Geochemistry of ocean water bubble spray

The salts in rain, snow, and dew are considered to derive from ocean bubble spray. It was shown by laboratory bubble experiments at varying temperatures, humidities, and salt concentrations that the difference in ion ratios between the spray and the bulk of the solution that is sprayed is in agreement with the requirements of the Gibbs adsorption isotherm if the spray is derived from the surface layer of the bulk solution. Inorganic salts dissolved in ocean water are depleted in the surface of the ocean because the surface tension of their solution rises with their concentration. The gradient of this rise has a characteristic value for each salt and is independent of temperature. For sodium chloride this gradient is 1.85 and for potassium chloride it is 1.50. These and other oceanic salts were tested for changes in ion ratio in the bubble spray of their mixtures. Experiments were performed with sea water and artificial solutions at temperatures ranging from 25° to 130°C. The Gibbs theory predicts quantitatively the ratio changes found in bubble spray at equilibrium conditions only (for ocean environment near 100% humidity). When the sprayed surface is evaporated (subsaturated air, i.e., low humidity), the ratio shift is modified (e.g., enhanced in favor of potassium ions compared with sodium ions). If condensation occurs at the time of bubble spray generation, however, this change in ratio is diminished.