Experimental sea salt profiles

A series of determinations was made of the concentration of airborne chloride particles at heights between approximately 1 and 15 meters above the ocean surface, using the sloop Nis Randers as the sampling platform. Analyses were done by the membrane filter technique of J. P. Lodge (1954), which yields both number concentration and particle size. Samples were taken in the general area between Santa Barbara, California, and Santa Catalina Island. As Y. Toba (1965) predicted, there is no clear gradient in concentration over the height interval measured. Number count, geometric mean, and geometric standard deviation were all extremely similar at all heights. Geometric standard deviation was small, rarely exceeding 2.0, and was often as low as 1.5. Geometric mean diameter, expressed as the diameter of an equivalent sphere of pure sodium chloride, was approximately 2 μm. Concentrations ranged over a wide span from a few thousand to a few million particles per cubic meter. Because of the complex geography of the San Pedro channel and adjacent waters, there was no obvious relationship between local wind velocity and particle concentration. A contributing factor may be the difficulty in making measurements in a small boat at wind velocities that cause significant local surface generation of salt particles. Simultaneous collections of smaller particles for electron microscopy showed phosphate to be a consistent minor ingredient, and sulfuric acid and sulfates to be a surprisingly predominant one numerically.