Microprobe Analysis of Project DUSTORM Hailstone Samples

Abstract

Electron microproble X-ray analysis was used to determine the origin and composition of particulate matter found in hailstones produced during severe storms in the midwestern and central United States. Ratios of aluminum, potassium, calcium, sodium and chlorine X-ray counts to silicon counts were measured for soil samples collected on the ground and compared with ratios for aerosols collected by aircraft and for the particles found in hailstones. Hailstones had higher ratios of K/Si and Ca/Si and lower ratios of Al/Si than the ratios found in soils. Chlorine (absent in dry soil particles) and sodium were found in the hailstones, suggesting that these elements may belong to a compound that is marine in origin.