Hygroscopic Behavior and Chemical composition evolution of Aerosols Generated from Mixture Solutions of Amino Acid (Alanine, Glycine) and NaCl/MgCl2

초록

Individual sea spray aerosols (SSAs) have been identified with water-soluble organic compounds (WSOCs) coatings, in which dissolved free amino acids are one of the major components with glycine and alanine being the most abundant constitutions. Atmospheric amino acids have been confirmed as effective CCN and IN materials. However, the hygroscopicity of amino acids and their mixtures with inorganic salts was not been fully constrained. In the present work, laboratory generated, micrometer sized, pure amino acids (alanine and glycine), their Na(/Mg)-salts, and NaCl(/MgCl2)-amino acids mixture aerosol particles of 3 mixing ratios (molar ratios: 1:1, 2:1, and 1:2), were examined to investigate their hygroscopic behavior and obtain chemical micro-structures using in-situ Raman microspectrometry (RMS). Current observation and Raman analysis showed that pure alanine particles have DRH and ERH higher than 97% and around 70-80%, respectively, while the pure glycine particles exhibited the DRH higher than 97%, and the ERH ranged in 20-50% with the formation of several polymorphs (α, β, and γ phases) after solidification. Mono-Na(/Mg) alanine(/glycine) salts maintained the morphology and structure without any phase transition, i.e., with no ERHs and DRHs, during the hygroscopic process. The hygroscopic measurement of the NaCl(/MgCl2)-amino acids mixture aerosol particles is ongoing, and the interactions between amino acids and inorganic salts will be presented.