Preprints
https://doi.org/10.5194/egusphere-2022-913
https://doi.org/10.5194/egusphere-2022-913
 
16 Sep 2022
16 Sep 2022
Status: this preprint is open for discussion.

Insights into the role of dicarboxylic acid on CCN activity: implications for surface tension and phase state effects

Chun Xiong1, Binyu Kuang1, Xiaolei Ding3, Xiangyu Pei1, Zhengning Xu1, Huan Hu3, and Zhibin Wang1,2,4 Chun Xiong et al.
  • 1College of Environmental and Resource Sciences, Zhejiang University, Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou, China
  • 2ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou, China
  • 3Zhejiang University-University of Illinois at Urbana-Champaign Institute, International Campus, Zhejiang University, Haining 314400, China
  • 4Key Laboratory of Environment Remediation and Ecological Health, Ministry of Education, Zhejiang University, Hangzhou, China

Abstract. Dicarboxylic acids are ubiquitous in atmospheric aerosol particles, but their roles as surfactants in cloud condensation nuclei (CCN) activity remain unclear. In this study, we investigated CCN activity of inorganic salt (sodium chloride and ammonium sulfate) and dicarboxylic acid (including malonic acid (MA), phenylmalonic acid (PhMA), succinic acid (SA), phenylsuccinic acid (PhSA), adipic acid (AA), pimelic acid (PA) and octanedioic acid (OA)) mixed particles with varied organic volume fraction (OVF), and then directly determined their surface tension and phase state at high relative humidity (over 99.5 %) by atomic force microscopy (AFM). Our results showed that CCN derived κCCN of studied dicarboxylic acids ranged in 0.003–0.240. A linearly positive relation between κCCN and solubility was obtained for slightly dissolved species, while negative relation was found between κCCN and molecular volume for highly soluble species. For most inorganic salt/dicarboxylic acid (MA, PhMA, SA, PhSA and PA), a good closure within 30 % relative bias between κCCN and chemistry derived κChem were obtained. However, κCCN values of inorganic salt/AA and inorganic salt/OA systems were surprisingly 0.3–3.0 times higher than κChem, which was attributed to surface tension reduction as AFM results showed that their surface tensions were 20 %–42 % lower than that of water (72 mN m-1). Meanwhile, semisolid phase states were obtained for inorganic salt/AA and inorganic salt/OA and may also affect hygroscopicity closure results. Our study highlights that surface tension reduction should be considered to investigate aerosol-cloud interactions.

Chun Xiong et al.

Status: open (until 28 Oct 2022)

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Short summary
Water surface tension is applied widely in current aerosol-cloud models but could be inappropriate in the presence of atmospheric surfactant. With cloud condensation nuclei (CCN) activity and atomic force microscopy (AFM) measurement results of inorganic salt/dicarboxylic acid mixed particles, we concluded that surface tension reduction and phase state should be carefully considered in aerosol-cloud interactions. Our results could help to decease the uncertainties in climate models.