Size‐specific composition of aerosols in the El Chichon volcanic cloud

Abstract

A NASA U‐2 research aircraft flew sampling missions in April, May, July, November, and December 1982 aimed at obtaining in situ data in the stratospheric cloud produced from the March‐April 1982 El Chichon eruptions. Aerosol particles were sampled using a quartz crystal microbalance (QCM) cascade impactor. Post flight analyses with scanning electron microscopy (SEM), energy dispersive X‐ray analysis (EDXRA), and Auger spectroscopy provided information on the aerosol composition and morphology. The particles ranged in size from smaller than 0.05 m to larger than 20 m diameter and were quite complex in composition. In the April, May, and July samples the aerosol mass was dominated by magmatic and lithic particles larger than about 3 m. The submicron particles consisted largely of sulfuric acid. Halite particles, believed to be related to a salt dome beneath El Chichon, were collected in the stratosphere in April and May. On the July 23 flight, copper‐zinc oxide particles were collected. In July, November, and December, in addition to the volcanic ash and acid particles, carbon‐rich particles smaller than about 0.1 m aerodynamic diameter were abundant.