Identification of Nuclei and Concentrations of Chemical Species in Snow Crystals Sampled at the South Pole

Abstract

A total of 380 electron micrographs and electron diffraction patterns of 93 snow crystal nuclei were analyzed in this observation. The nuclei were identified as mainly clay minerals and sodium chloride particles. The clay mineral nuclei were illite 20%, kaoline 8%, halloysite 4%, verniiculite 3%, and related minerals 24%. For the other nuclei, sodium chloride accounted for 20%, and unidentified nuclei accounted for 5%. Fifteen percent of the snow crystals did not appear to have nuclei. Therefore, all nuclei found in snow crystals were terrestrial substances from oceans and continents. The mass of nuclei was from 10?16 to 10?12 for both clay minerals and sodium chloride. The shapes of snow crystals were single bullets, combinations of bullets, and hexagonal hollow columns. The snow crystals formed at temperatures from ?30 to ?35°C. The snow crystal diameters were from 0.1 to 1.0 mm, and the crystal mass was from 10?8 to 10 ?5 g The mean mass concentration of sodium chloride in snow crystals was 40.6 ppb and that of clay minerals was 15.4 ppb. The sodium chloride nucleus concentration coincided within the experimental error with data taken from the chemical analysis of the South Pole snow cover made by several workers. It was concluded that most of the sodium chloride contained in the South Pole snow cover was due to the sodium chloride nuclei of snow crystals.