30 Jun 2021

30 Jun 2021

Review status: this preprint is currently under review for the journal ACP.

Hygroscopicity of organic compounds as a function of organic functionality, water solubility, molecular weight and oxidation level

Shuang Han1,2, Juan Hong1,2, Qingwei Luo1,2, Hanbing Xu3, Haobo Tan4,5, Qiaoqiao Wang1,2, Jiangchuan Tao1,2, Yaqing Zhou1,2, Long Peng1,2, Yao He1,2, Jingnan Shi1,2, Nan Ma1,2, Yafang Cheng6,7, and Hang Su6,7 Shuang Han et al.
  • 1Institute for Environmental and Climate Research, Jinan University, Guangzhou, Guangdong 511443, China
  • 2Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Guangzhou, China
  • 3Experimental Teaching Center, Sun Yat-Sen University, Guangzhou 510275, China
  • 4Institute of Tropical and Marine Meteorology/Guangdong Provincial Key Laboratory of Regional Numerical Weather Prediction, CMA, Guangzhou 510640, China
  • 5Foshan Meteorological Service of Guangdong, Foshan 528010, China
  • 6Minerva Research Group, Max Planck Institute for Chemistry, Mainz
  • 7Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany

Abstract. Hygroscopic properties of 23 organics including carboxylic acids, amino acids, sugars and alcohols were characterized using a Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA). We show that hygroscopicity of organics varies widely with different functional groups and organics with additional functional groups are more hygroscopic. However, some compounds sharing the same molecular formula or functionality show quite different hygroscopicity, demonstrating that other physico-chemical properties may contribute to their hygroscopicity as well. If the organics are fully dissolved in water (solubility > 7× 10−1 g/ml), we found that their hygroscopicity is mainly controlled by their molecular weight. For the organics that are not fully dissolved in water (slightly soluble: 5 × 10−4 g/ml < solubility < 7 × 10−1 g/ml), we observed that some of them show no obvious water uptake, which probably due to that they may not deliquesce under our studied conditions up to 90 % RH. The other type of slightly soluble organics is moderate hygroscopic and the larger their solubility the higher their hygroscopicity. Moreover, the hygroscopicity of organics generally increased with O : C ratios, although this relationship is not linear. Hygroscopicity of organic compounds were also predicted by two thermodynamic models using the Extended Aerosol Inorganics Model (E-AIM) and UManSysProp. Both models do not consider phase transition and intermolecular interactions in the simulations and show poor representation of the hygroscopicity for most of the organics.

Shuang Han 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-2021-486', Anonymous Referee #1, 06 Aug 2021
  • RC2: 'Comment on acp-2021-486', Anonymous Referee #2, 09 Aug 2021

Shuang Han et al.


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Short summary
We present the hygroscopicity of 23 organic species with different physico-chemical properties using Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) and comparing the results with two thermodynamic models (E-AIM, UManSysProp). Based on the hygroscopicity parameter κ, the influence of different physico-chemical properties such as functionality, water solubility, molar volume and O:C ratio of organics that potentially drive their hygroscopicity were examined separately.