Ion enrichment in aerosols dispersed from bursting bubbles in aqueous salt solutions

Abstract

It is well known that a large part of the soluble salts found in soils, rivers, and lakes comes from rainwater. These salts are believed to originate as ocean spray carried into the atmosphere from the surface of the seas. Here, tiny bubbles come to the surface and fracture, sending upward aerosols which contain these salts. Studies have been shown that the ratio of the ions present within these aerosols are considerably different from those found in the oceans. The purpose of this investigation was to examine the bubble-bursting process in an effort to determine what is influencing the change in ion ratio. This was done by simulating the bubble-bursting mechanism in very simple salt solutions of concentrations similar to those found in the ocean. Variables examined were concentration, ion character, particle size, and pH. It was found that definite trends in enrichments of one ion species with respect to another in the aerosol phase are related to the ratios of ions in the bulk solution. Also affecting enrichment is the pH of the bulk solution. Enrichments varied with aerosol droplet size in a periodic fashion, with peaks around 1.0 and 6.0 ?m. The results further point to the fact that the ionic double layer is a major factor in the enrichment process in that it influences the ionic equilibria in the thin film of a bubble.