23 Sep 2022
23 Sep 2022
Status: this preprint is currently under review for the journal ACP.

Insoluble lipid film mediates the transfer of soluble saccharides from the sea to the atmosphere: the role of hydrogen bonding

Minglan Xu, Narcisse Tsona Tchinda, Jianlong Li, and Lin Du Minglan Xu et al.
  • Environment Research Institute, Shandong University, Binhai Road 72, Qingdao, 266237, China

Abstract. Saccharides are a large group of organic matter in sea spray aerosol (SSA). Although they can affect climate-related properties of SSA, the mechanism through which saccharides are transferred from bulk seawater to the ocean surface and ultimately into SSA is still debated. Here, the transfer of small soluble saccharides was validated and quantified using a controlled plunging jet sea spray aerosol generator to better understand the wide range of particle properties produced by natural seawater mixed with model organic species, glucose and trehalose. Data show that both soluble saccharides can promote the production of SSA particles. Conversely, the role of the insoluble fatty acid film on the surface greatly reduced the production of SSA. The resulting inorganic-organic mixed particles identified by the transmission electron microscope (TEM) showed typical core-shell morphology. Langmuir model was used to parameterize the adsorption and distribution of saccharide into SSA across the bubble surface, while infrared reflection-absorption spectroscopy (IRRAS) combined with Langmuir isotherms were undertaken to examine the effects of aqueous subphase soluble saccharides on the phase behavior, structure and ordering of insoluble lipid monolayers absorbed at the air/water interface. Changes in alkyl chains and headgroups structure of mixed fatty acid monolayers under different saccharide concentrations in aqueous phase were reported. In seawater solution, the effects of dissolved saccharides on the ordering and organization of fatty acid chains were muted. Hydrogen bond analysis implied that soluble saccharide molecules displaced a large amount of water near the fatty acid polar headgroups. Saccharide-lipid interactions increased with increasing complexity of the saccharide in the order glucose < trehalose. Our results indicate that the interaction between soluble saccharides and insoluble fatty acid molecules through hydrogen bonds is an important component of the sea-air transfer mechanism of saccharides.

Minglan Xu et al.

Status: open (until 04 Nov 2022)

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Minglan Xu et al.

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Latest update: 23 Sep 2022
Short summary
The promotion of soluble saccharides on sea spray aerosol generation and the changes in morphology were observed. On the contrary, the coexistence of surface insoluble fatty acid film and saccharides significantly inhibited the production of SSA. This is the first demonstration that hydrogen bonding mediated by surface-insoluble fatty acids contributes to saccharide transfer in seawater, providing a new mechanism for saccharide enrichment in SSA.