Combined Effect of Glycine and Sea Salt on Aerosol Cloud Droplet Activation Predicted by Molecular Dynamics Simulations

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2013-10, Vol.117 (41), p.10746-10752
• Main Authors: Sun, Lu, Hede, Thomas, Tu, Yaoquan, Leck, Caroline, Ågren, Hans
• Format: Article
• Language: English
• Subjects: Activation; Aerosols - chemistry; Albedo; Amino-Acids; Atomic and molecular physics; Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations); Clouds; Clusters; Dimethyl Sulfide; Droplets; Electronic structure of atoms, molecules and their ions: theory; Exact sciences and technology; Glycine; Glycine - chemistry; Gromacs; Linear Constraint Solver; Mathematical analysis; Molecular dynamics; Molecular dynamics and other numerical methods; Molecular Dynamics Simulation; Nanostructure; Particle Mesh Ewald; Physics; Salts - chemistry; Sulfur; Surface Tension; Water
• ISSN: 1089-5639; 1520-5215; 1520-5215
• DOI: 10.1021/jp407538x

The present study illustrates the combined effect of organic and inorganic compounds on cloud droplet nucleation and activation processes representative for the marine environment. Amino acids and sea salt are common marine cloud condensation nuclei (CCN) which act as a prerequisite for growth of cloud droplets. The chemical and physical properties of these CCN play a key role for interfacial properties such as surface tension, which is important for the optical properties of clouds and for heterogeneous reactions. However, there is a lack of detailed information and in situ measurements of surface tension of such nanosized droplets. Here we present a study of the combined effect of zwitterionic glycine (ZGLY) and sea salt in nanosized water droplets using molecular dynamics simulations, where particular emphasis is placed on the surface tension for the nanosized droplets. The critical supersaturation is estimated by the Köhler equation. It is found that dissolved sea salt interacts with ZGLY through a water bridge and weakens the hydrogen bonds among ZGLYs, which has a significant effect on both surface tension and water vapor supersaturation. Clusters of glycine mixed with sea salt deliquesce more efficiently and have higher growth factors.