Title :

A Molecular Scale Investigation of Organic/Inorganic Ion Selectivity at the Air–Liquid Interface

Author(s) :

Ozgurel, Ozge [Auteur]
Physico-Chimie Moléculaire Théorique [PCMT]
Duflot, Denis [Auteur]
Physico-Chimie Moléculaire Théorique [PCMT]
Masella, Michel [Auteur]
Laboratoire de Biologie Structurale et Radiobiologie [LBSR]
Réal, Florent [Auteur]
Physico-Chimie Moléculaire Théorique [PCMT]
Toubin, Celine [Auteur correspondant]
Physico-Chimie Moléculaire Théorique [PCMT]

Journal title :

ACS Earth and Space Chemistry

Pages :

1698-1716

Publisher :

ACS

Publication date :

2022-07-21

ISSN :

2472-3452

HAL domain(s) :

Chimie/Chimie théorique et/ou physique
Physique [physics]/Physique [physics]/Chimie-Physique [physics.chem-ph]

English abstract : [en]

Aerosol particles are known to have a major impact on the climate by directly absorbing and scattering solar radiation and indirectly by acting as cloud condensation nuclei. The main contribution to aerosol emission comes ...
Show more >Aerosol particles are known to have a major impact on the climate by directly absorbing and scattering solar radiation and indirectly by acting as cloud condensation nuclei. The main contribution to aerosol emission comes from the ocean through the production of sea spray aerosols (SSA), which consist of organic and inorganic species, formed in different sizes and shapes, depending on their mixing ratios. The chemical composition of those SSA will be naturally impacted by the chemical composition of the air/water interface. Through complex experiments, it has been shown how surface activity impacts the selective transfer of species from solution to the aerosol phase. While experiments offer a general picture, it is interesting to probe the properties through a systematic and decoupled approach at the molecular level. The present study provides indeed theoretical results to be confronted to reported experimental observations by means of molecular level simulations. We chose a series of linear mono- and dicarboxylates (containing 4, 6, or 8 carbon atoms) being identified as a large fraction of the SSA surface composition, with the possible counterions (Na⁺, K⁺, Ca²⁺, Mg²⁺). Classical molecular dynamics is employed to model the distribution of these ions in a water slab using an ab initio based polarizable force-field model. These calculations allow us to derive some trends on the enrichment of inorganic and organic ions at the liquid–air interface compared to their eventual partitioning in the bulk phase. Indeed, medium to long chain mono- or dicarboxylates predominantly remain at the surface of the aerosol, with inorganic cations accumulating underneath, neutralizing the surface charge. For shorter chains, solvation in the bulk appears more favorable. K⁺ and the dications show a strong ion pairing with the organics, this ion pairing driving their surface vs bulk distribution. In addition, surface tension has been evaluated for the long chain, i.e., having 8 carbons, mono- and dicarboxylates in the presence of the various cations. The surface propensity of the organic chains leads in general to a reduction of surface tension compared to neat water, while mixtures of dicarboxylates and dications give higher values. Finally, these outcomes are discussed in comparison with previous work and within the context of SSA chemistry.Show less >

Language :

Anglais

Popular science :

Non

ANR Project :

Physiques et Chimie de l'Environnement Atmosphérique
ULNE

Collections :

• Laboratoire de Physique des Lasers, Atomes et Molécules (PhLAM) - UMR 8523

Source :

Harvested from HAL