Difference in chemical composition of atmospheric sea salt particles produced in the surf zone and on the open sea in Hawaii

Abstract

Cascade impactor samples of atmospheric sea salt particles have been collected at a tower site on the east coast of Hawaii. In an-attempt to differentiate between surf-produced particles and particles produced by bubble bursting on the open sea, samples were collected simultaneously near the tower base and at the top of the tower, 24 meters above sea level. Analyses of the samples by neutron activation for iodine, bromine, and chlorine showed that the total bromine and chlorine concentration was 20–50 times higher at the tower base than at the tower top, whereas total iodine was only twice as high. The I/Cl ratio was a factor of 3–30 higher for samples collected at the tower top. Concentration per cubic meter vs particle size curves for all three halogens were considerably different for samples collected at the two elevations. This vertical gradient shows the large differences between spray particles from waves breaking on the shore and spray particles from waves breaking at sea. Great care must be exercized in selecting coastal sampling sites for the collection of atmospheric sea salt particles which are intended to be representative of particles present in the atmosphere over the open ocean.