Preprints
https://doi.org/10.5194/acp-2022-464
https://doi.org/10.5194/acp-2022-464
 
20 Jul 2022
20 Jul 2022
Status: a revised version of this preprint is currently under review for the journal ACP.

Measurement report: Changes in light absorption and molecular composition of water-soluble humic-like substances during a winter haze bloom-decay process in Guangzhou, China

Chunlin Zou1,3, Tao Cao1,3, Meiju Li1,3, Jianzhong Song1,2,4, Bin Jiang1,2, Wanglu Jia1,2, Jun Li1,2, Xiang Ding1,2, Zhiqiang Yu1,2,4, Gan Zhang1,2, and Ping’an Peng1,2,3,4 Chunlin Zou et al.
  • 1State Key Laboratory of Organic Geochemistry and Guangdong Provincial Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
  • 2CAS Center for Excellence in Deep Earth Science, Guangzhou 510640, China
  • 3University of Chinese Academy of Sciences, Beijing 100049, China
  • 4Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou 510640, China

Abstract. Water-soluble humic-like substances (HULIS) absorb light in near-UV and visible wavelengths and exert significant influence on the atmospheric environment and climate. However, knowledge on HULIS evolution during haze bloom-decay process is limited. Herein, PM2.5 samples were obtained during a winter haze event in Guangzhou, China, and light absorption and molecular composition of HULIS were investigated by UV-vis spectrophotometry and ultrahigh-resolution mass spectrometry. Compared with HULIS in clean days, the absorption coefficients (Abs365) of HULIS in haze days were significantly higher but the mass absorption efficiencies (MAE365) were relatively lower, suggesting diverse and dynamic absorption properties of HULIS during haze episodes. The CHO and CHON compounds were the most abundant components in HULIS, followed by CHOS, CHONS, and CHN. Haze HULIS presented comparatively higher molecular weight, lower aromaticity index (AImod), and higher O/Cw, O/Nw, and O/Sw ratios, indicating that HULIS fractions undergo relatively higher oxidation during haze days than clean days. Moreover, CHON and CHO compounds with high AImod were the major potential chromophores in HULIS and significantly contributed to HULIS light absorption. It's worth noting that the proportions of these chromophores were decreased during haze event, mainly owing to their higher oxidation and longer aging period during haze episode. Besides, accumulated contribution of organic compounds emitted from vehicles and formed from stronger reactions of bio-VOCs also diluted light-absorbing compounds in haze HULIS. These findings help to understand HULIS evolution during haze bloom-decay process in the subtropic region of China.

Chunlin Zou 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-2022-464', Anonymous Referee #1, 10 Aug 2022
  • RC2: 'Comment on acp-2022-464', Anonymous Referee #2, 16 Aug 2022

Chunlin Zou et al.

Data sets

Data for SJ Song, Jianzhong https://doi.org/10.7910/DVN/DYGYQT

Chunlin Zou et al.

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Short summary
In this study, PM2.5 samples were obtained during a winter haze event in Guangzhou, China, and light absorption and molecular composition of HULIS were investigated by UV-vis spectrophotometry and ultrahigh-resolution mass spectrometry. The findings obtained present some differences from the results reported in other regions of China and significantly enhanced our understanding of HULIS evolution during haze bloom-decay process in the subtropic region of South China.
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