic groups tend to be enriched in larger particles, whereas the contribution of phenolic groups was generally higher in smaller particles than that in larger particles. Overall, the chromophores in smaller particles showed a more pronounced pH dependence, revealing that the chromophores in smaller particles were more pH-sensitive. The change in the fluorescence peak position suggested that hydroxyl groups play a leading role in pH-responsive fluorescence in summer, while carboxylic groups in winter. WSOC with sizes of < 0.77 μm mainly originate from primary combustion emissions, and those with sizes of 1.40–2.50 μm primarily originate from secondary formations. Overall, the pH-dependent and particle size-dependent behaviors of aerosols WSOC provide insights into the structure, aging, and source of WSOC, and ultimately contribute to improving the accuracy of assessing the climate effects of WSOC.

Yuanyuan Qin et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-321', Anonymous Referee #1, 23 Jun 2022
  • EC1: 'Comment on acp-2022-321', Irena Grgić, 20 Jul 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-321', Anonymous Referee #1, 23 Jun 2022
  • EC1: 'Comment on acp-2022-321', Irena Grgić, 20 Jul 2022

Yuanyuan Qin et al.

Yuanyuan Qin et al.

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Short summary
Deep interrogation of water-soluble organic carbon (WSOC) in aerosols is critical and challenging because WSOC is involved in many key particle-associated chemical reactions. This work examined how the chemical structure (distribution of functional groups) and optical properties (UV/fluorescence properties) of WSOC were affected by pH and particle size. We found that the pH-dependent and particle size-dependent behaviors could effectively reveal the structure, aging, and source of aerosol WSOC.
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